TY - CHAP A1 - Borcia, Ion-Dan A1 - Borcia, Rodica A1 - Bestehorn, Michael A1 - Borcia, C. A1 - Dumitrascu, N. A1 - Egbers, Christoph T1 - Drops on cylindrical surfaces T2 - 7th Conference of the International Marangoni Association, Vienna (Austria), June 23-26, 2014 Y1 - 2014 UR - http://ima7.conf.tuwien.ac.at/AbstractsIMA7.pdf SP - S. 33 PB - Techn. Univ. CY - Vienna ER - TY - JOUR A1 - Borcia, Rodica A1 - Borcia, Ion-Dan A1 - Bestehorn, Michael T1 - Liquid layers on a patterned surface JF - Soft Matter Y1 - 2008 UR - 1744-6848 VL - 4 IS - 12 SP - 2368 EP - 2372 ER - TY - GEN A1 - Borcia, Ion-Dan A1 - Borcia, Rodica A1 - Bestehorn, Michael A1 - Richter, Stefan A1 - Xu, Wenchao A1 - Harlander, Uwe T1 - Horizontal Faraday instability and parametric excitation in a circular channel T2 - GAMM 2019, 90th Annual Meeting of the International Assoociation of Applied Mathematics and Mechanics, February 18-22, 2019, Vienna, Austria Y1 - 2018 UR - https://jahrestagung.gamm-ev.de/images/2019/Photos/GAMM2019_BookofAbstracts.pdf SN - 978-3-903024-84-7 SP - 338 PB - TU Verlag CY - Wien ER - TY - GEN A1 - Borcia, Rodica A1 - Borcia, Ion-Dan A1 - Bestehorn, Michael A1 - Sharma, Deewakar A1 - Amiroudine, Sakir T1 - Phase field modeling in liquid binary mixtures: isothermal and non-isothermal problems T2 - Physical Review Fluids N2 - The objective in the present paper is to study binary fluids with phase field modeling coupled with Navier-Stokes equations. An extended free energy is proposed to account for the continuous path from immiscible to miscible states. We consider fluid pairs that are immiscible for temperatures below the critical one (consolute temperature) and miscible above it. Our extended phase field equation permits us to move from the immiscible state (governed by the Cahn-Hilliard equation) to the miscible state (defined by the species diffusion equation). The scaling of interface tension and interface width with the distance to the critical point is highlighted. The whole system is mechanically excited showing Faraday instability of a flat interface. A linear stability analysis is performed for the stable case (interface waves) as well as for the unstable Faraday one. For the latter, a Floquet analysis shows the well-known Arnold's tongues as a function of the consolute temperature and depth layer. Moreover, two-dimensional finite difference simulations have been performed allowing us to model nonlinear flow patterns both in miscible and immiscible phases. Linear theory and nonlinear simulations show interesting results such as the diminishing of the wavelength of Faraday waves or a shift of the critical vibration amplitude when the consolute temperature is approached. KW - Binary fluids KW - Drop coalescence KW - Drop interactions KW - Drops & bubbles KW - Microfluidics Y1 - 2022 UR - https://journals.aps.org/prfluids/abstract/10.1103/PhysRevFluids.7.064005 U6 - https://doi.org/10.1103/PhysRevFluids.7.064005 SN - 2469-990X VL - 7 IS - 6 SP - 1 EP - 19 ER - TY - GEN A1 - Borcia, Rodica A1 - Popescu, Sebastian A1 - Borcia, Ion-Dan T1 - IMA10: interfacial fluid dynamics and processes T2 - European Physical Journal Special Topics N2 - MA10–special issue presents recent advances on interfacial fluid dynamics with applications in microfluidics, biology, engineering and geophysics. KW - Fluid Dynamics KW - Instabilities Droplets Y1 - 2023 U6 - https://doi.org/10.1140/epjs/s11734-023-00798-5 SN - 1951-6401 SN - 1951-6355 VL - 232 IS - 4 SP - 365 EP - 366 ER - TY - CHAP A1 - Borcia, Ion-Dan A1 - Borcia, Rodica A1 - Bestehorn, Michael A1 - Xu, Wenchao A1 - Harlander, Uwe T1 - Surface waves generated by libration in a circular channel T2 - The 12th European Fluid Mechanics Conference, 9 September 2018 – 13 September 2018, Vienna, Austria Y1 - 2018 UR - http://info.tuwien.ac.at/efmc12/EFMC12_program_v3.2.pdf ER - TY - GEN A1 - Borcia, Ion-Dan A1 - Borcia, Rodica A1 - Xu, Wenchao A1 - Bestehorn, Michael A1 - Richter, Sebastian A1 - Harlander, Uwe T1 - Undular bores in a large circular channel T2 - European Journal of Mechanics - B/Fluids N2 - An experimental device previously developed for studying rotating baroclinic flows has been used to investigate undular bores formation, propagation and collision. Up to our knowledge this is the first experimental study of undular bores in a circular channel. For a setup without barriers, this geometry accomplishes in a natural way the periodic lateral boundary conditions, very often used in numerical simulations. An excellent agreement between the experiment and simulation has been achieved. The spatio-temporal structure of bores is well reproduced for the first few reflections or collisions. KW - Undular bores KW - Bore collision KW - Periodical boundary conditions Y1 - 2020 UR - https://www.sciencedirect.com/science/article/pii/S0997754619300706?via%3Dihub U6 - https://doi.org/10.1016/j.euromechflu.2019.09.003 SN - 0997-7546 VL - 79 SP - 67 EP - 73 ER - TY - GEN A1 - Borcia, Ion-Dan A1 - Richter, Sebastian A1 - Borcia, Rodica A1 - Schön, Franz-Theo A1 - Harlander, Uwe A1 - Bestehorn, Michael T1 - Wave propagation in a circular channel: sloshing and resonance T2 - The European Physical Journal Special Topics N2 - Surface wave resonance of a liquid (water) layer confined in a circular channel is studied both experimentally and numerically. For the experiment, eight unevenly distributed ultrasonic distance sensors measure the local height of the wave surface. The resonance curves show maxima only for odd multiples of the fundamental resonance frequency . We explained this behavior using a simple intuitive “ping-pong” like model. Collision of wave fronts can be observed for higher frequencies. Also, the wave reflection on the walls can be treated as wave collision with itself. The non-linearity seems to be weak in our study so the delay in the wave propagation before and after the collision is small. Time-space plots show localized propagating waves with high amplitudes for frequencies near resonance. Between the peaks low amplitude and harmonic patterns are observed. However, for higher frequencies, the frequency band for localized waves becomes wider. In the Fourier space-time plane, this can be observed as a point for the harmonic patterns or a superposition of two lines: one line parallel to wave-vector k axis corresponding to the excitation frequency and a second line with inclination given by wave propagation velocity . For planned future work, this result will help us to reconstruct the whole water surface elevation using time-series from only a few measurement points Y1 - 2023 UR - https://link.springer.com/article/10.1140/epjs/s11734-023-00790-z U6 - https://doi.org/10.1140/epjs/s11734-023-00790-z SN - 1951-6401 SN - 1951-6355 VL - Vol. 232 IS - 4 SP - 461 EP - 468 ER - TY - GEN A1 - Borcia, Ion-Dan A1 - Borcia, Rodica A1 - Richter, Sebastian A1 - Xu, Wenchao A1 - Bestehorn, Michael A1 - Harlander, Uwe T1 - Horizontal Faraday instability in a circular channel T2 - Proceedings in Applied Mathematics and Mechanics (PAMM) N2 - We study surface waves in a circular channel placed on a rotating table. The tank can rotate with constant velocity and/or can oscillate. For a glycerin‐water‐solution with high viscosity, oscillation amplitudes about 20 cm and frequencies of 0.5 Hz, we observe surface patterns generated by a parametric instability. The circular geometry of the channel assures in a natural way the periodic lateral boundary conditions often used in the numerical simulations. Up to our knowledge this is the first experiment which evidences the horizontal Faraday instability in a container without