Prof. Maria Ekiel-Jeżewska, Ph.D., Dr. Habil.

Department of Biosystems and Soft Matter (ZBiMM)
Division of Complex Fluids (PFPZ)
position: professor IPPT
telephone: (+48) 22 826 12 81 ext.: 227
room: 323
e-mail: mekiel
personal site: http://bluebox.ippt.pan.pl/~mekiel/

Habilitation thesis
2005-09-29Oddziaływania hydrodynamiczne a współczynniki transportu zawiesin 
Professor
2014-02-19Title of professor
Supervision of doctoral theses
1.2016-09-29Gruca Marta  Ruch regularnych układów wielu cząstek oddziałujących hydrodynamicznie w polu grawitacyjnym1255 
2.2012-06-28Myłyk Anna  Dynamika układów wielocząstkowych opadających grawitacyjnie w lepkim płynie648
 

Recent publications
1.Ekiel-Jeżewska M.L., Wajnryb E., Motion of a particle with stick-slip boundary conditions towards a flat interface: hard wall or free surface, Physicochemical Problems of Mineral Processing, ISSN: 1643-1049, DOI: 10.5277/ppmp1849, Vol.54, No.1, pp.203-209, 2018
Abstract:

Motion of a particle with stick-slip boundary conditions towards a hard wall or free surface is investigated in the range of Reynolds numbers much smaller than unity, based on the multipole expansion of the Stokes equations. The slip parameter can be interpreted as a measure of a solid particle roughness or as the effect of a surfactant on the motion of a small spherical non-deformable bubble. The particle friction coefficient is evaluated as a function of the distance from its center to the wall, based on the inverse power series expansion, and the results are used to derive explicit lubrication expressions for the friction coefficient, in a wide range of the slip parameters. It is pointed out that for a very small thickness of the fluid film, the lubrication expressions are more accurate than the series expansion. The drainage time is calculated and analyzed, and estimated in terms of explicit lubrication expressions.

Keywords:

particle, boundary conditions, hard wall, free surface

Affiliations:
Ekiel-Jeżewska M.L.-IPPT PAN
Wajnryb E.-IPPT PAN
2.Cichocki B., Ekiel-Jeżewska M.L., Wajnryb E., Translational and rotational Brownian displacements of colloidal particles of complex shapes, ARCHIVES OF MECHANICS, ISSN: 0373-2029, Vol.69, No.3, pp.257-267, 2017
Abstract:

The exact analytical expressions for the time-dependent cross-correlations of the translational and rotational Brownian displacements of a particle with arbitrary shape were derived by us in [3, 4]. They are in this work applied to construct a method to analyze the Brownian motion of a particle of an arbitrary shape, and to extract accurately the self-diffusion matrix from the measurements of the crosscorrelations, which in turn allows to gain some information on the particle structure. As an example, we apply our new method to analyze the experimental results of D. J. Kraft et al. for the micrometer-sized aggregates of the beads [8]. We explicitly demonstrate that our procedure, based on the measurements of the time-dependent cross-correlations in the whole range of times, allows to determine the self-diffusion (or alternatively the friction matrix) with a much higher precision than the method based only on their initial slopes. Therefore, the analytical time-dependence of the cross-correlations serves as a useful tool to extract information about particle structure from trajectory measurements.

Keywords:

Brownian motion, Smoluchowski equation, hydrodynamic interactions, self-diffusion matrix, friction coefficients, cross-correlations of translational and rotational Brownian displacements

Affiliations:
Cichocki B.-University of Warsaw (PL)
Ekiel-Jeżewska M.L.-IPPT PAN
Wajnryb E.-IPPT PAN
3.Feuillebois F., Ekiel-Jeżewska M.L., Wajnryb E., Sellier A., Bławzdziewicz J., High-frequency effective viscosity of a dilute suspension of particles in Poiseuille flow between parallel walls, JOURNAL OF FLUID MECHANICS, ISSN: 0022-1120, DOI: 10.1017/jfm.2016.378, Vol.800, pp.111-139, 2016
Abstract:

It is shown that the formal expression for the effective viscosity of a dilute suspension of arbitrary-shaped particles in Poiseuille flow contains a novel quadrupole term, besides the expected stresslet. This term becomes important for a very confined geometry. For a high-frequency flow field (in the sense used in Feuillebois et al. (J. Fluid Mech., vol. 764, 2015, pp. 133–147), the suspension rheology is Newtonian at first order in volume fraction. The effective viscosity is calculated for suspensions of N-bead rods and of prolate spheroids with the same length, volume and aspect ratio (up to 6), entrained by the Poiseuille flow between two infinite parallel flat hard walls. The numerical computations, based on solving the Stokes equations, indicate that the quadrupole term gives a significant positive contribution to the intrinsic viscosity [μ] if the distance between the walls is less than ten times the particle width, or less. It is found that the intrinsic viscosity in bounded Poiseuille flow is generally smaller than the corresponding value in unbounded flow, except for extremely narrow gaps when it becomes larger because of lubrication effects. The intrinsic viscosity is at a minimum for a gap between walls of the order of 1.5–2 particle width. For spheroids, the intrinsic viscosity is generally smaller than for chains of beads with the same aspect ratio, but when normalized by its value in the bulk, the results are qualitatively the same. Therefore, a rigid chain of beads can serve as a simple model of an orthotropic particle with a more complicated shape. The important conclusion is that the intrinsic viscosity in shear flow is larger than in the Poiseuille flow between two walls, and the difference is significant even for relatively wide channels, e.g. three times wider than the particle length. For such confined geometries, the hydrodynamic interactions with the walls are significant and should be taken into account.

Keywords:

low-Reynolds-number flows

Affiliations:
Feuillebois F.-Laboratoire d'Informatique pour la Mécanique et les Sciences de l'Ingénieur (FR)
Ekiel-Jeżewska M.L.-IPPT PAN
Wajnryb E.-IPPT PAN
Sellier A.-École Polytechnique (FR)
Bławzdziewicz J.-Texas Tech University (US)
4.Farutin A., Piasecki T., Słowicka A.M., Misbah C., Wajnryb E., Ekiel-Jeżewska M.L., Dynamics of flexible fibers and vesicles in Poiseuille flow at low Reynolds number, SOFT MATTER, ISSN: 1744-683X, DOI: 10.1039/c6sm00819d, Vol.12, pp.7307-7323, 2016
Abstract:

The dynamics of flexible fibers and vesicles in unbounded planar Poiseuille flow at low Reynolds number is shown to exhibit similar basic features, when their equilibrium (moderate) aspect ratio is the same and vesicle viscosity contrast is relatively high. Tumbling, lateral migration, accumulation and shape evolution of these two types of flexible objects are analyzed numerically. The linear dependence of the accumulation position on relative bending rigidity, and other universal scalings are derived from the local shear flow approximation.

Keywords:

Poiseuille flow, Stokes equations, vesicles, flexible fibers

Affiliations:
Farutin A.-Université Grenoble Alpes (FR)
Piasecki T.-IPPT PAN
Słowicka A.M.-IPPT PAN
Misbah C.-CNRS (FR)
Wajnryb E.-IPPT PAN
Ekiel-Jeżewska M.L.-IPPT PAN
5.Cichocki B., Ekiel-Jeżewska M.L., Wajnryb E., Note: Brownian motion of colloidal particles of arbitrary shape, JOURNAL OF CHEMICAL PHYSICS, ISSN: 0021-9606, DOI: 10.1063/1.4942119, Vol.144, pp.076101-1-2, 2016
Abstract:

The analytical expressions for the time-dependent cross correlations of the translational and rotational Brownian displacements of a particle with arbitrary shape are derived. The reference center is arbitrary, and the reference frame is such that the rotational-rotational diffusion tensor is diagonal.

Keywords:

Rotational correlation time, Tensor methods, Brownian motion, Colloidal systems, Matrix equations

Affiliations:
Cichocki B.-University of Warsaw (PL)
Ekiel-Jeżewska M.L.-IPPT PAN
Wajnryb E.-IPPT PAN
6.Feuillebois F., Ekiel-Jeżewska M.L., Wajnryb E., Sellier A., Bławzdziewicz J., High-frequency viscosity of a dilute suspension of elongated particles in a linear shear flow between two walls, JOURNAL OF FLUID MECHANICS, ISSN: 0022-1120, DOI: 10.1017/jfm.2014.690, Vol.764, pp.133-147, 2015
Abstract:

A general expression for the effective viscosity of a dilute suspension of arbitrary-shaped particles in linear shear flow between two parallel walls is derived in terms of the induced stresslets on particles. This formula is applied to N-bead rods and to prolate spheroids with the same length, aspect ratio and volume. The effective viscosity of non-Brownian particles in a periodic shear flow is considered here. The oscillating frequency is high enough for the particle orientation and centre-of-mass distribution to be practically frozen, yet small enough for the flow to be quasi-steady. It is known that for spheres, the intrinsic viscosity [μ] increases monotonically when the distance H between the walls is decreased. The dependence is more complex for both types of elongated particles. Three regimes are theoretically predicted here: (i) a ‘weakly confined’ regime (for H>l, where l is the particle length), where [μ] is slightly larger for smaller H; (ii) a ‘semi-confined’ regime, when H becomes smaller than l, where [μ] rapidly decreases since the geometric constraints eliminate particle orientations corresponding to the largest stresslets; (iii) a ‘strongly confined’ regime when H becomes smaller than 2–3 particle widths d, where [μ] rapidly increases owing to the strong hydrodynamic coupling with the walls. In addition, for sufficiently slender particles (with aspect ratio larger than 5–6) there is a domain of narrow gaps for which the intrinsic viscosity is smaller than that in unbounded fluid.

Keywords:

complex fluids, low-Reynolds-number flows, suspensions

Affiliations:
Feuillebois F.-Laboratoire d'Informatique pour la Mécanique et les Sciences de l'Ingénieur (FR)
Ekiel-Jeżewska M.L.-IPPT PAN
Wajnryb E.-IPPT PAN
Sellier A.-École Polytechnique (FR)
Bławzdziewicz J.-Texas Tech University (US)
7.Bukowicki M., Gruca M., Ekiel-Jeżewska M.L., Dynamics of elastic dumbbells sedimenting in a viscous fuid: oscillations and hydrodynamic repulsion, JOURNAL OF FLUID MECHANICS, ISSN: 0022-1120, DOI: 10.1017/jfm.2015.31, Vol.767, pp.95-108, 2015
Abstract:

Hydrodynamic interactions between two identical elastic dumbbells settling under gravity in a viscous fluid at low Reynolds number are investigated using the point-particle model. The evolution of a benchmark initial configuration is studied, in which the dumbbells are vertical and their centres are aligned horizontally. Rigid dumbbells and pairs of separate beads starting from the same positions tumble periodically while settling. We find that elasticity (which breaks the time-reversal symmetry of the motion) significantly affects the system dynamics. This is remarkable when taking into account that elastic forces are always much smaller than gravity. We observe oscillating motion of the elastic dumbbells, which tumble and change their length non-periodically. Independently of the value of the spring constant, a horizontal hydrodynamic repulsion appears between the dumbbells: their centres of mass move apart from each other horizontally. This motion is fast for moderate values of the spring constant k, and slows down when k tends to zero or to infinity; in these limiting cases we recover the periodic dynamics reported in the literature. For moderate values of the spring constant, and different initial configurations, we observe the existence of a universal time-dependent solution to which the system converges after an initial relaxation phase. The tumbling time and the width of the trajectories in the centre-of-mass frame increase with time. In addition to its fundamental significance, the benchmark solution presented here is important to understanding general features of systems with a larger number of elastic particles, in regular and random configurations.

Keywords:

complex fluids, low-Reynolds-number flows, Stokesian dynamics

Affiliations:
Bukowicki M.-IPPT PAN
Gruca M.-IPPT PAN
Ekiel-Jeżewska M.L.-IPPT PAN
8.Kuei S., Słowicka A.M., Ekiel-Jeżewska M.L., Wajnryb E., Stone H.A., Dynamics and topology of a flexible chain: knots in steady shear flow, NEW JOURNAL OF PHYSICS, ISSN: 1367-2630, DOI: 10.1088/1367-2630/17/5/053009, Vol.17, pp.053009-1-15, 2015
Abstract:

We use numerical simulations of a bead–spring model chain to investigate the evolution of the conformations of long and flexible elastic fibers in a steady shear flow. In particular, for rather open initial configurations, and by varying a dimensionless elastic parameter, we identify two distinct conformational modes with different final size, shape, and orientation. Through further analysis we identify slipknots in the chain. Finally, we provide examples of initial configurations of an 'open' trefoil knot that the flow unknots and then knots again, sometimes repeating several times.

Keywords:

knots, low Reynolds number flows, multipole method

Affiliations:
Kuei S.-Princeton University (US)
Słowicka A.M.-IPPT PAN
Ekiel-Jeżewska M.L.-IPPT PAN
Wajnryb E.-IPPT PAN
Stone H.A.-Princeton University (US)
9.Ekiel-Jeżewska M.L., Felderhof B.U., Hydrodynamic interactions between a sphere and a number of small particles, JOURNAL OF CHEMICAL PHYSICS, ISSN: 0021-9606, DOI: 10.1063/1.4904981, Vol.142, pp.014904-1-5, 2015
Abstract:

Exact expressions are derived for the pair and three-body hydrodynamic interactions between a sphere and a number of small particles immersed in a viscous incompressible fluid. The analysis is based on the Stokes equations of low Reynolds number hydrodynamics. The results follow by a combination of the solutions for flow about a sphere with no-slip boundary condition derived by Stokes and Kirchhoff and the result derived by Oseen for the Green tensor of Stokes equations in the presence of a fixed sphere.

