Sławomir Błoński, Ph.D., Eng.

Department of Biosystems and Soft Matter (ZBiMM)
Division of Modelling in Biology and Medicine (PMBM)
Bio and Micro Fluidics Laboratory
position: specialist
telephone: (+48) 22 826 12 81 ext.: 413
room: 312
e-mail: sblonski
personal site: http://pmbm.ippt.pan.pl/web/Sławomir_Błoński

Doctoral thesis
2009-09-24Analiza przepływu turbulentnego w mikrokanale 
supervisor -- Prof. Tomasz Kowalewski, Ph.D., Dr. Habil., IPPT PAN
622
 
Recent publications
1.Jarecki L., Błoński S., Zachara A., Modeling of Pneumatic Melt Drawing of Poly‑L‑lactide Fibers in the Laval Nozzle, Industrial and Engineering Chemistry Research, ISSN: 0888-5885, DOI: 10.1021/acs.iecr.5b02375, Vol.54, pp.10796-10810, 2015
Abstract:

An air-drawing model of poly-l-lactide melt under a supersonic air jet in the Laval nozzle is presented. The aerodynamic fields are computed using the k–ω model. The pneumatic process is considered based on the mathematical model of melt spinning in single-, thin-filament approximation. Simultaneous acceleration of the air and the melt within the nozzle leads to fast attenuation of the filament. Air velocity dominates velocity of the filament and results in continual air-drawing on the entire spinning line. Oriented crystallization and nonlinear viscoelasticity effects under fast uniaxial elongation of the polymer melt are considered. The filament velocity at the collector increases significantly with increasing air compression, from the values typical for high-speed melt spinning up to values by two folds higher. The increase in filament velocity is limited by the effects of online oriented crystallization at higher air compressions. Influence of the inlet air compression, melt extrusion temperature and weight-average molecular weight on the axial profiles of the melt spinning functions is discussed, as well as on the development of amorphous orientation and online oriented crystallization.

Keywords:

Laval nozzle, Pneumatic melt spinning, Super-thin fibers, Oriented crystallization, Computer simulation, Polylactides

Affiliations:
Jarecki L.-IPPT PAN
Błoński S.-IPPT PAN
Zachara A.-other affiliation
2.Blim A., Jarecki L., Błoński S., Modeling of pneumatic melt drawing of polypropylene super-thin fibers in the Laval nozzle, BULLETIN OF THE POLISH ACADEMY OF SCIENCES: TECHNICAL SCIENCES, ISSN: 0239-7528, DOI: 10.2478/bpasts-2014-0005, Vol.62, No.1, pp.43-54, 2014
Abstract:

Melt spinning of the fibers by supersonic air jet in the Laval nozzle is a novel, efficient and energy saving method of formation of super-thin fibers. In the process, polymer melt is extruded from a row of orifices and fast drawn by the pneumatic forces. In the modelling, air velocity, temperature and pressure distributions are computed from the k-! aerodynamic model. Computations of the polymer air-drawing dynamics are based on the mathematical model of melt spinning in a single-, thin-filament approximation and Phan-Thien/Tanner non-linear viscoelasticity of the polymer melt. Axial profiles of the polymer velocity, temperature, tensile stress and rheological extra-pressure are computed. Influence of the Laval nozzle geometry, initial air compression, an initial melt temperature, a polymer mass output and the diameter of the melt extrusion die is discussed. The role of the polymer molecular weight, melt viscosity and relaxation time is considered. Example computations show the influence of important processing and material parameters. In the supersonic process, a high negative internal extra-pressure is predicted in the polymer melt under high elongation rates which may lead to cavitation and longitudinal burst splitting of the filament into a high number of sub-filaments. A hypothetical number of sub-filaments at the splitting is estimated from an energetic criterion. The diameter of the sub-filaments may reach the range of nano-fibers. A substantial influence of the Laval nozzle geometry is also predicted.