walls blocking the flow in the oscillation direction. Experimental and numerical results are compared and discussed. KW - Faraday instability KW - Numerical solutions Y1 - 2019 UR - https://onlinelibrary.wiley.com/doi/abs/10.1002/pamm.201900242 U6 - https://doi.org/10.1002/pamm.201900242 SN - 1617-7061 VL - 19 IS - 1 ER - TY - GEN A1 - Borcia, Rodica A1 - Borcia, Ion-Dan A1 - Bestehorn, Michael T1 - Can vibrations control drop motion? T2 - Langmuir N2 - We discuss a mechanism for controlled motion of drops with applications for microfluidics and microgravity. The mechanism is the following: a solid plate supporting a liquid droplet is simultaneously subject to lateral and vertical harmonic oscillations. In this way the symmetry of the back-and-forth droplet movement along the substrate under inertial effects is broken and thus will induce a net driven motion of the drop. We study the dependency of the traveled distance on the oscillation parameters (forcing amplitude, frequency, and phase shift between the two perpendicular oscillations) via phase field simulations. The internal flow structure inside the droplet is also investigated. We make predictions on resonance frequencies for drops on a substrate with a varying wettability. Y1 - 2014 UR - http://pubs.acs.org/doi/abs/10.1021/la503415r U6 - https://doi.org/10.1021/la503415r SN - 1520-5827 SN - 1864-5631 VL - 30 IS - 47 SP - 14113 EP - 14117 ER - TY - JOUR A1 - Borcia, Rodica A1 - Borcia, Ion-Dan A1 - Bestehorn, Michael T1 - Drops on an arbitrarily wetting substrate: A phase field description Y1 - 2008 ER - TY - GEN A1 - Borcia, Rodica A1 - Borcia, Ion-Dan A1 - Bestehorn, Michael A1 - Varlamova, Olga A1 - Hoefner, Kevin A1 - Reif, Jürgen T1 - Drop Behavior Influenced by the Correlation Length on Noisy Surfaces T2 - Langmuir Y1 - 2019 U6 - https://doi.org/10.1021/acs.langmuir.8b03878 VL - 35 SP - 928 EP - 934 ER - TY - GEN A1 - Varlamova, Olga A1 - Reif, Jürgen A1 - Stolz, Michael A1 - Borcia, Rodica A1 - Borcia, Ion-Dan A1 - Bestehorn, Michael T1 - Wetting properties of LIPSS structured silicon surfaces T2 - The European Physical Journal B N2 - The controlled dynamics of liquid drops via generation of specific wetting states on a solid surface is of great interests both in the fundamental and applied sciences. Considering that the wettability is strongly dependent on the surface topography and surface roughness, we investigate – through experiments and theory – the effect of laser-induced periodic surface structures (LIPSS) generated on silicon (100) targets as a control parameter of wetting properties. To obtain structured silicon surfaces with different morphological features, we patterned the surface by irradiation with femtosecond pulses from an amplified Ti:Sapphire laser system (790 nm/100 fs/1 kHz) at a fluence in the range of 0.4–1.2 J/cm2 on a spot with a diameter about of 100 μm. Variation of the applied irradiation dose results in surface modifications with the roughness about of a few tens of nanometers are ranging from regular LIPSS patterns with the lateral period of about 500–700 nm to complex agglomerations of 3-D microstructures with several-μm feature size. The theoretical study on the correlation of wetting properties with the surface topography has been performed within a phase field model. We found an excellent agreement of numerical results with experiments. Y1 - 2019 U6 - https://doi.org/10.1140/epjb/e2019-90672-2 SN - 1434-6036 SN - 1434-6028 VL - 92 IS - 5 ER - TY - GEN A1 - Borcia, Rodica A1 - Borcia, Ion-Dan A1 - Helbig, Markus A1 - Meier, Martin A1 - Egbers, Christoph A1 - Bestehorn, Michael T1 - Dancing drops over vibrating substrates T2 - The European Physical Journal Special Topics KW - Thin Film Instabilities Y1 - 2017 UR - https://link.springer.com/article/10.1140/epjst/e2016-60202-6 