Keywords:

Hydrodynamics, Tensor methods, Stokes flows, Boundary value problems, Torque

Affiliations:
Ekiel-Jeżewska M.L.-IPPT PAN
Felderhof B.U.-RWTH Aachen University (DE)
10.Słowicka A., Wajnryb E., Ekiel-Jeżewska M., Dynamics of flexible fibers in shear flow, JOURNAL OF CHEMICAL PHYSICS, ISSN: 0021-9606, DOI: 10.1063/1.4931598, Vol.143, pp.124904-1-6, 2015
Abstract:

Dynamics of flexible non-Brownian fibers in shear flow at low-Reynolds-number are analyzed numerically for a wide range of the ratios A of the fiber bending force to the viscous drag force. Initially, the fibers are aligned with the flow, and later they move in the plane perpendicular to the flow vorticity. A surprisingly rich spectrum of different modes is observed when the value of A is systematically changed, with sharp transitions between coiled and straightening out modes, period-doubling bifurcations from periodic to migrating solutions, irregular dynamics, and chaos.

Keywords:

Shear flows, Chaotic dynamics, Vortex dynamics, Numerical solutions, Periodic solutions

Affiliations:
Słowicka A.-IPPT PAN
Wajnryb E.-IPPT PAN
Ekiel-Jeżewska M.-IPPT PAN
11.Sonn-Segev A., Bławzdziewicz J., Wajnryb E., Ekiel-Jeżewska M.L., Diamant H., Roichman Y., Structure and dynamics of a layer of sedimented particles, JOURNAL OF CHEMICAL PHYSICS, ISSN: 0021-9606, DOI: 10.1063/1.4928644, Vol.143, pp.074704-1-14, 2015
Abstract:

We investigate experimentally and theoretically thin layers of colloid particles held adjacent to a solid substrate by gravity. Epifluorescence, confocal, and holographic microscopy, combined with Monte Carlo and hydrodynamic simulations, are applied to infer the height distribution function of particles above the surface, and their diffusion coefficient parallel to it. As the particle area fraction is increased, the height distribution becomes bimodal, indicating the formation of a distinct second layer. In our theory, we treat the suspension as a series of weakly coupled quasi-two-dimensional layers in equilibrium with respect to particle exchange. We experimentally, numerically, and theoretically study the changing occupancies of the layers as the area fraction is increased. The decrease of the particle diffusion coefficient with concentration is found to be weakened by the layering. We demonstrate that particle polydispersity strongly affects the properties of the sedimented layer, because of particle size segregation due to gravity.

Keywords:

colloidal particles, gravity, horizontal wall, two-dimensional layers, diffusion, height distribution function

Affiliations:
Sonn-Segev A.-Tel Aviv University (IL)
Bławzdziewicz J.-Texas Tech University (US)
Wajnryb E.-IPPT PAN
Ekiel-Jeżewska M.L.-IPPT PAN
Diamant H.-Tel Aviv University (IL)
Roichman Y.-Tel Aviv University (IL)
12.Cichocki B., Ekiel-Jeżewska M.L., Wajnryb E., Brownian motion of a particle with arbitrary shape, JOURNAL OF CHEMICAL PHYSICS, ISSN: 0021-9606, DOI: 10.1063/1.4921729, Vol.142, pp.214902-1-9, 2015
Abstract:

rownian motion of a particle with an arbitrary shape is investigated theoretically. Analytical expressions for the time-dependent cross-correlations of the Brownian translational and rotational displacements are derived from the Smoluchowski equation. The role of the particle mobility center is determined and discussed.

Keywords:

Tensor methods, Brownian motion, Matrix theory, Rotational correlation time, Eigenvalues

Affiliations:
Cichocki B.-University of Warsaw (PL)
Ekiel-Jeżewska M.L.-IPPT PAN
Wajnryb E.-IPPT PAN
13.Gruca M., Bukowicki M., Ekiel-Jeżewska M.L., Periodic and quasiperiodic motions of many particles falling in a viscous fluid, PHYSICAL REVIEW E, ISSN: 1539-3755, DOI: 10.1103/PhysRevE.92.023026, Vol.92, pp.023026-1-10, 2015
Abstract:

The dynamics of regular clusters of many nontouching particles falling under gravity in a viscous fluid at low Reynolds number are analyzed within the point-particle model. The evolution of two families of particle configurations is determined: two or four regular horizontal polygons (called “rings”) centered above or below each other. Two rings fall together and periodically oscillate. Four rings usually separate from each other with chaotic scattering. For hundreds of thousands of initial configurations, a map of the cluster lifetime is evaluated in which the long-lasting clusters are centered around periodic solutions for the relative motions, and they are surrounded by regions of chaotic scattering in a similar way to what was observed by Janosi et al. [Phys. Rev. E. 56, 2858 (1997)] for three particles only. These findings suggest that we should consider the existence of periodic orbits as a possible physical mechanism of the existence of unstable clusters of particles falling under gravity in a viscous fluid.

Keywords:

Stokes equations, particle clusters, sedimentation, chaotic scattering, periodic orbits

Affiliations:
Gruca M.-IPPT PAN
Bukowicki M.-IPPT PAN
Ekiel-Jeżewska M.L.-IPPT PAN
14.Cichocki B., Ekiel-Jeżewska M.L., Wajnryb E., Hydrodynamic radius approximation for spherical particles suspended in a viscous fluid: Influence of particle internal structure and boundary, JOURNAL OF CHEMICAL PHYSICS, ISSN: 0021-9606, DOI: 10.1063/1.4871498, Vol.140, pp.164902-1-7, 2014
Abstract:

Systems of spherical particles moving in Stokes flow are studied for different particle internal structures and boundaries, including the Navier-slip model. It is shown that their hydrodynamic interactions are well described by treating them as solid spheres of smaller hydrodynamic radii, which can be determined from measured single-particle diffusion or intrinsic viscosity coefficients. Effective dynamics of suspensions made of such particles is quite accurately described by mobility coefficients of the solid particles with the hydrodynamic radii, averaged with the unchanged direct interactions between the particles.

Keywords:

hydrodynamic radius, Stokes equations

Affiliations:
Cichocki B.-University of Warsaw (PL)
Ekiel-Jeżewska M.L.-IPPT PAN
Wajnryb E.-IPPT PAN
15.Ekiel-Jeżewska M.L., Class of periodic and quasiperiodic trajectories of particles settling under gravity in a viscous fluid, PHYSICAL REVIEW E, ISSN: 1539-3755, DOI: 10.1103/PhysRevE.90.043007, Vol.90, pp.043007-1-10, 2014
Abstract:

We investigate regular configurations of a small number of non-Brownian particles settling under gravity in a viscous fluid. The particles do not touch each other and can move relative to each other. The dynamics is analyzed in the point-particle approximation. A family of regular configurations is found with periodic oscillations of all the settling particles. The oscillations are shown to be robust under some out-of-phase rearrangements of the particles. In the presence of an additional particle above such a regular configuration, the particle periodic trajectories are horizontally repelled from the symmetry axis, and flattened vertically. The results are used to propose a mechanism of how a spherical cloud, made of a large number of particles distributed at random, evolves and destabilizes.

Keywords:

Stokes equations, sedimentation, particle cluster, suspension drop, periodic orbits

Affiliations:
Ekiel-Jeżewska M.L.-IPPT PAN
16.Pasol L., Martin M., Ekiel-Jeżewska M.L., Wajnryb E., Bławzdziewicz J., Feuillebois F., Corrigendum to ‘‘Motion of a sphere parallel to plane walls in a Poiseuille flow. Application to field-flow fractionation and hydrodynamic chromatography’’, CHEMICAL ENGINEERING SCIENCE, ISSN: 0009-2509, DOI: 10.1016/j.ces.2012.12.020, Vol.90, pp.51-52, 2013
Abstract:

The authors report that there is a confusion in the definition of the friction factors, pffp, pccp in Pasol et al. (2011).

Keywords:

friction factors, Poiseuille flow, spherical particle, field-flow fractionation, hydrodynamic chromatotography

Affiliations:
Pasol L.-Université Pierre et Marie Curie (FR)
Martin M.-CNRS (FR)
Ekiel-Jeżewska M.L.-IPPT PAN
Wajnryb E.-IPPT PAN
Bławzdziewicz J.-Texas Tech University (US)
Feuillebois F.-Laboratoire d'Informatique pour la Mécanique et les Sciences de l'Ingénieur (FR)
17.Słowicka A.M., Wajnryb E., Ekiel-Jeżewska M.L., Lateral migration of flexible fibers in Poiseuille flow between two parallel planar solid walls, EUROPEAN PHYSICAL JOURNAL E, ISSN: 1292-8941, DOI: 10.1140/epje/i2013-13031-2, Vol.36, pp.1-12, 2013
Abstract:

Dynamics of non-Brownian flexible fibers in Poiseuille flow between two parallel planar solid walls is evaluated from the Stokes equations which are solved numerically by the multipole method. Fibers migrate towards a critical distance from the wall zc, which depends significantly on the fiber length N and bending stiffness A. This effect can be used to sort fibers. Three types of accumulation are found, depending on a shear-to-bending parameter Γ. In the first type, stiff fibers deform only a little and accumulate close to the wall, where their tendency to drift away from the channel is balanced by the repulsive hydrodynamic interaction with the wall. In the second type, flexible fibers deform significantly and accumulate far from the wall. In both types, the fiber shapes at the accumulation positions are repeatable, while in the third type, they are very compact and non-repeatable. The difference between the second and third accumulation types is a special case of the difference between the regular and irregular modes for the dynamics of migrating fibers. At the regular mode, far from walls, the fiber tumbling frequency satisfies Jeffery’s expression, with the local shear rate and the aspect ratio close to N.

Keywords:

Self-organisation, Supramolecular assemblies

Affiliations:
Słowicka A.M.-IPPT PAN
Wajnryb E.-IPPT PAN
Ekiel-Jeżewska M.L.-IPPT PAN
18.Cichocki B., Ekiel-Jeżewska M.L., Wajnryb E., Short-time dynamics and high-frequency rheology of suspensions of spherical core-shell particles with thin-shells, COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS, ISSN: 0927-7757, DOI: 10.1016/j.colsurfa.2012.10.053, Vol.418, pp.22-28, 2013
Abstract:

Short-time dynamics and high-frequency rheology for suspensions of non-overlapping core–shell particles with thin shells were analyzed. In the thin-shell limit, the single-particle scattering coefficients were derived and shown to define a unique effective radius. This result was used to justify theoretically (in the thin-shell limit) the accuracy of the annulus approximation with the inner radius equal to the effective hydrodynamic radius of the core–shell particle. The two-particle virial expansion of the translational and rotational self-diffusion, sedimentation and viscosity was performed. The virial coefficients were evaluated and shown to be accurately approximated by the effective annulus model, in contrast to the imprecise effective hard sphere model.

Keywords:

Stokes equations, Core–shell particles, Permeable medium

Affiliations:
Cichocki B.-University of Warsaw (PL)
Ekiel-Jeżewska M.L.-IPPT PAN
Wajnryb E.-IPPT PAN
19.Ekiel-Jeżewska M.L., Nasi dziadkowie jako uczniowie i nauczyciele, Rocznik Mińskomazowiecki, ISSN: 1232-633X, Vol.21, pp.245-258, 2013
Abstract:

Każdy z nas ma własne wspomnienia szkolne, a także słyszał opowieści o nauce rodziców i dziadków. Wyselekcjonujmy z nich takie, które dotyczą ważnych elementów kształcenia i pokażmy innym. Porozmawiajmy o tym, na czym polega takie uczenie się, jakiego potrzebujemy i za jakim tęsknimy. Przykładem może służyć rozmowa, która zaczęła się od pokazania osobistych pamiątek szkolnych kilku rodzin z regionu Mińska Mazowieckiego i przywołania wspomnień związanych z najlepszymi tradycjami i historią polskiej edukacji w I połowie XX wieku. Eksponaty te od 22 listopada 2012 do 10 marca 2013 r. można było zobaczyć w Muzeum Ziemi Mińskiej na wystawie „Nasi dziadkowie jako uczniowie i nauczyciele”. Artykuł opowiada o tej wystawie i relacjonuje niektóre zebrane przy tej okazji wspomnienia.

Keywords:

nauka, edukacja, tradycje

Affiliations:
Ekiel-Jeżewska M.L.-IPPT PAN
20.Abade G.C., Cichocki B., Ekiel-Jeżewska M.L., Naegele G., Wajnryb E., Diffusion, sedimentation, and rheology of concentrated suspensions of core-shell particles, JOURNAL OF CHEMICAL PHYSICS, ISSN: 0021-9606, DOI: 10.1063/1.3689322, Vol.136, pp.104902-1-16, 2012
Abstract:

Short-time dynamic properties of concentrated suspensions of colloidal core-shell particles are studied using a precise force multipole method which accounts for many-particle hydrodynamic interactions. A core-shell particle is composed of a rigid, spherical dry core of radius a surrounded by a uniformly permeable shell of outer radius b and hydrodynamic penetration depth κ−1. The solvent flow inside the permeable shell is described by the Brinkman-Debye-Bueche equation, and outside the particles by the Stokes equation. The particles are assumed to interact non-hydrodynamically by a hard-sphere no-overlap potential of radius b. Numerical results are presented for the high-frequency shear viscosity, η∞, sedimentation coefficient, K, and the short-time translational and rotational self-diffusion coefficients, D t and D r . The simulation results cover the full three-parametric fluid-phase space of the composite particle model, with the volume fraction extending up to 0.45, and the whole range of values for κb, and a/b. Many-particle hydrodynamic interaction effects on the transport properties are explored, and the hydrodynamic influence of the core in concentrated systems is discussed. Our simulation results show that for thin or hardly permeable shells, the core-shell systems can be approximated neither by no-shell nor by no-core models. However, one of our findings is that for κ(b − a) ≳ 5, the core is practically not sensed any more by the weakly penetrating fluid. This result is explained using an asymptotic analysis of the scattering coefficients entering into the multipole method of solving the Stokes equations. We show that in most cases, the influence of the core grows only weakly with increasing concentration.

