Serge Barral, Ph.D., Eng.


Recent publications
1.Barral S., Peradzyński Z., Ionization oscillations in Hall accelerators, PHYSICS OF PLASMAS, ISSN: 1070-664X, DOI: 10.1063/1.3292645, Vol.17, pp.014505-4, 2010
Abstract:

The underlying mechanism of low-frequency oscillations in Hall accelerators is investigated theoretically. It is shown that relaxation oscillations arise from a competition between avalancheionization and the advective transport of the working gas. The model derived recovers the slow progression and fast recession of the ionization front. Analytical approximations of the shape of current pulses and of the oscillation frequency are provided for the case of large amplitude oscillations.

Affiliations:
Barral S.-IPPT PAN
Peradzyński Z.-other affiliation
2.Peradzyński Z., Barral S., Makowski K., Dudeck M., Causality violation in analysis of Hall thruster plasma instabilities, JOURNAL OF TECHNICAL PHYSICS, ISSN: 0324-8313, Vol.49, pp.315-327, 2009
3.Kowalewski T.A., Barral S., Modelling electrospinning of nanofibres, Proceedings in Applied Mathematics and Mechanics, ISSN: 1617-7061, DOI: 10.1002/pamm.200910204, Vol.9, pp.463-464, 2009
Abstract:

Electrospinning is based on so-called bending instability which results in an erratic spiralling motion of the liquid jet as it proceeds towards a collecting electrode, where it is eventually de posited as a mat of micro/nanosized fibres. Most electrospinning models formulated within the slender approximation rely, however, on an inconsistent description of electrostatic interactions which renders them grossly inappropriate whenever the discretization is either too coarse or too fine. The present work aims at proposing a discrete slender model which is numerically consistent (allowing use of arbitrary fine meshes) and remains accurate even for coarse meshes. At the same time, efficient numerical techniques based on hierarchical charge clustering are introduced that drastically decrease computational times. Finally, a versatile boundary value method is implemented to enforce fixed-potential boundary conditions, allowing realistic electrode configurations to be investigated.

Keywords:

Electrospinning numerical model, boundary value method, bending instability

Affiliations:
Kowalewski T.A.-IPPT PAN
Barral S.-IPPT PAN
4.Peradzyński Z., Barral S., Makowski K., Dudeck M., Causality violation in analysis of Hall thruster plasma instabilities, JOURNAL OF TECHNICAL PHYSICS, ISSN: 0324-8313, Vol.49, pp.315-327, 2008
5.Peradzyński Z., Makowski K., Barral S., Kurzyna J., Dudeck M., The role of the electron energy balance in plasma thruster instabilities, AIP Conference Proceedings, ISSN: 0094-243X, DOI: 10.1063/1.2909169, Vol.993, pp.435, 2008
Abstract:

Using the fluid equations of Hall thruster plasma we analyze the influence of the electron energy balance on the stability of ion sound modes. For frequencies lower than ωc = 107 s−1 the gains and losses in the source term are approximately equal, thus the temperature can be in principle determined in terms of other dependent variables. This permits to reduce the number of equations. It appears however, that the new system can have complex characteristics in some regions. This in turn implies instability of certain modes with frequencies lower than ωc.

Keywords:

Energy balance, Acoustic analysis, Fluid equations, Instability analysis, Plasma instabilities

Affiliations:
Peradzyński Z.-IPPT PAN
Makowski K.-IPPT PAN
Barral S.-IPPT PAN
Kurzyna J.-IPPT PAN
Dudeck M.-CNRS (FR)
6.Barral S., Makowski K., Peradzyński Z., Dudeck M., Transit time instability in Hall Thruster, PHYSICS OF PLASMAS, ISSN: 1070-664X, Vol.12, pp.73504-1-9, 2005
7.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 chapters in recent monographs
1.
158
Kowalewski T.A., Barral S., Kowalczyk T., IUTAM Symposium on modelling nanomaterials and nanosystems, IUTAM Bookseries, rozdział: Modeling electrospinning of nanofibers, Springer, Pyrz R., Rauhe J.C. (Eds.), 13, pp.279-292, 2009

Conference papers
1.Kowalewski T.A., Barral S., Kowalczyk T., Modeling Electrospinning of Nanofibers, in Modelling Nanomaterials and Nanosystems, IUTAM Symposium, 2009-05-19/05-22, Aalborg (DK), Vol.13, pp.279-292, 2009
Abstract:

A fast discrete model for the simulations of thin charged jets produced during the electrospinning process is derived, based on an efficient implementation of the boundary element method for the computation of electrostatic interactions of the jet with itself and with the electrodes. Short-range electrostatic forces are evaluated with slender-body analytical approximations, whereas a hierarchical force evaluation algorithm is used for long-range interactions. Qualitative comparisons with experiments is discussed.

Keywords:

modelling electrospinning, electrostatic interactions, BEM

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

Patents
Numer/data zgłoszenia patentowego
Ogłoszenie o zgłoszeniu patentowym
Twórca / twórcy
Tytuł
Kraj i Nazwa uprawnionego z patentu
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Ogłoszenie o udzieleniu patentu
pdf
0953370
2009-05-20
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Barral S., Zurbach S.
Silnik plazmowy typu Hall’a
FR, Snecma (Francja), Instytut Podstawowych Problemów Techniki PAN, CNES (Francja), CNRS (Francja)
PCT/FR2010/050963
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2010-05-19