U6 - https://doi.org/10.1140/epjst/e2016-60202-6 SN - 1951-6355 SN - 1951-6401 VL - 226 IS - 6 SP - 1297 EP - 1306 ER - TY - GEN A1 - Borcia, Rodica A1 - Borcia, Ion-Dan A1 - Bestehorn, Michael T1 - Nonlinear dynamics of thin liqiud films consisting of two miscible components T2 - Physical Review E N2 - Recently, we systematically derived a system of two coupled conservation equations governing a thin liquid layer with a deformable surface composed of two completely miscible components [Phys. Fluids 22, 104102 (2010)]. One equation describes the location of the free surface and the second one the evolution of the mean concentration. This lubrication model was investigated previously in linearized form. The study is now extended to the fully nonlinear case of thin liquid films of a binary mixture (in one and two horizontal spatial dimensions) with and without heat transport. For an initially flat and motionless film heated from below, we analyze the component separation induced by the Soret effect. Nonlinear simulations show that the Soret effect can cause a multitude of interesting behaviors, such as oscillatory patterns and solitonlike structures (localized traveling drops or holes). A stronger component separation induced by stronger Soret effects favors faster-moving localized structures. For isothermal systems, we study the fusion and the mixing of two thin liquid films of different but perfectly miscible liquids. Marangoni-driven forces can cause delayed coalescence, ripple formation, and fingering patterns at the borderline between the two liquid layers. A systematic analysis for ripple pattern formation and finger instabilities at different diffusion constants shows that these phenomena appear more pronounced for lower diffusion in the system. Y1 - 2012 UR - http://journals.aps.org/pre/abstract/10.1103/PhysRevE.86.056319 U6 - https://doi.org/10.1103/PhysRevE.86.056319 SN - 2470-0053 VL - 86 IS - 5 SP - 056319 ER - TY - JOUR A1 - Borcia, Ion-Dan A1 - Borcia, Rodica A1 - Bestehorn, Michael T1 - Long wave instabilities in binary mixture thin liquid films Y1 - 2006 ER - TY - JOUR A1 - Borcia, Ion-Dan A1 - Borcia, Rodica A1 - Bestehorn, Michael T1 - Soret effect in thin liquid films:Localized running drops, holes and stripes Y1 - 2006 ER - TY - CHAP A1 - Borcia, Ion-Dan A1 - Borcia, Rodica A1 - Bestehorn, Michael A1 - Egbers, Christoph T1 - Drops on cylindrical wires T2 - International Topical Team Workshop on Two-Phase Systems for Ground and Space Applications, ITTW 2013 Y1 - 2013 UR - http://www.zarm.uni-bremen.de/ITTW2013/abstracts/ITTW2013_Book-of-Abstracts.pdf ER - TY - JOUR A1 - Borcia, Rodica A1 - Merkt, Domnic A1 - Bestehorn, Michael T1 - Convective patterns in liquid-vaporsystems with diffuse interface Y1 - 2006 ER - TY - GEN A1 - Bestehorn, Michael A1 - Sharma, Deewakar A1 - Borcia, Rodica A1 - Amiroudine, Sakir T1 - Faraday instability of binary miscible/immiscible fluids with phase field approach T2 - Physical Review Fluids N2 - The objective in the present paper is to study binary fluids with phase field modeling coupled with Navier-Stokes equations. An extended free energy is proposed to account for the continuous path from immiscible to miscible states. We consider fluid pairs that are immiscible for temperatures below the critical one (consolute temperature) and miscible above it. Our extended phase field equation permits us to move from the immiscible state (governed by the Cahn-Hilliard equation) to the miscible state (defined by the species diffusion equation). The scaling of interface tension and interface width with the distance to the critical point is highlighted. The whole system is mechanically excited showing Faraday instability of a flat interface. A linear stability analysis is performed for the stable case (interface waves) as well as for