Keywords:

core-shell particles, suspension, diffusion, sedimentation, effective viscosity

Affiliations:
Abade G.C.-Universidade de Brasilia (BR)
Cichocki B.-University of Warsaw (PL)
Ekiel-Jeżewska M.L.-IPPT PAN
Naegele G.-other affiliation
Wajnryb E.-IPPT PAN
21.Cichocki B., Ekiel-Jeżewska M.L., Wajnryb E., Communication: Translational Brownian motion for particles of arbitrary shape, JOURNAL OF CHEMICAL PHYSICS, ISSN: 0021-9606, DOI: 10.1063/1.3689842, Vol.136, pp.071102-1-4, 2012
Abstract:

A single Brownian particle of arbitrary shape is considered. The time-dependent translational mean square displacement W(t) of a reference point at this particle is evaluated from the Smoluchowski equation. It is shown that at times larger than the characteristic time scale of the rotational Brownian relaxation, the slope of W(t) becomes independent of the choice of a reference point. Moreover, it is proved that in the long-time limit, the slope of W(t) is determined uniquely by the trace of the translational-translational mobility matrix μtt evaluated with respect to the hydrodynamic center of mobility. The result is applicable to dynamic light scattering measurements, which indeed are performed in the long-time limit.

Keywords:

translational and rotational Brownian motion, mean square displacement, particle of arbitrary shape, mobility center

Affiliations:
Cichocki B.-University of Warsaw (PL)
Ekiel-Jeżewska M.L.-IPPT PAN
Wajnryb E.-IPPT PAN
22.Słowicka A.M., Ekiel-Jeżewska M.L., Sadlej K., Wajnryb E., Dynamics of fibers in a wide microchannel, JOURNAL OF CHEMICAL PHYSICS, ISSN: 0021-9606, DOI: 10.1063/1.3678852, Vol.136, pp.044904-1-8, 2012
Abstract:

Dynamics of single flexible non-Brownian fibers, tumbling in a Poiseuille flow between two parallel solid plane walls, is studied with the use of the HYDROMULTIPOLE numerical code, based on the multipole expansion of the Stokes equations, corrected for lubrication. Fibers, which are closer to a wall, more flexible (less stiff) or longer, deform more significantly and, for a wide range of the system parameters, they faster migrate towards the middle plane of the channel. For the considered systems, fiber velocity along the flow is only slightly smaller than (and can be well approximated by) the Poseuille flow velocity at the same position. In this way, the history of a fiber migration across the channel is sufficient to determine with a high accuracy its displacement along the flow.

Keywords:

Stokes equations, flexible fiber, Poiseuille flow, solid walls

Affiliations:
Słowicka A.M.-IPPT PAN
Ekiel-Jeżewska M.L.-IPPT PAN
Sadlej K.-IPPT PAN
Wajnryb E.-IPPT PAN
23.Adamczyk Z., Cichocki B., Ekiel-Jeżewska M.L., Słowicka A., Wajnryb E., Wasilewska M., Fibrinogen conformations and charge in electrolyte solutions derived from DLS and dynamic viscosity measurements, JOURNAL OF COLLOID AND INTERFACE SCIENCE, ISSN: 0021-9797, DOI: 10.1016/j.jcis.2012.07.010, Vol.385, pp.244-257, 2012
Abstract:

Hydrodynamic properties of fibrinogen molecules were theoretically calculated. Their shape was approximated by the bead model, considering the presence of flexible side chains of various length and orientation relative to the main body of the molecule. Using the bead model, and the precise many-multipole method of solving the Stokes equations, the mobility coefficients for the fibrinogen molecule were calculated for arbitrary orientations of the arms whose length was varied between 12 and 18 nm. Orientation averaged hydrodynamic radii and intrinsic viscosities were also calculated by considering interactions between the side arms and the core of the fibrinogen molecule. Whereas the hydrodynamic radii changed little with the interaction magnitude, the intrinsic viscosity exhibited considerable variation from 30 to 60 for attractive and repulsive interactions, respectively. These theoretical results were used for the interpretation of experimental data derived from sedimentation and diffusion coefficient measurements as well as dynamic viscosity measurements. Optimum dimensions of the fibrinogen molecule derived in this way were the following: the contour length 84.7 nm, the side arm length 18 nm, and the total volume 470 nm3, which gives 16% hydration (by volume). Our calculations enabled one to distinguish various conformational states of the fibrinogen molecule, especially the expanded conformation, prevailing for pH < 4 and lower ionic strength, characterized by high intrinsic viscosity of 50 and the hydrodynamic radius of 10.6 nm. On the other hand, for the physiological condition, that is, pH = 7.4 and the ionic strength of 0.15 M NaCl, the semi-collapsed conformation dominates. It is characterized by the average angle equal to = 55, intrinsic viscosity of 35, and the hydrodynamic radius of 10 nm. Additionally, the interaction energy between the arms and the body of the molecule was predicted to be 4 kT units, confirming that they are oppositely charged than the central nodule. Results obtained in our work confirm an essential role of the side chains responsible for a highly anisotropic charge distribution in the fibrinogen molecule. These finding can be exploited to explain anomalous adsorption of fibrinogen on various surfaces.

Keywords:

Bead model of fibrinogen, Charge distribution over fibrinogen, Conformations of fibrinogen molecule, Fibrinogen molecule conformations, Hydrodynamic radius of fibrinogen, Viscosity of fibrinogen solutions

Affiliations:
Adamczyk Z.-Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences (PL)
Cichocki B.-University of Warsaw (PL)
Ekiel-Jeżewska M.L.-IPPT PAN
Słowicka A.-IPPT PAN
Wajnryb E.-IPPT PAN
Wasilewska M.-other affiliation
24.Ekiel-Jeżewska M.L., System kształcenia Komisji Edukacji Narodowej, Rozprawy z dziejów oświaty, ISSN: 0080-4754, Vol.XLIX, pp.55-110, 2012
Abstract:

In a successfully developing system, goal, principles and processes are coupled with each other and with a continuous increase of knowledge. Analyzing these relations, Wilson, Barsky and Daviss proposed universal criteria to assess progress of systemic changes. These criteria can be applied to development of a modern technology or science, as well as to education reforms. The goal of this work is to apply these criteria to analyze effectiveness of the schooling system created by the Polish Commission of the National Education (KEN). We have shown how the overarching goal of education – economical and political development of Poland – was consistent with the KEN basic principles: common goals, freedom and autonomy, ownership of accumulated knowledge. We have demonstrated how KEN kept alive six processes inherent to successful system reforms: knowledge accumulation, sustained professional development within a recognized hierarchy of practitioner’s expertise and transmission of this expertise to others, design of complex entities, improvement of quality, diffusion of innovations, and redesign. In this way, we have provided an example how a similar assessment can be performed for modern educational initiatives, programs, systems and reforms, in contrast to common evaluation of individual teachers and students. Following the best Polish educational tradition, we have reminded that, nowadays, we need to rethink what does it mean to learn and teach productively, and what should be the overarching goal of schooling in the society of the XXI century.

Keywords:

Komisja Edukacji Narodowej, reforma edukacji, procesy charakteryzujące rozwój systemu, sprzężecie celu, procesów, zasad i wiedzy w skutecznym systemie

Affiliations:
Ekiel-Jeżewska M.L.-IPPT PAN
25.Pasol L., Martin M., Ekiel-Jeżewska M.L., Wajnryb E., Bławzdziewicz J., Feuillebois F., Motion of a sphere parallel to plane walls in a Poiseuille flow. Application to field-flow fractionation and hydrodynamic chromatography, CHEMICAL ENGINEERING SCIENCE, ISSN: 0009-2509, DOI: 10.1016/j.ces.2011.05.033, Vol.66, pp.4078-4089, 2011
Abstract:

The motion of a solid spherical particle entrained in a Poiseuille flow between parallel plane walls has various applications to separation methods, like field-flow fractionation and hydrodynamic chromatography. Various handy formulae are presented here to describe the particle motion, with these applications in mind. Based on the assumption of a low Reynolds number, the multipole expansion method coupled to a Cartesian representation is applied to provide accurate results for various friction factors in the motion of a solid spherical particle embedded in a viscous fluid between parallel planes. Accurate results for the velocity of a freely moving solid spherical particle are then obtained. These data are fitted so as to obtain handy formulae, providing e.g. the velocity of the freely moving sphere with a 1% error. For cases where the interaction with a single wall is sufficient, simpler fitting formulae are proposed, based on earlier results using the bispherical coordinates method. It appears that the formulae considering only the interaction with a nearest wall are applicable for a surprisingly wide range of particle positions and channel widths. As an example of application, it is shown how in hydrodynamic chromatography earlier models ignoring the particle-wall hydrodynamic interactions fail to predict the proper choice of channel width for a selective separation. The presented formulae may also be used for modeling the transport of macromolecular or colloidal objects in microfluidic systems.

Keywords:

Creeping flow, Particle, Suspension, Interaction with walls, Separations, Selectivity

Affiliations:
Pasol L.-Université Pierre et Marie Curie (FR)
Martin M.-CNRS (FR)
Ekiel-Jeżewska M.L.-IPPT PAN
Wajnryb E.-IPPT PAN
Bławzdziewicz J.-Texas Tech University (US)
Feuillebois F.-Laboratoire d'Informatique pour la Mécanique et les Sciences de l'Ingénieur (FR)
26.Abade G.C., Cichocki B., Ekiel-Jeżewska M.L., Nägele G., Wajnryb E., Rotational and translational self-diffusion in concentrated suspensions of permeable particles, JOURNAL OF CHEMICAL PHYSICS, ISSN: 0021-9606, DOI: 10.1063/1.3604813, Vol.134, pp.244903-1-7, 2011
Abstract:

In our recent work on concentrated suspensions of uniformly porous colloidal spheres with excluded volume interactions, a variety of short-time dynamic properties were calculated, except for the rotational self-diffusion coefficient. This missing quantity is included in the present paper. Using a precise hydrodynamic force multipole simulation method, the rotational self-diffusion coefficient is evaluated for concentrated suspensions of permeable particles. Results are presented for particle volume fractions up to 45% and for a wide range of permeability values. From the simulation results and earlier results for the first-order virial coefficient, we find that the rotational self-diffusion coefficient of permeable spheres can be scaled to the corresponding coefficient of impermeable particles of the same size. We also show that a similar scaling applies to the translational self-diffusion coefficient considered earlier. From the scaling relations, accurate analytic approximations for the rotational and translational self-diffusion coefficients in concentrated systems are obtained, useful to the experimental analysis of permeable-particle diffusion. The simulation results for rotational diffusion of permeable particles are used to show that a generalized Stokes-Einstein-Debye relation between rotational self-diffusion coefficient and high-frequency viscosity is not satisfied.

Keywords:

self-diffusion, permeable particles, concentrated suspensions

Affiliations:
Abade G.C.-Universidade de Brasilia (BR)
Cichocki B.-University of Warsaw (PL)
Ekiel-Jeżewska M.L.-IPPT PAN
Nägele G.-Forschugszentrum Jülich, Institute of Complex Systems (DE)
Wajnryb E.-IPPT PAN
27.Ekiel-Jeżewska M.L., Wajnryb E., Lifetime of a cluster of spheres settling under gravity in Stokes flow, PHYSICAL REVIEW E, ISSN: 1539-3755, DOI: 10.1103/PhysRevE.83.067301, Vol.83, pp.067301-1-4, 2011
Abstract:

The evolution of a cluster of three identical nontouching spheres settling in a vertical plane due to gravity in Stokes flow has been evaluated numerically for a two-parameter family of initial configurations, with the sphere centers close to each other and located on a horizontal line. A condition has been specified which relates the cluster lifetime to its geometry. The cluster lifetime and the label of the sphere left behind are very sensitive to initial conditions, as within the point-particle approximation of Janosi et al. [Phys. Rev. E 56, 2858 (1997)]. The finding is that an increase of the sphere radii always reduces the range of initial conditions leading to chaotic scattering. The hydrodynamic interactions between close spheres stabilize the cluster.

Keywords:

Stokes flow, particles settling under gravity, hydrodynamic interactions, chaotic scattering, cluster lifetime

Affiliations:
Ekiel-Jeżewska M.L.-IPPT PAN
Wajnryb E.-IPPT PAN
28.Myłyk A., Meile W., Brenn G., Ekiel-Jeżewska M.L., Break-up of suspension drops settling under gravity in a viscous fluid close to a vertical wall, PHYSICS OF FLUIDS, ISSN: 1070-6631, DOI: 10.1063/1.3600660, Vol.23, pp.063302-1-14, 2011
Abstract:

The evolution of suspension drops sedimenting under gravity in a viscous fluid close to a vertical wall was studied experimentally and numerically with the use of the point-force model, in the Stokes flow regime. The fluid inside and outside the drop was identical. The initial distribution of the suspended solid heavy particles was uniform inside a spherical volume. In the experiments and in the simulations, the suspension drops evolved qualitatively in the same way as in an unbounded fluid. However, it was observed, both experimentally and numerically, that, on the average, the destabilization time T and the distance L traveled by the drop until break-up were smaller for a closer distance h of the drop center from the wall, with approximately linear dependence of T and L on D/h, for h larger or comparable to the drop diameter D. Destabilization times and lengths of individual drops with different random configurations of the particles were shown to differ significantly from each other, owing to the chaotic nature of the particle dynamics.