Keywords:

air-drawing, Laval nozzle, pneumatic melt spinning, superthin fibers

Affiliations:
Blim A.-IPPT PAN
Jarecki L.-IPPT PAN
Błoński S.-IPPT PAN
3.Węgrzyn J., Samborski A., Reissig L., Korczyk P.M., Błoński S., Garstecki P., Microfluidic architectures for efficient generation of chemistry gradations in droplets, MICROFLUIDICS AND NANOFLUIDICS, ISSN: 1613-4982, DOI: 10.1007/s10404-012-1042-3, Vol.14, No.1, pp.235-245, 2013
Abstract:

We demonstrate a strategy for construction of high-throughput microfluidic systems generating gradations of chemistry in micro-droplets. The productivity of the systems that we propose is limited only by the maximum rate of the droplet formation, and does not need to be limited by the rate of mixing. Multilayer polycarbonate chips transform two miscible input streams A and B into N streams of droplets, containing mixtures [A]i, [B]i. Exemplary devices generate linear ([B]i ∝ i) and logarithmic gradations (ln[B]i ∝ i). We also analyze the use of the same strategy for the generation of concentration gradation in the streams of droplets comprising mixtures of liquids of different viscosities. The devices preserve the required distribution of compositions, while allowing the volume of the droplets to be tuned over almost two orders of magnitude (i.e. between 3 and 80 nL).

Keywords:

Microfluidics, Generation of gradients, Droplet, Viscosity

Affiliations:
Węgrzyn J.-other affiliation
Samborski A.-other affiliation
Reissig L.-Nagoya University (JP)
Korczyk P.M.-IPPT PAN
Błoński S.-IPPT PAN
Garstecki P.-Institute of Physical Chemistry, Polish Academy of Sciences (PL)
4.Jarecki L., Błoński S., Blim A., Zachara A., Modeling of pneumatic melt spinning processes, JOURNAL OF APPLIED POLYMER SCIENCE, ISSN: 0021-8995, DOI: 10.1002/app.36575, Vol.125, No.6, pp.4402-4415, 2012
Abstract:

Computer simulation of the pneumatic processes of fiber formation from the polymer melts is discussed. The dynamics of air-drawing of thin polymer streams in supersonic air jets formed in the Laval nozzle is presented versus the melt blowing process. In the Laval nozzle process, the air flow takes place with high Reynolds number and the k–omega model is used which considers kinetic energy of the air flow and the specific dissipation rate of the kinetic energy. For melt blowing, the air fields are simulated with the use of the k–epsilon turbulent model. The air velocity, temperature, and pressure distributions along the centerline of the air jets are considered in the modeling of both pneumatic processes. The air fields are predetermined at the absence of the polymer streams for several air compression values in the Laval nozzle inlet and several initial air velocities in the melt blowing process. Each polymer stream in a usual configuration of a single row of the filaments in the process is considered as non-interacting aerodynamically with other streams, and the air jet is assumed to be undisturbed by the polymer streams. Airdrawing of the polymer filaments is simulated as controlled by the distribution of air velocity, temperature, and pressure on the air jet centerline with the use of a stationary model of melt spinning in a single-, thin-filament approximation. Effects of non-linear viscoelasticity of the polymer melt subjected to fast uniaxial elongation are accounted for in the modeling. Strong influence of the air jet velocity, the melt viscosity which controls response of the polymer melt on the air-drawing forces, and the dieto-collector distance has been predicted. Influence of initial air temperature, geometry of the air die, initial velocity and temperature of the melt, extrusion orifice diameter can be also predicted from the model. The example computations concern air-drawing of isotactic polypropylene with the use of the Laval nozzle are compared with the predictions for the melt blowing process.