the unstable Faraday one. For the latter, a Floquet analysis shows the well-known Arnold's tongues as a function of the consolute temperature and depth layer. Moreover, two-dimensional finite difference simulations have been performed allowing us to model nonlinear flow patterns both in miscible and immiscible phases. Linear theory and nonlinear simulations show interesting results such as the diminishing of the wavelength of Faraday waves or a shift of the critical vibration amplitude when the consolute temperature is approached. KW - Binary fluids KW - Hydrodynamic waves KW - Instability of free-surface flows KW - Surface tension effects Y1 - 2021 UR - https://journals.aps.org/prfluids/abstract/10.1103/PhysRevFluids.6.064002 U6 - https://doi.org/10.1103/PhysRevFluids.6.064002 SN - 2469-990X VL - 6 IS - 6 SP - 1 EP - 26 ER - TY - GEN A1 - Borcia, Rodica A1 - Menzel, Stefan A1 - Bestehorn, Michael A1 - Karpitschka, Stefan A1 - Riegler, Horst T1 - Delayed coalescence of droplets with miscible liquids: Lubrication and phasefield theories T2 - European Physical Journal E Y1 - 2011 SN - 1292-8941 VL - 34 IS - 3 SP - 11024-9 ER - TY - JOUR A1 - Borcia, Rodica A1 - Bestehorn, Michael T1 - Phase field models for Marangoni convection in planar layers Y1 - 2006 ER - TY - JOUR A1 - Borcia, Rodica A1 - Merkt, Domnic A1 - Bestehorn, Michael T1 - A phase-field description of surface-tension-driven instability Y1 - 2004 ER - TY - JOUR A1 - Borcia, Rodica A1 - Bestehorn, Michael T1 - Phase-field model for Marangoni convection in liquid-gas systems with deformable interface Y1 - 2003 ER - TY - GEN A1 - Borcia, Rodica A1 - Bestehorn, Michael T1 - A phase field description of self-propulsion of twin sessile drops induced by surface tension gradients T2 - Fluid Dynamics Research N2 - We describe the self-propulsion of two sessile drops induced by surface tension gradients at the droplet interfaces using a three-dimensional phase field model. We study the problem for the low viscosity regime when the width of the connecting neck between the interacting drops increases linearly with increasing t1/2 and the merger is dominated by capillary forces. We investigate the dependence of the displacement achieved by self-propulsion on viscous shearing as well as the internal flow structure during the coalescence process. KW - Drops Y1 - 2014 UR - http://iopscience.iop.org/article/10.1088/0169-5983/46/4/041405/meta U6 - https://doi.org/10.1088/0169-5983/46/4/041405 SN - 0169-5983 VL - 46 IS - 4 SP - 041405 ER - TY - GEN A1 - Borcia, Rodica A1 - Bestehorn, Michael T1 - Phase field modelling of non-equilibrium patterns on the surface of a liquid film under lateral oscillations at the substrate T2 - International Journal of Bifurcation and Chaos N2 - We use a phase field model which couples the generalized Navier–Stokes equation (including the Korteweg stress tensor) with the continuity equation for studying nonlinear pattern formation on the surface of a liquid film under (linear and circular) lateral harmonic vibrations at the solid substrate. First, we prove the thermodynamic consistency of our phase field model. Next, we present computer simulations in three spatial dimensions. We illustrate nonequilibrium patterns at the instability onset, confirming in this way the results recently reported in Phys. Rev. E 88, 023025 (2013). The lateral profiles of the deflected surface are compared with those reported in J. Fluid Mech. 686, 409 (2011) for Faraday instability excited by vertical harmonic vibrations at the bottom plate. Y1 - 2014 UR - http://www.worldscientific.com/doi/abs/10.1142/S0218127414501107 U6 - https://doi.org/10.1142/S0218127414501107 SN - 0218-1274 SN - 1793-6551 VL - 24 IS - 9 SP - 1450110 ER - TY - GEN A1 - Borcia, Rodica A1 - Bestehorn, Michael T1 - Partial coalescence of sessile drops