Keywords:

suspension drop, Stokes flow, point-particle model, experiment, destabilization time

Affiliations:
Myłyk A.-IPPT PAN
Meile W.-Graz University of Technology (AT)
Brenn G.-Graz University of Technology (AT)
Ekiel-Jeżewska M.L.-IPPT PAN
29.Cichocki B., Ekiel-Jeżewska M.L., Nägele G., Wajnryb E., First-order virial expansion of short-time diffusion and sedimentation coefficients of permeable particles suspensions, PHYSICS OF FLUIDS, ISSN: 1070-6631, DOI: 10.1063/1.3626196, Vol.23, pp.083303-1-8, 2011
Abstract:

For suspensions of permeable particles, the short-time translational and rotational self-diffusion coefficients, and collective diffusion and sedimentation coefficients are evaluated theoretically. An individual particle is modeled as a uniformly permeable sphere of a given permeability, with the internal solvent flow described by the Debye-Bueche-Brinkman equation. The particles are assumed to interact non-hydrodynamically by their excluded volumes. The virial expansion of the transport properties in powers of the volume fraction is performed up to the two-particle level. The first-order virial coefficients corresponding to two-body hydrodynamic interactions are evaluated with very high accuracy by the series expansion in inverse powers of the inter-particle distance. Results are obtained and discussed for a wide range of the ratio, x, of the particle radius to the hydrodynamic screening length inside a permeable sphere. It is shown that for x≥10, the virial coefficients of the transport properties are well-approximated by the hydrodynamic radius (annulus) model developed by us earlier for the effective viscosity of porous-particle suspensions.

Keywords:

Stokes equations, hydrodynamic interactions, diffusion, sedimentation, permeable particles, suspesnion, virial expansion

Affiliations:
Cichocki B.-University of Warsaw (PL)
Ekiel-Jeżewska M.L.-IPPT PAN
Nägele G.-Forschugszentrum Jülich, Institute of Complex Systems (DE)
Wajnryb E.-IPPT PAN
30.Adamczyk Z., Sadlej K., Wajnryb E., Nattich M., Ekiel-Jeżewska M.L., Bławzdziewicz J., Streaming potential studies of colloidal, polyelectrolyte and protein deposition, ADVANCES IN COLLOID AND INTERFACE SCIENCE, ISSN: 0001-8686, DOI: 10.1016/j.cis.2009.09.004, Vol.153, pp.1-29, 2010
Abstract:

Recent developments in the electrokinetic determination of particle, protein and polyelectrolyte monolayers at solid/electrolyte interfaces, are reviewed. Illustrative theoretical results characterizing particle transport to interfaces are presented, especially analytical formulae for the limiting flux under various deposition regimes and expressions for diffusion coefficients of various particle shapes. Then, blocking effects appearing for higher surface coverage of particles are characterized in terms of the random sequential adsorption model. These theoretical predictions are used for interpretation of experimental results obtained for colloid particles and proteins under convection and diffusion transport conditions. The kinetics of particle deposition and the structure of monolayers are analyzed quantitatively in terms of the generalized random sequential adsorption (RSA) model, considering the coupling of the bulk and surface transport steps. Experimental results are also discussed, showing the dependence of the jamming coverage of monolayers on the ionic strength of particle suspensions. In the next section, theoretical and experimental results pertaining to electrokinetics of particle covered surfaces are presented. Theoretical models are discussed, enabling a quantitative evaluation of the streaming current and the streaming potential as a function of particle coverage and their surface properties (zeta potential). Experimental data related to electrokinetic characteristics of particle monolayers, mostly streaming potential measurements, are presented and interpreted in terms of the above theoretical approaches. These results, obtained for model systems of monodisperse colloid particles are used as reference data for discussion of experiments performed for polyelectrolyte and protein covered surfaces. The utility of the electrokinetic measurements for a precise, in situ determination of particle and protein monolayers at various interfaces is pointed out.

Keywords:

Colloid deposition, Nanoparticle deposition, Particle covered surfaces, Polyelectrolyte deposition, Protein deposition, Streaming potential of covered surfaces

Affiliations:
Adamczyk Z.-Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences (PL)
Sadlej K.-IPPT PAN
Wajnryb E.-IPPT PAN
Nattich M.-Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences (PL)
Ekiel-Jeżewska M.L.-IPPT PAN
Bławzdziewicz J.-Texas Tech University (US)
31.Sadlej K., Wajnryb E., Ekiel-Jeżewska M.L., Lamparska D., Kowalewski T.A., Dynamics of nanofibres conveyed by low Reynolds number flow in a microchannel, INTERNATIONAL JOURNAL OF HEAT AND FLUID FLOW, ISSN: 0142-727X, DOI: 10.1016/j.ijheatfluidflow.2010.02.021, Vol.31, No.6, pp.996-1004, 2010
Abstract:

In this paper we aim to create an experimental and numerical model of nano and micro filaments suspended in a confined Poiseuille flow. The experimental data obtained for short nanofibres will help to elucidate fundamental questions concerning mobility and deformation of biological macromolecules due to hydrodynamic stresses from the surrounding fluid motion. Nanofibres used in the experiments are obtained by electrospinning polymer solutions. Their typical dimensions are 100–1000 μm (length) and 0.1–1 μm (diameter). The nanofibre dynamics is followed experimentally under a fluorescence microscope. A precise multipole expansion method of solving the Stokes equations, and its numerical implementation are used to construct a bead-spring model of a filament moving in a Poiseuille flow between two infinite parallel walls. Simulations show typical behaviour of elongated macromolecules. Depending on the parameters, folding and unfolding sequences of a flexible filament are observed, or a rotational and translation motion of a shape-preserving filament. An important result of our experiments is that nanofibres do not significantly change their shape while interacting with a micro-flow. It appeared that their rotational motion is better reproduced by the shape-preserving Stokesian bead model with all pairs of beads connected by springs, omitting explicit bending forces.

Keywords:

Nanofibres suspension, Microchannels, Filament dynamics, Stokesian dynamics, Multipole expansion

Affiliations:
Sadlej K.-IPPT PAN
Wajnryb E.-IPPT PAN
Ekiel-Jeżewska M.L.-IPPT PAN
Lamparska D.-IPPT PAN
Kowalewski T.A.-IPPT PAN
32.Abade G.C., Cichocki B., Ekiel-Jeżewska M.L., Nägele G., Wajnryb E., Short-time dynamics of permeable particles in concentrated suspensions, JOURNAL OF CHEMICAL PHYSICS, ISSN: 0021-9606, DOI: 10.1063/1.3274663, Vol.132, pp.014503-1-17, 2010
Abstract:

We study short-time diffusion properties of colloidal suspensions of neutral permeable particles. An individual particle is modeled as a solvent-permeable sphere of interaction radius a and uniform permeability k, with the fluid flow inside the particle described by the Debye–Bueche–Brinkman equation, and outside by the Stokes equation. Using a precise multipole method and the corresponding numerical code HYDROMULTIPOLE that account for higher-order hydrodynamic multipole moments, numerical results are presented for the hydrodynamic function, H(q), the short-time self-diffusion coefficient, Ds, the sedimentation coefficient K, the collective diffusion coefficient, Dc, and the principal peak value H(qm), associated with the short-time cage diffusion coefficient, as functions of porosity and volume fraction. Our results cover the full fluid phase regime. Generic features of the permeable sphere model are discussed. An approximate method by Pusey to determine Ds is shown to agree well with our accurate results. It is found that for a given volume fraction, the wavenumber dependence of a reduced hydrodynamic function can be estimated by a single master curve, independent of the particle permeability, given by the hard-sphere model. The reduced form is obtained by an appropriate shift and rescaling of H(q), parametrized by the self-diffusion and sedimentation coefficients. To improve precision, another reduced hydrodynamic function, hm(q), is also constructed, now with the self-diffusion coefficient and the peak value, H(qm), of the hydrodynamic function as the parameters. For wavenumbers qa > 2, this function is permeability independent to an excellent accuracy. The hydrodynamic function of permeable particles is thus well represented in its q-dependence by a permeability-independent master curve, and three coefficients, Ds, K, and H(qm), that do depend on the permeability. The master curve and its coefficients are evaluated as functions of concentration and permeability.

Keywords:

Stokes equations, hydrodynamic interactions, self-diffusion, sedimentation, permeable particles, suspension

Affiliations:
Abade G.C.-Universidade de Brasilia (BR)
Cichocki B.-University of Warsaw (PL)
Ekiel-Jeżewska M.L.-IPPT PAN
Nägele G.-Forschugszentrum Jülich, Institute of Complex Systems (DE)
Wajnryb E.-IPPT PAN
33.Sadlej K., Wajnryb E., Ekiel-Jeżewska M.L., Hydrodynamic interactions suppress deformation of suspension drops in Poiseuille flow, JOURNAL OF CHEMICAL PHYSICS, ISSN: 0021-9606, Vol.133, pp.054901-1-10, 2010
Abstract:

Evolution of a suspensiondrop entrained by Poiseuille flow is studied numerically at a low Reynolds number. A suspensiondrop is modeled by a cloud of many nontouching particles, initially randomly distributed inside a spherical volume of a viscous fluid which is identical to the host fluid outside the drop. Evolution of particle positions and velocities is evaluated by the accurate multipole method corrected for lubrication, implemented in the HYDROMULTIPOLE numerical code. Deformation of the drop is shown to be smaller for a larger volume fraction. At high concentrations, hydrodynamic interactions between close particles significantly decrease elongation of the suspensiondrop along the flow in comparison to the corresponding elongation of the pure-fluid drop. Owing to hydrodynamic interactions, the particles inside a dense-suspension drop tend to stay for a long time together in the central part of the drop; later on, small clusters occasionally separate out from the drop, and are stabilized by quasiperiodic orbits of the constituent nontouching particles. Both effects significantly reduce the drop spreading along the flow. At large volume fractions, suspensiondrops destabilize by fragmentation, and at low volume fractions, by dispersing into single particles.

Keywords:

Stokes equations, Poiseuille flow, suspension drop, hydrodynamic interactions

Affiliations:
Sadlej K.-IPPT PAN
Wajnryb E.-IPPT PAN
Ekiel-Jeżewska M.L.-IPPT PAN
34.Abade G.C., Cichocki B., Ekiel-Jeżewska M.L., Nägele G., Wajnryb E., High-frequency viscosity of concentrated porous particles suspensions, JOURNAL OF CHEMICAL PHYSICS, ISSN: 0021-9606, DOI: 10.1063/1.3474804, Vol.133, pp.084906-1-9, 2010
Abstract:

We determine the high-frequency limiting shear viscosity in colloidal suspensions of rigid, uniformly porous spheres of radius a as a function of volume fraction and inverse porosity parameter x. Our study covers the complete fluid-state regime. The flow inside the spheres is modeled by the Debye–Bueche–Brinkman equation using the boundary condition that fluid velocity and stress change continuously across the sphere surfaces. The many-sphere hydrodynamic interactions in concentrated systems are fully accounted for by a precise hydrodynamic multipole method encoded in our HYDROMULTIPOLE program extended to porous particles. A truncated virial expansion is used to derive an accurate and easy-to-use generalized Saitô formula for. The simulation data are used to test the performance of two simplifying effective particle models. The first model describes the effective particle as a nonporous sphere characterized by a single effective radius dependent on x. In the more refined second model, the porous spheres are modeled as spherical annulus particles with an inner hydrodynamic radius as a function of x, defining the nonporous dry core and characterizing hydrodynamic interactions, and an outer excluded volume radius a characterizing the unchanged direct interactions. Only the second model is in a satisfactory agreement with the simulation data.

Keywords:

Stokes flow, permeable particles, effective viscosity, lubrication, concentrated suspensions

Affiliations:
Abade G.C.-Universidade de Brasilia (BR)
Cichocki B.-University of Warsaw (PL)
Ekiel-Jeżewska M.L.-IPPT PAN
Nägele G.-Forschugszentrum Jülich, Institute of Complex Systems (DE)
Wajnryb E.-IPPT PAN
35.Bławzdziewicz J., Ekiel-Jeżewska M.L., Wajnryb E., Motion of a spherical particle near a planar fluid-fluid interface: The effect of surface incompressibility, JOURNAL OF CHEMICAL PHYSICS, ISSN: 0021-9606, DOI: 10.1063/1.3475197, Vol.133, No.11, pp.114702-1-12, 2010
Abstract:

Hydrodynamic coupling of a spherical particle to an undeformable planar fluid-fluidinterface under creeping-flow conditions is discussed. The interface can be either surfactant-free or covered with an incompressible surfactant monolayer. In the incompressible surfactant limit, a uniform surfactant concentration is maintained by Marangoni stresses associated with infinitesimal surfactant redistribution. Our detailed numerical calculations show that the effect of surface incompressibility on lateral particle motion is accurately accounted for by the first reflection of the flow from the interface. For small particle-interface distances, the remaining contributions are significant, but they are weakly affected by the surface incompressibility. We show that for small particle-wall gaps, the transverse and lateral particle resistance coefficients can be rescaled onto corresponding universal master curves. The scaling functions depend on a scaling variable that combines the particle-wall gap with the viscosity ratio between fluids on both sides of the interface. A logarithmic dependence of the contact value of the lateral resistance function on the viscosity ratio is derived. Accurate numerical calculations are performed using our Cartesian-representation method.

Keywords:

Viscosity, Friction, Lubrication, Liquid liquid interfaces, Surfactants

Affiliations:
Bławzdziewicz J.-Texas Tech University (US)
Ekiel-Jeżewska M.L.-IPPT PAN
Wajnryb E.-IPPT PAN
36.Bławzdziewicz J., Ekiel-Jeżewska M.L., Wajnryb E., Hydrodynamic coupling of spherical particles to a planar fluid-fluid interface: Theoretical analysis, JOURNAL OF CHEMICAL PHYSICS, ISSN: 0021-9606, DOI: 10.1063/1.3475217, Vol.133, pp.114703-1-11, 2010
Abstract:

We have developed a new technique based on our Cartesian-representation method to describe hydrodynamic interactions of a spherical particle with an undeformable planar fluid-fluid interface under creeping-flow conditions. The interface can be either surfactant-free or covered with an incompressible surfactant monolayer. We consider the effect of surface incompressibility and surface viscosity on particle motion. The new algorithm allows to calculate particle mobility coefficients for hydrodynamically coupled particles, moving either on the same or on the opposite sides of the interface.