Keywords:

computer modeling, fibers, melt blowing, supersonic melt spinning, polypropylene

Affiliations:
Jarecki L.-IPPT PAN
Błoński S.-IPPT PAN
Blim A.-IPPT PAN
Zachara A.-other affiliation
5.Błoński S., Domagalski P., Dziubiński M., Kowalewski T.A., Hydro-dynamically modified seeding for micro-PIV, ARCHIVES OF MECHANICS, ISSN: 0373-2029, Vol.63, No.2, pp.163-182, 2011
Abstract:

This paper presents numerical and experimental analysis of the hydrodynamic flow focusing in a rectangular microchannel. Aim of the study is to improve performance of the Particle Image Velocimetry (PIV) technique app lied to micro-scale flow analysis. The symmetric flow focusing system of two channels crossed at right angle is investigated. The numerical model is used to analyse the e ffect of Reynolds number on the flow focusing mechanism. In the experiment, the flow foc using is applied to concentrate seeding tracers into a thin sheet at the channel axis. Such a modification removes the out of focus images of the seeding particles, effe ctively improving PIV evaluation of vector fields in microchannel. Based on the exp erimental and numerical results we have found that expected improvement is possible for the flow at Reynolds number less than 10 only.

Keywords:

selective seeding, flow focusing

Affiliations:
Błoński S.-IPPT PAN
Domagalski P.-other affiliation
Dziubiński M.-other affiliation
Kowalewski T.A.-IPPT PAN
6.Szumbarski J., Błoński S., Destabilization of laminar flow in a rectangular channel by transversely-oriented wall corrugation, ARCHIVES OF MECHANICS, ISSN: 0373-2029, Vol.4, No.63, pp.393-428, 2011
Abstract:

Linear stability of the flow through the transversely corrugated channel with flat sidewalls is investigated numerically. Two variants of the wall corrugation are considered: symmetric sinusoidal waviness of the top and bottom walls and onesided corrugation, i.e., one of the walls remains flat. Spectrally accurate Galerkin method formulated in a transformed domain is used for the solution of the main flow and linear stability equations. Unstable normal modes have been identified and their parametric variation has been determined. The results show that for sufficiently large aspect ratios, the influence of the sidewalls is weak and the stability properties resemble those of the spanwise-periodic channel (investigated recently by the first author). It means that an appropriately designed transversal corrugation may be regarded as a promising method for passive enhancement of mixing in laminar regime.

Keywords:

hydrodynamic stability, wavy channel, wall corrugation, laminar mixing

Affiliations:
Szumbarski J.-other affiliation
Błoński S.-IPPT PAN
7.Jarecki L., Błoński S., Zachara A., Blim A., Computer modeling of pneumatic formation of superthin fibres, COMPUTER METHODS IN MATERIALS SCIENCE / INFORMATYKA W TECHNOLOGII MATERIAŁÓW, ISSN: 1641-8581, Vol.11, No.1, pp.74-80, 2011
Abstract:

Dynamics of a novel pneumatic process of superthin fibres formation from polymer melts in supersonic air jets in the Laval nozzle is studied using computer simulation. The approach bases on the mathematical k-w models of air flow in the nozzle and air drawing of polymer filaments in the coaxial air jet. The aerodynamic fields can be considered as undisturbed by presence of a single row of thin polymer filaments and predetermined air conditions are used in the modeling. The air fields are simulated for several values of the air compressions in the nozzle inlet and two nozzle geometries. Driving force of the Laval nozzle process results form air drag forces acting onto the filament surface. Mathematical model of stationary melt spinning in single-, thin-filament approximation is applied with the effects of non-linear viscoelasticity of the polymer melt accounted for. The model allows also to discuss non-linear stress-optical relationship reflecting online molecular orientation, as well as online crystallization of the polymer filament if it occurs. Negative rheological extra-pressure in the air-drawn filament is predicted, as resulting from non-linear viscoelasticity of the polymer melt subjected to high elongation rates. The negative extra-pressure could lead to cavitation and longitudinal burst splitting of each filament into a high number of superthin sub-filaments. A hypothetical mean diameter of the sub-filaments is estimated from an energetic criterion. Example computations of the dynamic profiles of air drawing and discussion concern isotactic polypropylene (iPP) subjected to the Laval nozzle process.

