TY - GEN A1 - Pototsky, Andrey A1 - Archer, Andrew J. A1 - Bestehorn, Michael A1 - Merkt, Domnic A1 - Savelev, S. A1 - Marchesoni, F. T1 - Collective shuttling of attracting particles in asymmetric narrow channels Y1 - 2010 ER - TY - GEN A1 - Pototsky, Andrey A1 - Oron, Alexander A1 - Bestehorn, Michael T1 - Equilibrium shapes and floatability of static and vertically vibrated heavy liquid drops on the surface of a lighter fluid T2 - Journal of Fluid Mechanics N2 - A small drop of a heavier fluid may float on the surface of a lighter fluid supported by surface tension forces. In equilibrium, the drop assumes a radially symmetric shape with a circular triple-phase contact line. We show that such a floating liquid drop with a sufficiently small volume has two distinct equilibrium shapes at terrestrial gravity: one with a larger and one with a smaller radius of the triple-phase contact line. Static stability analysis reveals that both shapes could be stable if the drop volume is below a certain critical value. Experiments conducted with μL-sized water drops floating on commercial oil support the existence of multiple contact line radii for a drop with fixed volume. Next, we experimentally study the floatability of a less viscous water drop on the surface of a more viscous and less dense oil, subjected to a low-frequency (Hz-order) vertical vibration. We find that in a certain range of amplitudes, vibration helps heavy liquid drops to stay afloat. The physical mechanism of the increased floatability is explained by the horizontal elongation of the drop driven by subharmonic Faraday waves. The average length of the triple-phase contact line increases as the drop elongates that leads to a larger average lifting force produced by the surface tension. KW - Drops KW - Faraday waves Y1 - 2021 U6 - https://doi.org/10.1017/jfm.2021.546 SN - 1469-7645 SN - 0022-1120 VL - 922 SP - A31-1 EP - A31-21 ER - TY - GEN A1 - Bestehorn, Michael A1 - Pototsky, Andrey T1 - Faraday instability and nonlinear pattern formation of a two-layer system: A reduced model T2 - Physical Review Fluids N2 - Stability and pattern formation of a two-layer liquid system with large aspect ratio subjected to vertical harmonic oscillations is studied by means of an integrated boundary layer model. The lower layer rests on an oscillating solid substrate, the upper layer is separated by a deformable interface from the lower layer and bounded at the top with a second, free interface to the ambient passive air. The model is derived from the Navier-Stokes equations in long-wave approximation, including inertial terms. Applying a Floquet analysis, linear stability charts and dispersion relations are computed and compared with results from the full linearized Navier-Stokes equations and the long-wave approximation. Nonlinear Faraday patterns simultaneously occurring at the interface and at the film surface are studied by numerically solving the integrated boundary layer model in two and three spatial dimensions. For gravitationally stable two-layer films with a lighter fluid on top of the heavier fluid, we find squares, hexagons, quasiperiodic patterns with eightfold symmetry as well as localized states in the form of large scale depletion regions or finite depth holes, occurring at the interface and surface. For a Rayleigh-Taylor unstable combination (heavier fluid above the light one) we show that external vibration increases the lifetime of the film by delaying or completely suppressing the film rupture. Y1 - 2016 UR - http://journals.aps.org/prfluids/abstract/10.1103/PhysRevFluids.1.063905 U6 - https://doi.org/10.1103/PhysRevFluids.1.063905 SN - 2469-990X VL - 1 IS - 6 SP - 063905-1 EP - 063905-24 ER - TY - GEN A1 - Pototsky, Andrey A1 - Bestehorn, Michael T1 - Faraday instability of a two-layer liquid film with a free upper surface T2 - Physical Review Fluids N2 - We study the linear stability of a laterally extended flat two-layer liquid film under the influence of external vertical vibration. The first liquid layer rests on a vibrating solid plate and is overlaid by a second layer of immiscible fluid with deformable upper surface. Surface waves, excited as the result of the Faraday instability, can be characterized by a time-dependent relative amplitude of the displacements of the liquid-liquid and the liquid-gas interfaces. The in-phase displacements are associated with a zigzag (barotropic) mode and the antiphase displacement corresponds to the varicose thinning mode. We numerically determine the stability threshold in the vibrated two-layer film and compute the dispersion relation together with the decay rates of the surface waves in the absence of vibration. The in-phase and the antiphase displacements are strongly coupled in the vibrated system. The interplay between the Faraday and the Rayleigh-Taylor instabilities in the system with heavier fluid on top of a lighter fluid is analyzed. Y1 - 2016 UR - http://journals.aps.org/prfluids/abstract/10.1103/PhysRevFluids.1.023901 U6 - https://doi.org/10.1103/PhysRevFluids.1.023901 SN - 2469-990X VL - 1 IS - 2 SP - 023901-1 EP - 023901-18 ER - TY - GEN A1 - Pototsky, Andrey A1 - Oron, Alexander A1 - Bestehorn, Michael T1 - Vibration-induced floatation of a heavy liquid drop on a lighter liquid film T2 - Physic of Fluids N2 - We carry out a theoretical study of vibration-induced saturation of the Rayleigh-Taylor instability for an isolated liquid drop on the surface of a less dense finite-thickness carrier film. Without vibration, a heavy drop falls through the carrier film by forming a stretching liquid column until the bottom tip of the column reaches the solid substrate and the carrier film ruptures. We show that an externally applied vertical vibration prevents the rupture of the film and enables stable flotation of the drop. A hydrodynamic model is used to study the effect of inertia on the long-time dynamics of the drop. It is shown that rupture can only be prevented when the Reynolds number is nonzero. KW - Wave mechanics KW - Thin films KW - Liquid liquid interfaces KW - Liquid solid interfaces KW - Flow instabilities KW - Navier Stokes equations KW - Oscillating flow KW - Surface waves KW - Hydrodynamics simulations Y1 - 2019 UR - https://pubs.aip.org/aip/pof/article/31/8/087101/1059058/Vibration-induced-floatation-of-a-heavy-liquid U6 - https://doi.org/10.1063/1.5099661 SN - 1089-7666 SN - 1070-6631 VL - 31 IS - 8 SP - 087101-1 EP - 087101-13 ER - TY - GEN A1 - Pototsky, Andrey A1 - Bestehorn, Michael T1 - Shaping liquid drops by vibration T2 - epl : a letters journal exploring the frontiers of physics N2 - We present and analyze a minimal hydrodynamic model of a vertically vibrated liquid drop that undergoes dynamic shape transformations. In agreement with experiments, a circular lens-shaped drop is unstable above a critical vibration amplitude, spontaneously elongating in the horizontal direction. Smaller drops elongate into localized states that oscillate with half of the vibration frequency. Larger drops evolve by transforming into a snake-like structure with gradually increasing length. The worm state is long-lasting with a potential to fragment into smaller drops. KW - Thin Films KW - Drop formation Y1 - 2018 UR - http://iopscience.iop.org/article/10.1209/0295-5075/121/46001#epl19033s1 U6 - https://doi.org/10.1209/0295-5075/121/46001 SN - 1286-4854 SN - 0302-072X VL - 121 IS - 4 SP - 46001-p1 EP - 46001-p6 ER - TY - JOUR A1 - Bestehorn, Michael A1 - Pototsky, Andrey A1 - Thiele, Uwe T1 - 3D Large scale Marangoni convection in liquid films Y1 - 2003 ER - TY - JOUR A1 - Merkt, Domnic A1 - Pototsky, Andrey A1 - Bestehorn, Michael A1 - Thiele, Uwe T1 - Long-wave theory of bounded two-layer films with a free liquid-liquid interface: Short and long-time evolution Y1 - 2005 U6 - https://doi.org/10.1063/1.1935487 ER - TY - JOUR A1 - Pototsky, Andrey A1 - Bestehorn, Michael A1 - Merkt, Domnic A1 - Thiele, Uwe T1 - Alternative pathways of dewetting for a thin two-layer film of soft matter Y1 - 2004 U6 - https://doi.org/10.48550/arXiv.nlin/0401042 ER - TY - JOUR A1 - Pototsky, Andrey A1 - Bestehorn, Michael A1 - Merkt, Domnic A1 - Thiele, Uwe T1 - Evolution of interface patterns of three-dimensional two-layer liquid films JF - Europhysics Letters Y1 - 2006 U6 - https://doi.org/10.1209/epl/i2006-10026-8 SN - 0302-072X VL - 74 IS - 4 SP - 665 EP - 671 ER - TY - JOUR A1 - Pototsky, Andrey A1 - Bestehorn, Michael A1 - Thiele, Uwe T1 - Control of the structuring of thin softmatter films by means of different types of external disturbance Y1 - 2004 ER - TY - THES A1 - Pototsky, Andrey T1 - Pattern Formation in Thin One- and Two-layer Liquid Films Y1 - 2005 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:co1-000000822 PB - Brandenburgische Techn. Univ. CY - Cottbus ER -