Keywords:

Stokes equations, hydrodynamic interactions, fluid-fluid interface, surfactant

Affiliations:
Bławzdziewicz J.-Texas Tech University (US)
Ekiel-Jeżewska M.L.-IPPT PAN
Wajnryb E.-IPPT PAN
37.Abade G.C., Cichocki B., Ekiel-Jeżewska M.L., Nägele G., Wajnryb E., High-frequency viscosity and generalized Stokes–Einstein relations in dense suspensions of porous particles, JOURNAL OF PHYSICS-CONDENSED MATTER, ISSN: 0953-8984, DOI: 10.1088/0953-8984/22/32/322101, Vol.22, pp.322101-1-6, 2010
Abstract:

We study the high-frequency limiting shear viscosity, η∞, of colloidal suspensions of uncharged porous particles. An individual particle is modeled as a uniformly porous sphere with the internal solvent flow described by the Debye–Bueche–Brinkman equation. A precise hydrodynamic multipole method with a full account of many-particle hydrodynamic interactions encoded in the HYDROMULTIPOLE program extended to porous particles, is used to calculate η∞ as a function of porosity and concentration. The second-order virial expansion for η∞ is derived, and its range of applicability assessed. The simulation results are used to test the validity of generalized Stokes–Einstein relations between η∞ and various short-time diffusion coefficients, and to quantify the accuracy of a simplifying cell model calculation of η∞. An easy-to-use generalized Saitˆo formula for η∞ is presented which provides a good description of its porosity and concentration dependence.

Keywords:

Stokes flow, hydrodynamic interactions, permeable particles, dense suspensions, effective viscosity

Affiliations:
Abade G.C.-Universidade de Brasilia (BR)
Cichocki B.-University of Warsaw (PL)
Ekiel-Jeżewska M.L.-IPPT PAN
Nägele G.-Forschugszentrum Jülich, Institute of Complex Systems (DE)
Wajnryb E.-IPPT PAN
38.Abade G.C., Cichocki B., Ekiel-Jeżewska M.L., Nägele G., Wajnryb E., Dynamics of permeable particles in concentrated suspensions, PHYSICAL REVIEW E, ISSN: 1539-3755, DOI: 10.1103/PhysRevE.81.020404, Vol.81, pp.020404-1-4, 2010
Abstract:

We calculate short-time diffusion properties of suspensions of porous colloidal particles as a function of their permeability, for the full fluid-phase concentration range. The particles are modeled as spheres of uniform permeability with excluded volume interactions. Using a precise multipole method encoded in the HYDROMULTIPOLE program, results are presented for the hydrodynamic function, H(q), sedimentation coefficient, and self-diffusion coefficients with a full account of many-body hydrodynamic interactions. While self-diffusion and sedimentation are strongly permeability dependent, the wave-number dependence of the hydrodynamic function can be reduced by appropriate shifting and scaling, to a single master curve, independent of permeability. Generic features of the permeable sphere model are discussed.

Keywords:

Stokes equations, hydrodynamic interactions, permeable particles, concentrated suspensions, self-diffusion, hydrodynamic function, collective diffusion

Affiliations:
Abade G.C.-Universidade de Brasilia (BR)
Cichocki B.-University of Warsaw (PL)
Ekiel-Jeżewska M.L.-IPPT PAN
Nägele G.-Forschugszentrum Jülich, Institute of Complex Systems (DE)
Wajnryb E.-IPPT PAN
39.Myłyk A., Ekiel-Jeżewska M.L., How walls influence destabilization of a suspension drop settling under gravity in a viscous fluid?, COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS, ISSN: 0927-7757, DOI: 10.1016/j.colsurfa.2010.01.013, Vol.365, pp.109-111, 2010
Abstract:

An experiment was performed to test the influence of walls on destabilization of a suspension drop settling under gravity in a viscous fluid in the low Reynolds number regime. The averaged distance the drop settled until destabilization was determined. In was found that in the presence of one or two parallel vertical walls close by, the destabilization length is shorter than in an unbounded fluid.

Keywords:

Low Reynolds number flow, Destabilization of suspension drop

Affiliations:
Myłyk A.-IPPT PAN
Ekiel-Jeżewska M.L.-IPPT PAN
40.Adamczyk Z., Sadlej K., Wajnryb E., Ekiel-Jeżewska M.L., Warszyński P., Hydrodynamic radii and diffusion coefficients of particle aggregates derived from the bead model, JOURNAL OF COLLOID AND INTERFACE SCIENCE, ISSN: 0021-9797, DOI: 10.1016/j.jcis.2010.03.066, Vol.347, pp.192-201, 2010
Abstract:

The multiple expansion method was applied for calculating friction tensors and hydrodynamic radii RH of rigid molecules of various shape, composed of ns equal sized, touching spheres. The maximum value of ns studied was 450, which covers most situations met in practice. Calculations were performed for linear chains, half-circles, circles (cyclic molecules) and S-shaped aggregates. It was shown that our results agreed with previous theoretical data obtained for linear chains and cyclic aggregates, for ns < 100. For larger ns, studied exclusively in our work, interpolating analytical expressions were formulated for the hydrodynamic radii RH. These expressions, involving logarithmic function of the aspect ratio parameter (length to width ratio of the macromolecules), are the main finding of our work. Using these expressions, the ratio of the hydrodynamic radius of cyclic-to-linear aggregate qf was calculated, which is a parameter of vital significance. It was determined that qf attained values close to 0.95 for ns ∼450. This suggests that the previous analytical results derived by Tchen [19], in the slender body limit, who predicted that qf → 12/11 = 1.09, are not applicable for ns < 450. Using the RH values, the average translation diffusion coefficients and the sedimentation coefficients for these aggregate shapes were calculated. It was shown that our theoretical results are in good agreement with experimental data obtained for polyelectrolytes and for DNA fragments of various molecular mass. It was concluded that our results can be effectively used to determine the shape of macromolecules, in particular to discriminate between linear and cyclic DNA configurations.

Keywords:

Aggregates of particles of various shapes, Bead model of particle aggregates, Diffusion coefficients of particle aggregates, DNA bead model of, DNA fragment hydrodynamic radii, Hydrodynamic radius of aggregates, Linear chain aggregates, Sedimentation coefficients of aggregates and macromolecules

Affiliations:
Adamczyk Z.-Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences (PL)
Sadlej K.-IPPT PAN
Wajnryb E.-IPPT PAN
Ekiel-Jeżewska M.L.-IPPT PAN
Warszyński P.-other affiliation
41.Cichocki B., Ekiel-Jeżewska M.L., Green tensors for Debye–Büche–Brinkman equations generalized for axisymmetric medium, JOURNAL OF MATHEMATICAL PHYSICS, ISSN: 0022-2488, DOI: 10.1063/1.3498686, Vol.51, pp.103101-1-12, 2010
Abstract:

A fluid flow through a nonisotropic porous medium with an axial symmetry is considered. The Green tensors for the corresponding nonisotropic Debye–Büche–Brinkman equations are calculated in terms of single integrals. Short-distance and far-field limiting behavior is discussed. The exact solution for the Green tensors is found explicitly in the limiting case of an infinite shielding length along the symmetry axis of the system.

Keywords:

Tensor methods, Porous media, Fluid equations, Integral equations, Exact solutions

Affiliations:
Cichocki B.-University of Warsaw (PL)
Ekiel-Jeżewska M.L.-IPPT PAN
42.Feuillebois F., Ekiel-Jeżewska M.L., Suspensions de particules et interactions hydrodynamiques dans fun luide visqueux, Annales / Centre Scientifique de l'Académie Polonaise des Sciences, Vol.12, pp.44-61, 2010
Abstract:

Un groupe polonais (dont les responsables ont été B. Cichocki durant la période 1996-1997 et M. L. Ekiel-Jeżewska depuis 1998 jusqu’à ce jour, en 2010) et un groupe français (dont le responsable est F. Feuillebois) collaborent depuis 1996 dans le cadre des échanges entre le CNRS (Laboratoires PMMH jusqu’à fin 2009, puis maintenant LIMSI) et l’Académie des Sciences de Pologne (IPPT PAN). Le domaine d’étude de cette collaboration en Mécanique des Fluides concerne les suspensions de particules dans des fluides visqueux et en particulier les interactions hydrodynamiques dans les suspensions.

Keywords:

suspensions, hydrodynamic interactions, viscous fluids, microscale

Affiliations:
Feuillebois F.-Laboratoire d'Informatique pour la Mécanique et les Sciences de l'Ingénieur (FR)
Ekiel-Jeżewska M.L.-IPPT PAN
43.Ekiel-Jeżewska M.L., Odnalezione akta Biblioteki Powiatowego Oddziału ZNP w Mińsku Mazowieckim, Rocznik Mińskomazowiecki, ISSN: 1232-633X, Vol.18, pp.124-135, 2010
Abstract:

Na podstawie archiwaliów dotyczących oświaty i życia społecznego w powiecie mińskim odnalezionych w mieszkaniu nauczycieli Janiny i Józefa Sylwestrowiczów opowiedziana zostaje ciekawa historia Biblioteki Oddziału Powiatowego Związku Nauczycielstwa Polskiego w Mińsku Mazowieckim w okresie od lat trzydziestych po pięćdziesiąte. Opowieść ta ilustruje, jak ważną rolę może mieć udostępnienie nowych, nieznanych dotąd i nie opracowanych dokumentów w ramach nowej stałej wystawy w Muzeum Ziemi Mińskiej. Otóż analiza materiałów źródłowych przez młodzież szkolną i pedagogów w ramach warsztatów edukacyjnych wykorzystujących te zbiory może przyczynić się do głębszego poznania historii regionu, a zarazem stworzenia nowych atrakcyjnych form kształcenia.

Keywords:

biblioteka nauczycielska, muzeum, edukacja

Affiliations:
Ekiel-Jeżewska M.L.-IPPT PAN
44.Ekiel-Jeżewska M.L., Zabytkowe kuchnie i łazienki w Mińsku Mazowieckim i Paryżu, Rocznik Mińskomazowiecki, ISSN: 1232-633X, Vol.18, pp.187255-260, 2010
Abstract:

W artykule na fotografiach pokazujemy fragment tworzonej właśnie w Muzeum Ziemi Mińskiej nowej wystawy stałej, a mianowicie skromnie wyposażoną kuchnię i łazienkę polskiego mieszkania nauczycieli w okresie międzywojennym, a obok analogiczne wnętrza stanowiące ekspozycję stałą Muzeum Nissim de Camondo w Paryżu.

Celem tworzonej wystawy stałej jest przedstawienie postaw obywatelskich, działań, dziejów i realiów życia Polaków w I połowie XX wieku, ze szczególnym podkreśleniem roli nauczycieli w budowaniu systemu polskiej państwowości po I wojnie światowej – tworzeniu kultury, samorządności i powszechnej edukacji. Wiodącą koncepcją wystawy jest pokazanie tych procesów na przykładzie jednej rodziny nauczycieli. Pokazanie realiów codzienności - m. in. poprzez wyposażenie kuchni i łazienki - zilustruje typową dla dwudziestolecia międzywojennego oszczędność i funkcjonalność, a ponadto pomoże zwiedzającym poczuć się w tym mieszkaniu jak ,,u siebie'' a dzięki temu ułatwi identyfikację z pokazanymi na wystawie postawami życiowymi i pomoże w zrozumieniu procesów historycznych oraz kontekstu skutcznej edukacji.

Keywords:

edukacja, oszczędność, tradycje i wartości II RP

Affiliations:
Ekiel-Jeżewska M.L.-IPPT PAN
45.Ekiel-Jeżewska M.L., W Muzeum Ziemi Mińskiej ożyją przedwojenne tradycje polskich nauczycieli, Rocznik Mińskomazowiecki, ISSN: 1232-633X, Vol.18, pp.190-196, 261-262, 2010
Abstract:

Wielowątkowa kolekcja oświatowa Sylwestrowiczów jest zalążkiem, który stwarza szansę na pokazanie w Muzeum Ziemi Mińskiej szerokim kręgom zainteresowanych, na czym polegało życie i praca przedwojennych polskich nauczycieli. Na nowej stałej wystawie można tu będzie usłyszeć barwną opowieść, ilustrowaną prawdziwymi rekwizytami tej właśnie rodziny, ich zdjęciami i dokumentami, odwiedzić pokoje, z których ,,jakby przed chwilą wyszli'' dawni mieszkańcy, posłuchać wspomnień z tamtych lat. A studentów i pedagogów z pewnością zaciekawi wzięcie udziału w lekcji szkolnej i poeksperymentowanie zgodnie z treścią podręcznika czy zapisków nauczyciela, a także zapoznanie się na podstawie dokumentacji z przebiegiem kursów pedagogicznych i rolą bibliotek1 oraz przestudiowanie przedwojennych dokumentów.