with different miscible liquids T2 - Langmuir N2 - Using computer simulations in three spatial dimensions, we examine the interaction between two deformable drops consisting of two perfectly miscible liquids sitting on a solid substrate under a given contact angle. Driven by capillarity and assisted by Marangoni effects at the droplet interfaces, several distinct coalescence regimes are achieved after the droplets’ collision. Y1 - 2013 UR - http://pubs.acs.org/doi/full/10.1021/la3050835?src=recsys U6 - https://doi.org/10.1021/la3050835 SN - 1520-5827 VL - 29 IS - 14 SP - 4426 EP - 4429 ER - TY - GEN A1 - Borcia, Rodica A1 - Bestehorn, Michael T1 - Numerical simulations on delayed coalescence of droplets in confinedgeometries Y1 - 2010 ER - TY - GEN A1 - Borcia, Rodica A1 - Bestehorn, Michael T1 - Controlled Pattern Formation in Thin Liquid Layers Y1 - 2009 ER - TY - JOUR A1 - Borcia, Rodica A1 - Bestehorn, Michael T1 - Phase field models and Marangoni flows Y1 - 2007 ER - TY - GEN A1 - Borcia, Rodica A1 - Bestehorn, Michael T1 - A Phase Field Description of Spatio-Temporal Behavior in Thin Liquid Layers Y1 - 2010 ER - TY - JOUR A1 - Borcia, Rodica A1 - Bestehorn, Michael T1 - Phase field simulations for drops and bubbles Y1 - 2007 ER - TY - GEN A1 - Borcia, Rodica A1 - Bestehorn, Michael T1 - On the coalescence of sessile drops with miscible liquids T2 - European Physical Journal E Y1 - 2011 SN - 1292-8941 VL - 34 IS - 8 SP - 81 ER - TY - GEN A1 - Borcia, Rodica A1 - Bestehorn, Michael T1 - Different behaviours of delayed fusion between drops with miscible liquids T2 - Physical review E Y1 - 2010 SN - 1063-651X VL - 82 IS - 3 SP - 036312 ER - TY - JOUR A1 - Borcia, Rodica A1 - Bestehorn, Michael T1 - Phase-field simulations for evaporation with convection in liquid-vapor systems JF - The European physical journal B Y1 - 2005 SN - 1434-6028 VL - 44 IS - 1 SP - 101 EP - 108 ER - TY - CHAP A1 - Borcia, Rodica A1 - Bestehorn, Michael A1 - Egbers, Christoph T1 - Surface effects at the mixing of two perfectly miscible components in a thin liquid film T2 - International Topical Team Workshop on Two-Phase Systems for Ground and Space Applications, ITTW 2013 Y1 - 2013 UR - http://www.zarm.uni-bremen.de/ITTW2013/abstracts/ITTW2013_Book-of-Abstracts.pdf ER - TY - GEN A1 - Borcia, Rodica A1 - Bestehorn, Michael A1 - Uhlig, Sebastian A1 - Gaudet, Matthieu A1 - Schenk, Harald T1 - Liquid pumping induced by transverse forced vibrations of an elastic beam: A lubrication approach T2 - Physical Review Fluids N2 - Two liquid pumps are investigated theoretically and numerically: a single thin liquid layer actuated by a periodic force at an elastic beam and a two-layer geometry actuated by an elastic beam. For the second geometry, the beam actuates the liquid from both sides. For both pumps, the liquid film thickness is small compared to the lateral characteristic length of the system. A lubrication theory is developed. The Euler-Bernoulli equation for transverse deformations of an elastic beam is coupled to the fundamental hydrodynamic equations: the Navier-Stokes equation and a continuity equation in the long-wave approximation. In this way, one connects the transverse displacement of the beam with the hydrodynamic quantities (pressure, velocity fields, and flow rates). Appropriate boundary conditions incorporate the function of the valves. The derivation of the theoretical model is followed by numerical simulations. We estimate flow rates (in two and three spatial dimensions) for different system parameters and we compute the efficiency of a well-designed liquid pump. KW - Microfluidic devices KW - Thin fluid films Y1 - 2018 UR - https://journals.aps.org/prfluids/abstract/10.1103/PhysRevFluids.3.084202 U6 - https://doi.org/10.1103/PhysRevFluids.3.084202 SN - 2469-990X VL - 3 IS - 8 ER -