Keywords:

melt spinning, polymer air drawing, Laval nozzle process, superthin fibres

Affiliations:
Jarecki L.-IPPT PAN
Błoński S.-IPPT PAN
Zachara A.-other affiliation
Blim A.-IPPT PAN
8.Szumbarski J., Błoński S., Kowalewski T.A., Impact of transversely-oriented wall corrugation on hydraulic resistance of a channel flow, Archive of Mechanical Engineering, ISSN: 0004-0738, Vol.LVIII, No.4, pp.441-466, 2011
Abstract:

The impact of the transversely-oriented sinusoidal wall corrugation on the hydraulic drag is investigated numerically for the flow through the channel of finite width and with flat sidewalls. The numerical method, based on the domain transformation and Chebyshev-Galerkin discretization, is used to investigate the flow resistance of the laminar, parallel and pressure-driven flow. The obtained results are compared to the reference case, i.e., to the flow through the channel with rectangular cross section of the same aspect ratio. Simple explanation of the gain in the volumetric flow rate observed in the flow through spanwise-periodic channel with long-wave transversely-oriented wall corrugation is provided. In the further analysis, pressure drop in the flows with larger Reynolds numbers are studied numerically by means of the finite-volume commercial package Fluent. Preliminary experimental results confirm the predicted tendency.

Keywords:

Drug reduction, finite volume flow modeling, corrugated walls

Affiliations:
Szumbarski J.-other affiliation
Błoński S.-IPPT PAN
Kowalewski T.A.-IPPT PAN
9.Bretcanu O., Misra S.K., Yunos D.M., Boccaccini A.R., Roy I., Kowalczyk T., Błoński S., Kowalewski T.A., Electrospun nanofibrous biodegradable polyester coatings on Bioglass®-based glass-ceramics for tissue engineering, MATERIALS CHEMISTRY AND PHYSICS, ISSN: 0254-0584, DOI: 10.1016/j.matchemphys.2009.08.011, Vol.118, pp.420-426, 2009
Abstract:

Biodegradable polymeric nanofibrous coatings were obtained by electrospinning different polymers onto sintered 45S5 Bioglass®-based glass-ceramic pellets. The investigated polymers were poly(3-hydroxybutyrate) (P3HB), poly(3-hydroxybutyrate-co-hydroxyvalerate) (PHBV) and a composite of poly(caprolactone) (PCL) and poly(ethylene oxide) (PEO) (PCL–PEO). The fibrous coatings morphology was evaluated by optical microscopy and scanning electron microscopy. The electrospinning process parameters were optimised to obtain reproducible coatings formed by a thin web of polymer nanofibres. In-vitro studies in simulated body fluid (SBF) were performed to investigate the bioactivity and mineralisation of the substrates by inducing the formation of hydroxyapatite (HA) on the nanofiber-coated pellets. HA crystals were detected on all samples after 7 days of immersion in SBF, however the morphology of the HA layer depended on the characteristic fibre diameter, which in turn was a function of the specific polymer-solvent system used. The bioactive and resorbable nanofibrous coatings can be used to tailor the surface topography of bioactive glass-ceramics for applications in tissue engineering scaffolds.

Keywords:

Electrospinning, Nanofibers, Bioglass®, Polyhydroxyalkanoates, Tissue engineering

Affiliations:
Bretcanu O.-other affiliation
Misra S.K.-other affiliation
Yunos D.M.-other affiliation
Boccaccini A.R.-other affiliation
Roy I.-other affiliation
Kowalczyk T.-IPPT PAN
Błoński S.-IPPT PAN
Kowalewski T.A.-IPPT PAN
10.Błoński S., Analiza przejscia laminarno-turbulentnego w mikrokanalach, IPPT REPORTS, ISSN: 2299-3657, Vol.2, 2009
11.Licznar P., Lomotowski J., Błoński S., Ciach G.J., Microprocessor field impactometer calibration: do we measure drops momentum or their kinetic energy?, JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY, ISSN: 0739-0572, DOI: 10.1175/2007JTECHA938.1, Vol.25, pp.742-753, 2008
Abstract:

This study presents the construction and calibration of a low-cost piezoelectric microprocessor impactometer designed for the field measurements of the rainfall kinetic energy (KE) flux. Its precise calibration was performed in laboratory conditions using waterdrops of different sizes and fall velocities. High-speed photography was applied to measure the velocity of each waterdrop. Although the impactometer constructed for this study is not able to measure the momentum of waterdrops, its accuracy for measuring their KE is excellent. It was found that the processing of the piezoelectric signal might determine which physical quantity is measured by different impactometers. It was also found that the distance between the waterdrop impact position and the impactometer center has a significant effect on the sensor output. A scheme to account for this effect is developed in this study, and the calibration curve for field applications of the impactometer is derived. In addition, an example comparison of the concurrent field measurements of KE flux using the impactometer and rainfall rates using a weighing rain gauge is given.

Keywords:

Rainfall, Dropsize distribution, Kinetic energy

Affiliations:
Licznar P.-other affiliation
Lomotowski J.-other affiliation
Błoński S.-IPPT PAN
Ciach G.J.-other affiliation
12.Kowalewski T.A., Błoński S., Korczyk P., Eksperymentalna analiza przeplywów w skali mikro i nano, Wybrane zagadnienia przepływów i wymiany ciepła, Vol.6, pp.127-149, 2008
Keywords:

mikroprzepływy, eksperymentalna mechanika płynów

Affiliations:
Kowalewski T.A.-IPPT PAN
Błoński S.-IPPT PAN
Korczyk P.-IPPT PAN
13.Błoński S., Korczyk P., Kowalewski T.A., Analysis of turbulence in a micro-channel emulsifier, INTERNATIONAL JOURNAL OF THERMAL SCIENCES, ISSN: 1290-0729, DOI: 10.1016/j.ijthermalsci.2007.01.028, Vol.46, pp.1123-1141, 2007
Abstract:

Turbulent flow of water in an 1 mm long and 0.4 mm high gap of an emulsifier is investigated experimentally using micro-PIV technique and compared with numerical predictions. The purpose of the investigations is to develop a procedure for well-controlled generation of mono-disperse suspension of micro-droplets. The micro-flow measurements are based on epi-fluorescence illumination and high-speed imaging. The experimental data are compared with the numerical results obtained using direct simulation and turbulent flow model. From the turbulent modelling (k−ε) was found that, the maximum of turbulent energy dissipation rate takes place mainly in the micro-channel gap. However, measured and directly simulated (DNS) velocity fields indicate that flow turbulization is delayed and develops shortly behind the gap. Experimental and numerical results are used to predict droplet dimension of two different oil emulsions. Very low amount of oil-phase fraction in investigated emulsions justifies us to use flow characteristics evaluated for pure water to predict mean diameter of oil droplets. These predictions are validated using experimental data on statistics of droplets size.

Keywords:

Micro-flow, Micro-PIV, Particle Image Velocimetry, Turbulence, Micro-channel, Emulsion

Affiliations:
Błoński S.-IPPT PAN
Korczyk P.-IPPT PAN
Kowalewski T.A.-IPPT PAN
14.Błoński S., Kowalewski T.A., PIV analysis of turbulent flow in a micro-channel, JOURNAL OF THEORETICAL AND APPLIED MECHANICS, ISSN: 1429-2955, Vol.45, pp.489-503, 2007
Abstract:

Turbulent flow of water in a short 0.4 mm high micro-channel of an emulsifier is investigated experimentally using a micro-PIV technique and compared with numerical predictions. The micro-flow measurements are based on epi-fluorescence illumination and high-speed imaging. Velocity fields obtained from the measurements and direct numerical simulations indicate that flow turbulization is delayed and develops only at the outlet region of the micro-channe

Keywords:

micro-channel, micro-PIV, turbulence

Affiliations:
Błoński S.-IPPT PAN
Kowalewski T.A.-IPPT PAN
15.Sielamowicz I., Błoński S., Kowalewski T.A., Digital Particle Image Velocimetry (DPIV) technique in measurements of granular material flows, Part 2 of 3 - converging hoppers, CHEMICAL ENGINEERING SCIENCE, ISSN: 0009-2509, Vol.61, pp.5307-5317, 2006
Abstract:

The flow evolution of an amaranth seed is being investigated in a wedge-shaped model made of Plexiglas. The objective of this paper is to recognise flow patterns in the flowing material, and also to depict evolution of velocity fields, flow field discontinuities, velocity profiles for cross-sections of the model, shear zones and flow streamlines using the digital particle image velocimetry (DPIV) optical technique. It is demonstrated that the DPIV technique used in the experiments enables quantitative analysis of the flow zones geometry. The technique also allows to reveal boundaries between flowing and stagnant zones and to extract velocity profiles at any selected sections of the model.

Keywords:

Optical technique, DPIV, Granular material flows, Converging hopper, Particle, Plug flow, Shear zones, Discharge flow rate

Affiliations:
Sielamowicz I.-University of Zielona Góra (PL)
Błoński S.-IPPT PAN
Kowalewski T.A.-IPPT PAN
16.Sielamowicz I., Kowalewski T.A., Błoński S., Optical technique DPIV in measurements of granular material flows, Part 1/3 - plane hoppers, CHEMICAL ENGINEERING SCIENCE, ISSN: 0009-2509, DOI: 10.1016/j.ces.2004.07.135, Vol.60, pp.589-598, 2005
Abstract:

The aim of this paper is to present the evolution of plug flow developing in three densely packed granular materials in the model of a hopper made of Plexiglas. For this purpose, the digital particle image velocimetry (DPIV) technique is applied to analyse the flow field of the granular material. When discharge starts, a plug flow zone in the flowing material expands upward. This zone changes its width reaching the upper surface of the material. The plug flow evolution as a function of time is described using DPIV. This technique yields the velocity profiles of flowing granular materials, velocity magnitude contours, vector fields, velocity distributions on certain levels in the model and traces of the selected particles. The results obtained for the evolution of the vertical velocity, height and width of the plug flow zone as a function of time, measured at the symmetry axis of the model for the amarantus seed are compared to the results obtained by Waters and Drescher. Measurements of the stagnant boundary as a function of time are compared to the results available in the literature

Keywords:

Optical technique, Experiments, Granular, Materials, Flow, Particle, Plug flow

Affiliations:
Sielamowicz I.-University of Zielona Góra (PL)
Kowalewski T.A.-IPPT PAN
Błoński S.-IPPT PAN
17.Kowalewski T.A., Błoński S., Barral S., Experiments and modelling of electrospinning process, BULLETIN OF THE POLISH ACADEMY OF SCIENCES: TECHNICAL SCIENCES, ISSN: 0239-7528, Vol.53, No.4, pp.385-394, 2005
Abstract:

Very thin liquid jets can be obtained using electric field, whereas an electrically-driven bending instability occurs that enormously increases the jet path and effectively leads to its thinning by very large ratios, enabling the production of nanometre size fibres. This mechanism, although it was discovered almost one century ago, is not yet fully understood. In the following study, experimental data are collected, with the dual goal of characterizing the electro-spinning of different liquids and evaluating the pertinence of a theoretical model.

Keywords:

nanofibres, electrospinning, polymer fibres, electrified liquid jet

Affiliations:
Kowalewski T.A.-IPPT PAN
Błoński S.-IPPT PAN
Barral S.-IPPT PAN

List of recent monographs
1.
85
Błoński S., Analiza przejścia laminarno-turbulentnego w mikrokanałach, IPPT Reports on Fundamental Technological Research, 2, pp.1-154, 2009
List of chapters in recent monographs
1.
184
Kowalewski T.A., Błoński S., Proceedings of 7th World Conference on Experimental Heat Transfer, Fluid mechanics and thermodynamics, Krakow, Poland, 28 June 03 July 2009, rozdział: Turbulence in micro-channels, AGH, Szmyd J.S., Spalek J., Kowalewski T.A. (Eds.), CD-ROM, pp.361-368, 2009
2.
240
Kowalewski T.A., Błoński S., Korczyk P., Wybrane zagadnienia przepływu płynów i wymiany ciepła, rozdział: Eksperymentalna analiza przepływów w skali mikro i nano, Oficyna Wydawnicza Politechniki Warszawskiej (Warszawa), Suchecki W. (Eds.), pp.127-149, 2008