Keywords:

Nauka, edukacja, muzeum, tradycja, pedagog

Affiliations:
Ekiel-Jeżewska M.L.-IPPT PAN
46.Sadlej K., Wajnryb E., Bławzdziewicz J., Ekiel-Jeżewska M.L., Adamczyk Z., Streaming current and streaming potential for particle covered surfaces: Virial expansion and simulations, JOURNAL OF CHEMICAL PHYSICS, ISSN: 0021-9606, DOI: 10.1063/1.3103545, Vol.130, pp.144706-1-11, 2009
Abstract:

Streaming potential changes induced by deposition of particles at solid/liquid interfaces are considered theoretically. The solution is obtained in terms of a virial expansion of the streaming potential up to the third order of the surface coverage of particles, assumed to be distributed according to the hard sphere equilibrium distribution function. Theoretical methods, including the idea of cluster expansion, are adopted from statistical physics. In the cluster expansion, two-body and three-body hydrodynamic interactions are evaluated with a high precision using the multipole method. The multipole expansion algorithm is also used to perform numerical simulations of the streaming potential, valid for the entire surface coverage range met in practice. Results of our calculations are in good agreement with the experimental data for spherical latex particles adsorbed on a mica surface.

Keywords:

Streaming current, streaming potential, particle-covered wall, Stokes equations, hydrodynamic interactions, multiple expansion, viral exapnsion

Affiliations:
Sadlej K.-IPPT PAN
Wajnryb E.-IPPT PAN
Bławzdziewicz J.-Texas Tech University (US)
Ekiel-Jeżewska M.L.-IPPT PAN
Adamczyk Z.-Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences (PL)
47.Cichocki B., Ekiel-Jeżewska M.L., Self-diffusion of a sphere in an effective medium of rods, JOURNAL OF CHEMICAL PHYSICS, ISSN: 0021-9606, DOI: 10.1063/1.3146786, Vol.130, pp.214902-1-6, 2009
Abstract:

Self-diffusion of a sphere in a network of rods is analyzed theoretically.Hydrodynamic interactions are taken into account according to the model of Dhont et al. [J. Chem. Phys.122, 044905 (2005); Dhont et al., J. Chem. Phys.124, 044907 (2006); Dhont et al., J. Chem. Phys.126, 214501 (2007)] based on the Debye–Bueche–Brinkman equation. The hydrodynamic screening length of the effective medium is assumed to be much larger than the sphere radius and the rod thickness. The self-diffusion coefficient, given by Dhont et al. in terms of four-dimensional integrals, is in this work expressed in terms of a single integral only and therefore evaluated numerically with a high precision. Moreover, simple expressions for the self-diffusion coefficient are derived and shown to be independent of the rod length. They can be useful for experimental verification of the model.

Keywords:

Hydrodynamics, Friction, Hydrological modeling, Self diffusion, Tensor methods

Affiliations:
Cichocki B.-University of Warsaw (PL)
Ekiel-Jeżewska M.L.-IPPT PAN
48.Ekiel-Jeżewska M.L., Wajnryb E., Hydrodynamic orienting of asymmetric microobjects under gravity, JOURNAL OF PHYSICS-CONDENSED MATTER, ISSN: 0953-8984, DOI: 10.1088/0953-8984/21/20/204102, Vol.21, No.20, pp.204102-1-8, 2009
Abstract:

It is shown that non-symmetric microobjects orient while settling under gravity in a viscous fluid. To analyze this process, a simple shape is chosen: a non-deformable 'chain'. The chain consists of two straight arms, made of touching solid spheres. In the absence of external torques, the spheres are free to spin along the arms. The motion of the chain is evaluated by solving the Stokes equations with the use of the multipole method. It is demonstrated that the spinning beads speed up sedimentation by a small amount and increase the orientation rate significantly in comparison to the corresponding rigid chain. It is shown that chains orient towards the V-shaped stable stationary configuration. In contrast, rods and star-shaped microobjects do not rotate. The hydrodynamic orienting is relevant for efficient swimming of non-symmetric microobjects and for sedimenting suspensions.

Keywords:

Stokes flow, hydrodynamic interactions, particles settling under gravity, hydrodynamic orientinfg

Affiliations:
Ekiel-Jeżewska M.L.-IPPT PAN
Wajnryb E.-IPPT PAN
49.Alabrudziński S., Ekiel-Jeżewska M.L., Chehata-Gomez D., Kowalewski T.A., Particle clusters settling under gravity in a viscous fluid, PHYSICS OF FLUIDS, ISSN: 1070-6631, DOI: 10.1063/1.3168615, Vol.21, No.7, pp.73302-1-8, 2009
Abstract:

Clusters made of a small number of close solid spherical particles at a random configuration, sedimenting through a viscous fluid at small Reynolds number, were experimentally investigated at a short-time scale. The cluster settling velocities were measured and shown to be well approximated by the ensemble-averaged formula derived earlier for the uniform distribution of the point particles inside a spherical volume. It was emphasized that the “effective radius” of this volume in general should be smaller than the actual radius of a cluster made of the spheres, and the relation between both radii was determined. The formula was also shown to account well for the gravitational settling of rigid conglomerates, measured and computed elsewhere.

Keywords:

cluster of sendimenting particles, small Reynolds number

Affiliations:
Alabrudziński S.-Warsaw University of Technology (PL)
Ekiel-Jeżewska M.L.-IPPT PAN
Chehata-Gomez D.-CNRS (FR)
Kowalewski T.A.-IPPT PAN
50.Ekiel-Jeżewska M.L., Wajnryb E., Precise multipole method for calculating hydrodynamic interactions between spherical particles in the Stokes flow, Theoretical Methods for Micro Scale Viscous Flows, ISBN: 978-81-7895-400-4, pp.127-172, 2009
Abstract:

An efficient procedure with a controlled high accuracy, the spherical-multipole method, is presented, adequate for evaluating Stokesian dynamics of non-deformable spherical particles suspended in a fluid, or hydrodynamic resistance of moving or motionless systems of such particles under low-Reynolds-number flows. We present a few examples of specific applicatins of this method. In this procedure, the relative motion of particles is corrected for lubrication, to achieve fast convergence with the multipole order of the truncation. The main advantage of this algorithm is that it is possible to perform computations with a very high multipole order of the truncation, controlling the accuracy. Moreover, the method is applicable to systems of various types of the particles in a fluid bounded by one or two parallel flat interfaces.

Keywords:

Stokes equations, hydrodynamic interactions, multipole expansion

Affiliations:
Ekiel-Jeżewska M.L.-IPPT PAN
Wajnryb E.-IPPT PAN
51.Ekiel-Jeżewska M.L., Sadlej K., Wajnryb E., Friction of rodlike particles adsorbed to a planar surface in a shear flow, JOURNAL OF CHEMICAL PHYSICS, ISSN: 0021-9606, DOI: 10.1063/1.2957492, Vol.129, pp.41104-1-4, 2008
Abstract:

A planar hard surface covered with elongated stiff rodlike particles in shear flow is considered in the low-Reynolds-number regime assuming low particle surface coverage. The particles are modeled as straight chains of spherical beads. Multipole expansion of the Stokes equations (the accurate HYDROMULTIPOLE algorithm) is applied to evaluate the hydrodynamic force exerted by the fluid on the rodlike particles, depending on their shape, i.e., on the number of beads and their orientation with respect to the wall and to the ambient shear flow.

Keywords:

Stokes flow, hydrodynamic interactions, rigid rod, solid wall, hydrodynamic friction

Affiliations:
Ekiel-Jeżewska M.L.-IPPT PAN
Sadlej K.-IPPT PAN
Wajnryb E.-IPPT PAN
52.Ekiel-Jeżewska M.L., Wajnryb E., Bławzdziewicz J., Feuillebois F., Lubrication approximation for microparticles moving along parallel walls, JOURNAL OF CHEMICAL PHYSICS, ISSN: 0021-9606, DOI: 10.1063/1.3009251, Vol.129, pp.181102-1-4, 2008
Abstract:

Lubrication expressions for the friction coefficients of a spherical particle moving in a fluid between and along two parallel solid walls are explicitly evaluated in the low-Reynolds-number regime. They are used to determine lubrication expression for the particle free motion under an ambient Poiseuille flow. The range of validity and the accuracy of the lubrication approximation are determined by comparing with the corresponding results of the accurate multipole procedure. The results are applicable for thin, wide, and long microchannels, or quasi-two-dimensional systems.

Keywords:

Lubrication, Friction, Poiseuille flow, Particle velocity, Fluid equations

Affiliations:
Ekiel-Jeżewska M.L.-IPPT PAN
Wajnryb E.-IPPT PAN
Bławzdziewicz J.-Texas Tech University (US)
Feuillebois F.-Laboratoire d'Informatique pour la Mécanique et les Sciences de l'Ingénieur (FR)
53.Ekiel-Jeżewska M.L., Gubiec T., Szymczak P., Stokesian dynamics of close particles, PHYSICS OF FLUIDS, ISSN: 1070-6631, DOI: 10.1063/1.2930881, Vol.20, pp.63102-1-10, 2008
Abstract:

Stokesian dynamics simulations of close particles are reported, taking into account lubrication forces and many-body hydrodynamic interactions between spheres. A periodic trajectory of three particles maintaining a permanent proximity to each other has been found and analyzed. This solution is used as a benchmark to study the accuracy and stability of various numerical integration schemes. In particular, different methods of preventing unphysical overlaps of the particles are considered and potential artifacts discussed.

Keywords:

Kinematics, Renormalization, Surface dynamics, Lubrication, Hydrodynamics

Affiliations:
Ekiel-Jeżewska M.L.-IPPT PAN
Gubiec T.-other affiliation
Szymczak P.-University of Warsaw (PL)
54.Myłyk A., Ekiel-Jeżewska M.L., Odwracalność mikroprzepływów, POSTĘPY FIZYKI, ISSN: 0032-5430, Vol.59, No.6, pp.238-243, 2008
Abstract:

In daily life, at the macroscopic scale, inertia of water flows is commonly experienced and applied. However, for micro-objects moving in water environment, inertia is negligible. That is why sometimes the processes observed at the microscale are in contradiction with our intuition. The examples of such amazing effects can be seen on the famous G.I. Taylor’s movie. The aim of this paper is to analyze the most spectacular of the demonstrations presented there: apparently mixed fluid recovers its initial inhomogeneous structure when the direction of the mixing is reversed.

Keywords:

Lepki płyn, odwracalność mikroprzepływów, bezwładność

Affiliations:
Myłyk A.-IPPT PAN
Ekiel-Jeżewska M.L.-IPPT PAN
55.Alabrudziński S., Kowalewski T.A., Ekiel-Jeżewska M.L., Suchecki W., Metoda pomiaru ruchu malej grupy czastek opadajacej w cieczy, Wybrane zagadnienia przepływów i wymiany ciepła, pp.59-85, 2008
Abstract:

Praca zawiera opis badań zjawiska opadania cząstek kulistych w cieczy o dużej lepkości, a w szczególności wzajemnych oddzaiływań między poszczególnymi, opadającymi razem cząstkami. Opisano stanowisko badawcze, sposób przeprowadzenia pomiarów oraz przedstawiono wybrane wyniki badań.

Keywords:

gliceryna, kilka cząsteki szklanych, eksperyment, trajektorie cząstek, dynamika

Affiliations:
Alabrudziński S.-Warsaw University of Technology (PL)
Kowalewski T.A.-IPPT PAN
Ekiel-Jeżewska M.L.-IPPT PAN
Suchecki W.-other affiliation
56.Cichocki B., Ekiel-Jeżewska M.L., Wajnryb E., Hydrodynamic interactions between spheres in a viscous fluid with a flat free surface or hard wall, JOURNAL OF CHEMICAL PHYSICS, ISSN: 0021-9606, DOI: 10.1063/1.2724815, Vol.126, pp.184704-184707, 2007
Abstract:

Hydrodynamic interactions between spheres immersed in a low-Reynolds-number fluid flow close to a flat free surface or hard wall are investigated. The spheres may have different or equal radii, and may be separated from the boundary or at contact with the free surface. A simple and useful expression is derived for the propagator (Green operator) connecting centers of two spheres. In the derivation, the method of images and the displacement theorems are used. Symmetry of the displacement operators is explicitly shown. The significance of these results in efficient Stokesian and Brownian dynamics simulations is outlined. An example of an application is shown.

Keywords:

Free surface, Hydrodynamics, Friction, Fluid flows, Mirrors

Affiliations:
Cichocki B.-University of Warsaw (PL)
Ekiel-Jeżewska M.L.-IPPT PAN
Wajnryb E.-IPPT PAN
57.Dudyński M.T., Ekiel-Jeżewska M.L., The relativistic Boltzmann equation - mathematical and physical aspects, JOURNAL OF TECHNICAL PHYSICS, ISSN: 0324-8313, Vol.48, No.6, pp.39-47, 2007
Abstract:

Mathematical structure of the linearized Boltzmann equation is outlined. Physical interpretation of the assumed relativistic cross-sections is discussed.

Keywords:

relativistic Boltzmann equation, relativistic cross-section

Affiliations:
Dudyński M.T.-other affiliation
Ekiel-Jeżewska M.L.-IPPT PAN
58.Ekiel-Jeżewska M.L., Wajnryb E., Equilibria for the relative motion of three heavy spheres in Stokes fluid flow, PHYSICAL REVIEW E, ISSN: 1539-3755, DOI: 10.1103/PhysRevE.73.046309, Vol.E 73, pp.46309-0, 2006
Abstract:

Dynamics of three identical solid spheres falling under gravity in low-Reynolds-number fluid flow is investigated. Stationary solutions are found. Their stability is discussed. Phase portraits for two types of symmetric motions are calculated.

Keywords:

Stokes equations, hydrodynamic interactions, particles settling under gravity

Affiliations:
Ekiel-Jeżewska M.L.-IPPT PAN
Wajnryb E.-IPPT PAN
59.Ekiel-Jeżewska M.L., Metzger B., Guazzelli E., Spherical cloud of point particles falling in a viscous fluid, PHYSICS OF FLUIDS, ISSN: 1070-6631, DOI: 10.1063/1.2186692, Vol.18, pp.38104-0, 2006
Abstract:

Statistical mechanics is applied to calculate ensemble-averaged particle and fluid velocity fields of a spherical cloud of point particles sedimenting at a low Reynolds number. The analogy with the fall of a liquid drop in another lighter fluid is discussed.