Conference papers
1.Zembrzycki K., Błoński S., Kowalewski T.A., Analysis of wall effect on the process of diffusion of nanoparticles in a microchannel, JOURNAL OF PHYSICS: CONFERENCE SERIES, ISSN: 1742-6588, DOI: 10.1088/1742-6596/392/1/012014, Vol.392, pp.012014-1-11, 2012
Abstract:

In this preliminary work we introduce a new method for verification of the no-slip boundary condition on the liquid-solid interface, by analyzing variations in Brownian motion coefficients of colloidal nanoparticles as a function of distance from the wall. The experimental investigations are performed in a small channel using an epi-fluorescent microscope. For precise measurements close to the wall an evanescent wave illumination is used. The experimental data obtained for 300nm particles gave us evidence of relatively large (0.3μm) slip length. The experiments are supplemented by two-dimensional Molecular Dynamics simulations.

Affiliations:
Zembrzycki K.-IPPT PAN
Błoński S.-IPPT PAN
Kowalewski T.A.-IPPT PAN
2.Malinowski S.P., Górska A., Kowalewski T.A., Korczyk P., Błoński S., Kumala W., Small-scale mixing at cloud top observed in a laboratory cloud chamber - preliminary results, 13th AMS Conference on Cloud Physics, 2010-06-28/07-02, Portland (US), Vol.P1.22, pp.1-4, 2010
Keywords:

small-scale turbulence, cloud, cloud droplets, evaporation

Affiliations:
Malinowski S.P.-other affiliation
Górska A.-other affiliation
Kowalewski T.A.-IPPT PAN
Korczyk P.-IPPT PAN
Błoński S.-IPPT PAN
Kumala W.-University of Warsaw (PL)
3.Błoński S., Domagalski P., Kowalewski T.A., Flow focusing in microfluidic devices, XIX Krajowa Konferencja Mechaniki Płynów, 2010-09-05/09-09, Poznań (PL), Vol.S3/F, pp.1-5, 2010
Abstract:

This paper presents numerical analysis of the hydrodynamic flow focusing in rectangular microchannels. The low Reynolds numer pressure driven flow in symmetric system of crossed channels with three inlets and one outlet is investigated. The numerical model is used to elucidate the origin of broadening of the focused flow sheet observed experimentally close to the side walls of the outlet channel. It is found that the observed broadening is mainly due to the residual flow inertia and can be totally eliminated if flow Reynolds number is less than one.

Affiliations:
Błoński S.-IPPT PAN
Domagalski P.-other affiliation
Kowalewski T.A.-IPPT PAN
4.Kowalewski T.A., Błoński S., Turbulence in micro-channels, ExHFT-7, 7th World Conference on Experimental Heat Transfer, Fluid Mechanics and Thermodynamics, 2009-06-28/07-03, Kraków (PL), pp.361-368, 2009

Conference abstracts
1.Korczyk P.M., Van Steijn V., Błoński S., Kowalewski T.A., Garstecki P., Mechanism of generation of droplets in a T-junction for low capillary numbers, XXI FMC, XXI Fluid Mechanics Conference, 2014-06-15/06-18, Kraków (PL), pp.117, 2014
Keywords:

microfluidics, lab on a chip, droplets, T-junction

Affiliations:
Korczyk P.M.-IPPT PAN
Van Steijn V.-Delft University of Technology (NL)
Błoński S.-IPPT PAN
Kowalewski T.A.-IPPT PAN
Garstecki P.-Institute of Physical Chemistry, Polish Academy of Sciences (PL)
2.Zembrzycki K., Błoński S., Kowalewski T.A., Analysis of wall effect on the process of diffusion of nanopartices in a microchannel, ICTAM XXIII, 23rd International Congress of Theoretical and Applied Mechanics, 2012-08-19/08-24, Beijing (CN), pp.CD-ROM FM10-007, 2012
3.Blim A., Jarecki L., Błoński S., Modeling of pneumatic melt drawing of super-thin fibers in the Lawal nozze, III National Conference of Nano and Micromechanics, 2012-07-04/07-06, Warszawa (PL), pp.77-78, 2012
Abstract:

Pneumatic melt spinning of the fibers by supersonic air jet is an efficient, energy saving method of super-thin fibers formation. In the process with the use of Laval nozzle, the polymer extruded from a raw of orifices in the spinning beam undergoes fast drawn by the pneumatic friction forces. Air velocity, temperature and pressure distributions are computed using k-omega aerodynamic model. Air-drawing dynamics of the polymer bases on the melt spinning model in a single-, thin-filament approximation with the assumption of Phan-Thien/Tanner non-linear viscoelasticity of the melt. Axial velocity, temperature, tensile stress and rheological extra-pressure profiles are computed along the spinning line. Influence of the nozzle geometry, initial air compression, melt extrusion temperature, polymer mass output and the extrusion die diameter is discussed. Influence of the weight average molecular weight, viscosity and relaxation time of the melt is accounted for. Example computations present the role of processing and material characteristics. High cavitating internal extra-pressure is predicted in the melt at high melt elongation rates which may lead to longitudinal burst splitting of the filament. The number of sub-filaments produced by the splitting is estimated reaching nano-fibers thickness range.

Keywords:

superthin fibers, air drawing, pneumatic melt spinning, Laval nozzle

Affiliations:
Blim A.-IPPT PAN
Jarecki L.-IPPT PAN
Błoński S.-IPPT PAN
4.Zembrzycki K., Błoński S., Kowalewski T.A., Analysis of wall effect on the process of diffusion of nanopartices in a microchannel, III National Conference of Nano and Micromechanics, 2012-07-04/07-06, Warszawa (PL), pp.83-84, 2012
5.Kmiotek M., Kucaba-Piętal A., Błoński S., Garstecki P., Jak kształt i geometria przeszkody umieszczonej na ściance mikrokanału zmieniają przepływ?, III National Conference of Nano and Micromechanics, 2012-07-04/07-06, Warszawa (PL), pp.133-134, 2012
6.Jarecki L., Błoński S., Blim A., Zachara A., Modeling of pneumatic melt spinning processes, 4th International Conference on Polymer Behavior, 2010-09-20/09-23, Łódź (PL), 2010
Abstract:

Computer modeling of pneumatic melt spinning of super-thin fibers from crystallizing polymers is presented. Air drawing dynamics of thin polymer streams in melt blowing technology as well as under supersonic air jet in the Laval nozzle is discussed. Hot air jet is used in melt blowing while in the Laval nozzle process cold air is compressed in the nozzle inlet and accelarated to supersonic velocity. Predetermined air fields are simulated using the k-epsilon turbulence model for melt blowing and the k-omega model for the supersonic Laval nozzle processes, with an assumption that the thin polymer filaments do not disturb the air fields substantially. A single-, thin-filament mathematical model of stationary melt spinning is modified for the pneumatic processes and dynamics of the processes is controlled by the axial distributions of the air velocity, temperature and pressure. Effects of non-linear viscoelasticity important for fast flow elongation of polymer melts are accounted for in the model, as well as non-linear stress-orientation relationship and on-line stress induced crystallization of the filament. Example computations are performed for pneumatic formation of polypropylene nonwovens.

Keywords:

pneumatic melt spinning, melt blowing, supersonic air jet, super-thin fibers, oriented crystallization

Affiliations:
Jarecki L.-IPPT PAN
Błoński S.-IPPT PAN
Blim A.-IPPT PAN
Zachara A.-other affiliation