Keywords:

Fluid drops, Tensor methods, Fluid equations, Hydrodynamics, Reynolds stress modeling

Affiliations:
Ekiel-Jeżewska M.L.-IPPT PAN
Metzger B.-CNRS (FR)
Guazzelli E.-CNRS (FR)
60.Ekiel-Jeżewska M.L., Felderhof B.U., Clusters of particles falling in a viscous fluid with periodic boundary conditions, PHYSICS OF FLUIDS, ISSN: 1070-6631, DOI: 10.1063/1.2396910, Vol.18, pp.121502-0, 2006
Abstract:

Exemplary dynamics of three point particles falling under gravity in Stokes flow with periodic boundary conditions is presented in a movie. Stable and unstable solutions of the equations of Stokesian dynamics are explicitly shown for two initial configurations: equilateral triangles with side lengths close to a critical size.

Keywords:

Kinematics, Suspensions, Boundary value problems, Viscosity, Anisotropy

Affiliations:
Ekiel-Jeżewska M.L.-IPPT PAN
Felderhof B.U.-RWTH Aachen University (DE)
61.Ekiel-Jeżewska M.L., Wajnryb E., Accuracy of the multipole expansion applied to a sphere in a creeping flow parallel to a wall, QUARTERLY JOURNAL OF MECHANICS AND APPLIED MATHEMATICS, ISSN: 0033-5614, DOI: 10.1093/qjmam/hbl016, Vol.59, pp.563-585, 2006
Abstract:

An example system is studied to discuss precision of the multipole expansion, applied to determine forces exerted on particles by a viscous low-Reynolds-number fluid flow. A single sphere in an ambient flow (pure shear, quadratic, and modulated shear) parallel to a close plane wall is considered. Forces and torques exerted by the ambient flow on a motionless sphere are evaluated. Their precision is determined and related to a multipole order of the truncation. Similar analysis is performed for a moving sphere with no ambient flow and for a freely moving sphere. Relative motion of the sphere with respect to the wall gives rise to strong lubrication interactions. It is analysed how these interactions affect accuracy of the pure multipole expansion, and what are the smallest distances where it becomes insufficient. An alternative precise method is applied, in which lubrication expressions are subtracted from the hydrodynamic forces and torques, and the residue is evaluated as a fast-convergent series of inverse powers of the distance between the sphere centre and the wall. The accuracy of this procedure is carefully analysed.

Keywords:

Stokes flow, lubrication, multipole method

Affiliations:
Ekiel-Jeżewska M.L.-IPPT PAN
Wajnryb E.-IPPT PAN
62.Ekiel-Jeżewska M.L., Wajnryb E., Three-particle motion under gravity in Stokes flow: an equilibrium for spheres in contrast to “an end-of-world” for point particles, ARCHIVES OF MECHANICS, ISSN: 0373-2029, Vol.58, No.4-5, pp.489-494, 2006
Abstract:

Evolution of three identical solid spheres falling under gravity in a low-Reynolds number flow is investigated for a symmetric initial configuration. Three spheres aligned horizontally at equal distances evolve towards an equilibrium relative configuration while the point particles collapse onto a single point in a finite time.

Keywords:

Stokes equations, hydrodynamic interactions, particles settling under gravity

Affiliations:
Ekiel-Jeżewska M.L.-IPPT PAN
Wajnryb E.-IPPT PAN
63.Ekiel-Jeżewska M.L., Felderhof B.U., Periodic sedimentation of three particles in periodic boundary conditions, PHYSICS OF FLUIDS, ISSN: 1070-6631, DOI: 10.1063/1.2008827, Vol.17, pp.93102-0, 2005
Abstract:

Solutions of the equations of Stokesian dynamics for point particles are found for periodic boundary conditions with three particles per unit cell of a simple cubic lattice. Two particles per cell move with equal velocity, but three particles per cell usually lead to irregular motion. For a class of initial conditions with special symmetry motions are found that are periodic in time as well as in space. It is shown that there is a range of stability in which the motions are robust under perturbation.

Keywords:

Tensor methods, Boundary value problems, Eigenvalues, Periodic solutions, Equations of motion

Affiliations:
Ekiel-Jeżewska M.L.-IPPT PAN
Felderhof B.U.-RWTH Aachen University (DE)

List of chapters in recent monographs
1.
515
Ekiel-Jeżewska M.L., 100 lat Związku Nauczycielstwa Polskiego na terenie powiatu mińskiego 1916-2016, rozdział: O Powiatowej Bibliotece Nauczycielskiej ZNP w Mińsku Mazowieckim w latach 1931-51, Zarząd Oddziału ZNP w Mińsku Mazowieckim, pp.154-169, 2016
2.
339
Ekiel-Jeżewska M.L., Advances in Science, Technology, Higher Education and Society in the Conceptual Age: STHESCA, rozdział: The system of learning and teaching organized by the Polish Commission of the National Education (1773-94), AHFE Conference in US, pp.31-40, 2014
3.
340
Ekiel-Jeżewska M.L., Human Factors of a Global Society; A system of systems perspective, rozdział: Experimenting with Teaching Contexts, CRC Press Taylor & Francis Group, 6000 Broken Sound Parkway NW, Suite 300, Boca Raton, FL 33487-2742, 79, pp.895-905, 2014
4.
305
Cichocki B., Ekiel-Jeżewska M.L., Naegele G., Wajnryb E., Drops and Bubbles in Contact with Solid Surface, rozdział: Hydrodynamic Interactions Between Solid Particles at a Fluid-Gas Interface, Ferrari M., Liggieri L., Miller R., CRC Press, Leiden, pp.93-104, 2012
5.
375
Ekiel-Jeżewska M.L., Wajnryb E., Theoretical Methods for Micro Scale Viscous Flows, rozdział: Precise multipole method for calculating hydrodynamic interactions between spherical particles in the Stokes flow, Transworld Research Network, François Feuillebois and Antoine Sellier (Eds.), pp.127-172, 2009
6.
241
Alabrudziński S., Ekiel-Jeżewska M.L., Suchecki W., Kowalewski T.A., Wybrane zagadnienia przepływu płynów i wymiany ciepła, rozdział: Metoda pomiaru ruchu malej grupy cząstek opadającej w cieczy, Oficyna Wydawnicza Politechniki Warszawskiej (Warszawa), Suchecki W. (Eds.), pp.59-85, 2008
7.
331
Alabrudziński S., Ekiel-Jeżewska M.L., Kowalewski T.A., Urbaniec K., Wybrane zagadnienia mechaniki w budowie urządzeń technicznych, rozdział: Badania eksperymentalne i interpretacja teoretyczna oddziaływań hydrodynamicznych grupy czastek kulistych opadajacych w lepkiej cieczy, Instytut Inżynierii Materiałowej Politechniki Warszawskiej, pp.7-21, 2008
Editor of monographs
1.
298
Ekiel-Jeżewska M.L., Microparticles in Stokes Flows: Symposium in Honor of François Feuillebois' 65th Birthday, 21-24 August 2011, Warsaw, Poland, JOURNAL OF PHYSICS: CONFERENCE SERIES, 392, 2012, IOP SCIENCE, pp.1-176, 2012

Conference papers
1.Cichocki B., Ekiel-Jeżewska M.L., Wajnryb E., Intrinsic viscosity for Brownian particles of arbitrary shape, Symposium on Microparticles in Stokes Flows in Honor of Francois Feuillebois 65th Birthday, 2011-08-21/08-24, Warszawa (PL), DOI: 10.1088/1742-6596/392/1/012004, Vol.392, pp.012004-1-7, 2012
Abstract:

General expressions for the frequency-dependent Brownian contribution to the intrinsic viscosity of arbitrary-shaped particles have been derived from the Smoluchowski equation.

Keywords:

intrinsic viscosity, Brownian motion, particle of arbitrary shape

Affiliations:
Cichocki B.-University of Warsaw (PL)
Ekiel-Jeżewska M.L.-IPPT PAN
Wajnryb E.-IPPT PAN
2.Sadlej K., Wajnryb E., Ekiel-Jeżewska M.L., Kowalewski T.A., Dynamics of nanofibres conveyed by low Reynolds number flow in a microchannel, ExHFT-7, 7th World Conference on Experimental Heat Transfer, Fluid Mechanics and Thermodynamics, 2009-06-28/07-03, Kraków (PL), pp.237-244, 2009
3.Sadlej K., Ekiel-Jeżewska M.L., Wajnryb E., Hydrodynamic friction of polymer absorbed on a planar surface, ICTAM XXII, 22nd International Congress of Theoretical and Applied Mechanics, 2008-08-25/08-29, Adelaide (AU), 2008
Abstract:

A rigid polymer model consisting of two identical spherical particles, irreversibly adsorbed on a planar channel wall is considered. The linear dimensions of the polymer are assumed to be small enough to validate an expansion of the flow inside the channel to linear terms only. The polymer is therefore effectively immersed in a shearing flow. Total hydrodynamic force acting on the polymer is calculated. The dependence of that force on the polymers orientation is derived taking into account symmetries of the system. Large differences in the force are found for different polymer orientations. Applications of these results are sketched.

Keywords:

Stokes equations, hydrodynamic interactions, hydrodynamic friction, rigid rod, plane wall

Affiliations:
Sadlej K.-IPPT PAN
Ekiel-Jeżewska M.L.-IPPT PAN
Wajnryb E.-IPPT PAN
4.Ekiel-Jeżewska M.L., Periodic orbits of Stokesian dynamics, ICTAM XXII, 22nd International Congress of Theoretical and Applied Mechanics, 2008-08-25/08-29, Adelaide (AU), 2008
Abstract:

A family of periodic in time solutions of the Stokesian dynamics has been found numerically for three identical spherical particles settling under gravity in a vertical plane. The particles stay close to each other and hydrodynamic interaction between their surfaces is essential to detect the oscillations, which have not been found in the point-particle simulations. The periodic orbits are responsible for 'chaotic scattering' of the particles, which come and stay for some time sufficiently close to these orbits before 'escaping'. The existence of such periodic solutions is of fundamental importance for understanding evolution of many-particle systems, and also as a benchmark for testing numerical procedures used to evaluate the Stokesian dynamics.

Keywords:

Stokes equations, hydrodynamic interactions, particles settling under gravity, periodic orbits

Affiliations:
Ekiel-Jeżewska M.L.-IPPT PAN

Conference abstracts
1.Ekiel-Jeżewska M.L., Słowicka A.M., Wajnryb E., Dynamics of flexible fibers in shear flows, Flowing matter, 2016-01-11/01-15, Porto (PT), pp.74-75, 2016
2.Słowicka A.M., Stone H.A., Wajnryb E., Ekiel-Jeżewska M.L., Three modes of the dynamics of flexible fibers in shear flow, ICTAM XXIV, 24th International Congress of Theoretical and Applied Mechanics, 2016-08-21/08-26, Montréal (CA), pp.1142-1143, 2016
Abstract:

Dynamics of a single non-Brownian flexible fiber in shear flow at low Reynolds number is investigated numerically. Initially, the fiber is straight and at the equilibrium. For different initial orientations and values of bending stiffness, three generic scenarios are observed: the fiber tends to: align along the vorticity direction, tumble within the plane perpendicular to vorticity, or perform a periodic motion superposed with translation along the flow.

Keywords:

Stokes equations, flexible fibers, shear flow

Affiliations:
Słowicka A.M.-IPPT PAN
Stone H.A.-Princeton University (US)
Wajnryb E.-IPPT PAN
Ekiel-Jeżewska M.L.-IPPT PAN
3.Farutin A., Piasecki T., Słowicka A.M., Misbah C., Wajnryb E., Ekiel-Jeżewska M.L., Migration of vesicles and flexible fibers in poiseuille flow, ICTAM XXIV, 24th International Congress of Theoretical and Applied Mechanics, 2016-08-21/08-26, Montréal (CA), pp.1344-1345, 2016
Abstract:

Dynamics of flexible fibers and vesicles in unbounded planar Poiseuille flow at the low-Reynolds-number are shown to exhibit similar basic features, when their equilibrium (moderate) aspect ratio is the same and vesicle viscosity contrast is relatively high. The lateral migration and accumulation of these two types of flexible objects are analyzed numerically.

Keywords:

Stokes equations, vesicles, flexible fibers

Affiliations:
Farutin A.-Université Grenoble Alpes (FR)
Piasecki T.-IPPT PAN
Słowicka A.M.-IPPT PAN
Misbah C.-CNRS (FR)
Wajnryb E.-IPPT PAN
Ekiel-Jeżewska M.L.-IPPT PAN
4.Gruca M., Bukowicki M., Ekiel-Jeżewska M., Chaotic Scattering and Periodic Dynamics of Regular Clusters of Particles Sedimenting in a Viscous Fluid, 6th International Symposium on Bifurcations and Instabilities in Fluid Dynamics, 2015-07-15/07-17, Paryż (FR), pp.48, 2015
Abstract:

Dynamics of a cluster of non-Brownian particles falling under gravity in a viscous fluid at low-Reynolds-numer regime has been extensively studied in the literature both for small and large number of particles and oscillating motions have been discovered. In this work we investigate dynamics of clusters of many non-Brownian particles in regular configurations settling under gravity in a viscous fluid. The point particle approximation is applied for the hydrodynamic interactions. We find out that a wide range of regular initial configurations of many particles leads to very long lifetime of the cluster with periodic and quasi-periodic relative motions of particles. We vary the relative distance between the particles and observe how does it affect the dynamics. Several types of periodic and quasi-periodic solutions are discovered. For broad range of initial configurations we show that a slight change of initial conditions has a large influence on the system lifetime – we observe chaotic scattering.

Keywords:

complex fluids, Stokesian dynamics, low-Reynolds-number regime

Affiliations:
Gruca M.-IPPT PAN
Bukowicki M.-IPPT PAN
Ekiel-Jeżewska M.-IPPT PAN
5.Słowicka A.M., Wajnryb E., Ekiel-Jeżewska M.L., Flexible Fibers in Shear Flow, 6th International Symposium on Bifurcations and Instabilities in Fluid Dynamics, 2015-07-15/07-17, Paryż (FR), pp.61, 2015
Abstract:

Modes of the dynamics of flexible fibers in shear flow in a plane perpendicular to vorticity are analyzed numerically.

Dynamics of flexible fibers in shear flow are analyzed numerically for a wide range of the ratios A of the fiber bending force to the hydrodynamic force. The Reynolds number is much smaller that unity, and the Péclet number much greater than one. A fiber is modeled as a chain of solid beads as in Ref. [1]. The centers of the consecutive beads are linked by springs. The equilibrium length of each spring is such that the consecutive beads almost touch each other. The spring constant is large, and the fiber’s length practically does not change with time. At the equilibrium, the fiber is straight. At a deformed configuration, there appear a bending force exerted on each bead, proportional to the bending parameter A. The details of the model and the numerical method can be found in Ref. [2]. Velocities of the beads at given positions are evaluated with the use of the HYDROMULTIPOLE numerical code, based on solving the Stokes equations by the multipole expansion [3]. The time-dependent positions of the beads are determined by the adaptive fourth order Runge-Kutta method.

Initially, the fiber is aligned with the flow, and the springs are at the equilibrium. Owing to symmetry, the centers of all the beads move in the plane perpendicular to the vorticity direction. The fiber end-to-end vector tumbles, in a similar way as a rigid elongated body [4]. While the fiber turns, its shape evolves accordingly, and the center-of-mass oscillates across the flow. A surprisingly rich spectrum of different modes is observed when the value of A is systematically changed, with regular and chaotic trajectories. (For the details, see Ref. [5].)

For some ranges of small and large values of A, the center-of-mass trajectories are periodic with a single tumbling time τ, and there is no migration across the flow. For a certain range of small values of A, evolutions during every second tumbling time are the same, but consecutive tumbling times differ from each other, what leads to regular migrating trajectories of the fiber center-of-mass. For moderate values of A, a chaotic behavior is observed - a large sensitivity of the dynamics to a small change of A, with (typically) many irregular, erratic trajectories or (exceptionally) some regular migrating trajectories. At a moderate value of A, a transition is observed between a ‘straightening out’ mode of more stiff fibers to the coiled mode of more flexible fibers. In the straightening out mode, the fiber significantly changes its shape while tumbling - from almost straight and aligned with the flow to S-shaped. In the coiled mode, the fiber is always compact, it never aligns with the flow.

References
[1] E. Gauger, H. Stark, Numerical study of a microscopic artificial swimmer , Phys. Rev. E 74, 021907 (2006).
[2] A. M. Słowicka, E. Wajnryb, M. L. Ekiel-Jeżewska, Lateral migration of flexible fibers in Poiseuille flow between two parallel planar solid walls , Eur. Phys. J. E 36, 1-12 (2013).
[3] B. Cichocki, M. L. Ekiel-Jeżewska, E. Wajnryb, Lubrication corrections for three-particle contribution to short-time self-diffusion coefficients in colloidal dispersions , J. Chem. Phys. 111, 3265 (1999).
[4] G. Jeffery, The Motion of Ellipsoidal Particles Immersed in a Viscous Fluid , Proc. R. Soc. Lond. A. 102, 161-179 (1922).
[5] A. M. Słowicka, E. Wajnryb, M. L. Ekiel-Jeżewska Dynamics of flexible fibers in shear flow , arXiv [cond-mat.soft] (2015).

Keywords:

Stokes equations, flexible fibers, shear flow

Affiliations:
Słowicka A.M.-IPPT PAN
Wajnryb E.-IPPT PAN
Ekiel-Jeżewska M.L.-IPPT PAN
6.Ekiel-Jeżewska M.L., Bukowicki M., Gruca M., Hydrodynamic repulsion of elastic dumbbells, Bulletin of the American Physical Society, ISSN: 0003-0503, Vol.60, No.21, pp.1, 2015
Abstract:

Dynamics of two identical elastic dumbbells, settling under gravity in a viscous fluid at low Reynolds number are analyzed within the point-particle model. Initially, the dumbbells are vertical, their centers are aligned horizontally, and the springs which connect the dumbbell's beads are at the equilibrium. The motion of the beads is determined numerically with the use of the Runge-Kutta method. After an initial relaxation phase, the system converges to a universal time-dependent solution. The elastic dumbbells tumble while falling, but their relative motion is not periodic (as in case of rigid dumbbells or pairs of separated beads). The elastic constraints break the time-reversal symmetry of the motion. As the result, the horizontal distance between the dumbbells slowly increases - they are hydrodynamically repelled from each other. This effect can be very large even though the elastic forces are always much smaller than gravity. [For the details, see M. Bukowicki, M. Gruca, M. L. Ekiel-Jezewska, J. Fluid Mech. 767, p. 95 (2015).]

The dynamics described above are equivalent to the motion of a single elastic dumbbell under a constant external force which is parallel to a flat free surface. The dumbbell migrates away from the interface and its tumbling time increases.

Keywords:

Stokes equations, dumbbells, point-particle model, hydrodynamic repulsion

Affiliations:
Ekiel-Jeżewska M.L.-IPPT PAN
Bukowicki M.-IPPT PAN
Gruca M.-IPPT PAN
7.Gruca M., Bukowicki M., Ekiel-Jeżewska M., Periodic and quasi-periodic motions of many particles falling under gravity in a viscous fluid, Jülich Soft Matter Days, 2014-11-11/11-14, Jülich (DE), pp.102, 2014
Abstract:

We investigate the dynamics of many particles settling under gravity in a viscous fluid within a Stokes flow regime. We consider two families with a very wide range of regular initial configurations of many point-particles which lead to periodic and quasi-periodic motion. We vary the relative distance between the particles and observe how does it affect the dynamics. We observe the oscillations under some out-of-phase rearrangements of the particles and obtain several types of periodic motions for specified range of initial conditions. We also see a large influence of initial conditions on the cluster lifetime.

Keywords:

complex fluid, low-Reynolds-number regime

Affiliations:
Gruca M.-IPPT PAN
Bukowicki M.-IPPT PAN
Ekiel-Jeżewska M.-IPPT PAN
8.Bukowicki M., Gruca M., Ekiel-Jeżewska M., Dynamics of elastic dumbbells sedimenting in a viscous fluid: oscillations and hydrodynamic repulsion, Jülich Soft Matter Days, 2014-11-11/11-14, Jülich (DE), pp.99, 2014
Abstract:

Periodic motion of several particles falling under gravity in a viscous fluid was theoretically and experimentally observed in a range of systems, including some four-particle configurations or a pair of rigid rods. In addition to its fundamental significance, such a motion is considered as important to understand general features of sedimenting random swarms, and suspensions. In this work, we consider a symmetric system of two elastic fibres, modeled as elastic dumbbells, sedimenting in a vertical plane. We focus on the problem how the elasticity (which breaks time-reversal symmetry of the motion) affects the system's dynamics. The point particle model is used. We observe oscillating, but non-periodic motion of the elastic particles. Independently of the value of the spring constant, the hydrodynamic repulsion appears between the dumbbells. The trajectory shift is slower when k tends to 0 or to infinity – in these limiting cases we recover the periodic dynamics reported in the literature. For a given finite but non-zero spring constant we observe existence of a universal time-dependent trajectory to which the system converge.

Keywords:

Stokesian dynamics, elastic dumbbells, hydrodynamics repulsion

Affiliations:
Bukowicki M.-IPPT PAN
Gruca M.-IPPT PAN
Ekiel-Jeżewska M.-IPPT PAN
9.Słowicka A.M., Wajnryb E., Ekiel-Jeżewska M.L., Migration of flexible fibers entrained by Poiseuille flow in microchannel, ICTAM XXIII, 23rd International Congress of Theoretical and Applied Mechanics, 2012-08-19/08-24, Beijing (CN), pp.1-2, 2012
Abstract:

In this work, we consider a single non-Brownian mobile and flexible fiber immersed in Poiseuille flow in a channel consisting of two parallel infinite walls. The dynamics of the fiber is evaluated numerically from the Stokes equations by a multipole code HYDROMULTIPOLE. Investigating the fiber dynamics we found out that fibers migrate to a critical position across the channel. The distance between the wall and a limiting position depends on the fiber elongation and flexibility. For more stiff fibers the critical position results from the interplay between their tendency to drift away from the channel and the repulsive hydrodynamic interaction with the wall. For less stiff fibers the limiting position is not influenced by the presence of the wall. Differences between the critical position for different fibers can be used in the process of microfibers separation by the flow.

Keywords:

Stokes equations, hydrodynamic interactions, Poiseuille flow, flecible fiber

Affiliations:
Słowicka A.M.-IPPT PAN
Wajnryb E.-IPPT PAN
Ekiel-Jeżewska M.L.-IPPT PAN
10.Ekiel-Jeżewska M.L., Myłyk A., Evolution of suspension drops settling under gravity in a viscous fluid near a vertical wall, ICTAM XXIII, 23rd International Congress of Theoretical and Applied Mechanics, 2012-08-19/08-24, Beijing (CN), pp.1-2, 2012
Abstract:

Using the point-force model, we analyze how evolution of a suspension drop settling under gravity in a viscous fluid is influenced by the presence of a vertical wall near by. In particular, we show that a close drop moves away from the wall while settling along.

Keywords:

Stokes equations, suspension drop, sedimentaiton, vertical wall, point particles, hydrodynamic interactions

Affiliations:
Ekiel-Jeżewska M.L.-IPPT PAN
Myłyk A.-IPPT PAN
11.Słowicka A.M., Wajnryb E., Ekiel-Jeżewska M.L., Migration of microfibers entrained by Poiseuille flow in microchannel, III National Conference of Nano and Micromechanics, 2012-07-04/07-06, Warszawa (PL), pp.71-72, 2012
Keywords:

Stokes equations, Poiseuille flow, flexible fibers, migration

Affiliations:
Słowicka A.M.-IPPT PAN
Wajnryb E.-IPPT PAN
Ekiel-Jeżewska M.L.-IPPT PAN
12.Abade G.C., Cichocki B., Ekiel-Jeżewska M.L., Nagele G., Wajnryb E., Diffusion, sedimentation, and rheology of concentrated suspensions of core-shell particles, III National Conference of Nano and Micromechanics, 2012-07-04/07-06, Warszawa (PL), pp.79-80, 2012
Abstract:

Short-time dynamic properties of concentrated suspensions of colloidal core-shell particles have been recently studied [1] using a precise force multipole method which accounts for many-particle hydrodynamic interactions (HIs). A core-shell particle is composed of a rigid, spherical dry core of radius a surrounded by an uniformly permeable shell of outer radius b and hydrodynamic penetration depth κ-1. The solvent flow inside the permeable shell is described by the Brinkman-Debye-Bueche equation, and outside the particles by the Stokes equation. The particles are assumed to interact non-hydrodynamically by a hard-sphere no-overlap potential of radius b. Numerical results are presented for the high-frequency shear viscosity, sedimentation coefficient and the short-time translational and rotational self-diffusion coefficients. The simulation results cover the full three-parametric fluid-phase space of the composite particle model, with the volume fraction extending up to 0.45, and the whole range of values for κb, and a/b. Many-particle hydrodynamic interaction effects on the transport properties are explored, and the hydrodynamic influence of the core in concentrated systems is discussed.

Keywords:

Stokes equations, Brinkman-Debye-Bueche equations, permeable particles, translational and rotational self-diffusion, sedimentation, effective viscosity

Affiliations:
Abade G.C.-Universidade de Brasilia (BR)
Cichocki B.-University of Warsaw (PL)
Ekiel-Jeżewska M.L.-IPPT PAN
Nagele G.-other affiliation
Wajnryb E.-IPPT PAN
13.Myłyk A., Ekiel-Jeżewska M.L., Dynamika układów wielocząstkowych opadających grawitacyjnie w lepkim płynie w pobliżu płaskiej pionowej ściany, III National Conference of Nano and Micromechanics, 2012-07-04/07-06, Warszawa (PL), pp.87, 2012
Abstract:

W niniejszej prezentacji zostanie pokazany wpływ płaskiej pionowej ściany na ewolucję kropli zawiesiny opadającej pod wpływem siły grawitacyjnej w lepkim płynie dla liczb Reynoldsa znacznie mniejszych od jedności. Płyn wewnątrz i na zewnątrz opadającej kropli był identyczny, a cząstki początkowo były przypadkowo rozmieszczone wewnątrz sferycznej objętości. Przeanalizowana zostanie ewolucja opadającej kropli złożonej z cząstek. Krople podczas opadania ,,gubiły'' cząstki, które jako wolniejsze pozostawały z tyłu, tworząc ponad kroplą ,,ogon'', powoli się spłaszczały i rozszerzały, a potem nagle dzieliły na dwa lub więcej fragmentów. Średnia odległość przebyta przez opadającą kroplę zawiesiny aż do rozpadu jest tym któtsza, im mniejsza jest odległość h od środka ściainy. Badanie ewolucji kropli wykonane zostało za pomocą modelu cząstek punktowych w oparciu o funkcje Greena dla równań Stokesa.

Keywords:

liczba Reynoldsa, model cząstek punktowych, równania Stokesa

Affiliations:
Myłyk A.-IPPT PAN
Ekiel-Jeżewska M.L.-IPPT PAN