@inproceedings{BorciaBorciaBestehornetal., author = {Borcia, Ion-Dan and Borcia, Rodica and Bestehorn, Michael and Borcia, C. and Dumitrascu, N. and Egbers, Christoph}, title = {Drops on cylindrical surfaces}, series = {7th Conference of the International Marangoni Association, Vienna (Austria), June 23-26, 2014}, booktitle = {7th Conference of the International Marangoni Association, Vienna (Austria), June 23-26, 2014}, publisher = {Techn. Univ.}, address = {Vienna}, pages = {S. 33}, language = {en} } @article{BorciaBorciaBestehorn, author = {Borcia, Rodica and Borcia, Ion-Dan and Bestehorn, Michael}, title = {Drops on an arbitrarily wetting substrate: A phase field description}, language = {en} } @article{BorciaBorciaBestehorn, author = {Borcia, Rodica and Borcia, Ion-Dan and Bestehorn, Michael}, title = {Liquid layers on a patterned surface}, series = {Soft Matter}, volume = {4}, journal = {Soft Matter}, number = {12}, pages = {2368 -- 2372}, language = {en} } @article{BorciaBorciaBestehorn, author = {Borcia, Ion-Dan and Borcia, Rodica and Bestehorn, Michael}, title = {Long wave instabilities in binary mixture thin liquid films}, language = {en} } @article{BorciaBorciaBestehorn, author = {Borcia, Ion-Dan and Borcia, Rodica and Bestehorn, Michael}, title = {Soret effect in thin liquid films:Localized running drops, holes and stripes}, language = {en} } @inproceedings{BorciaBorciaBestehornetal., author = {Borcia, Ion-Dan and Borcia, Rodica and Bestehorn, Michael and Egbers, Christoph}, title = {Drops on cylindrical wires}, series = {International Topical Team Workshop on Two-Phase Systems for Ground and Space Applications, ITTW 2013}, booktitle = {International Topical Team Workshop on Two-Phase Systems for Ground and Space Applications, ITTW 2013}, language = {en} } @misc{BorciaBorciaBestehorn, author = {Borcia, Rodica and Borcia, Ion-Dan and Bestehorn, Michael}, title = {Nonlinear dynamics of thin liqiud films consisting of two miscible components}, series = {Physical Review E}, volume = {86}, journal = {Physical Review E}, number = {5}, issn = {2470-0053}, doi = {10.1103/PhysRevE.86.056319}, pages = {056319}, abstract = {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.}, language = {en} } @misc{BorciaBorciaBestehorn, author = {Borcia, Rodica and Borcia, Ion-Dan and Bestehorn, Michael}, title = {Can vibrations control drop motion?}, series = {Langmuir}, volume = {30}, journal = {Langmuir}, number = {47}, issn = {1520-5827}, doi = {10.1021/la503415r}, pages = {14113 -- 14117}, abstract = {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.}, language = {en} } @misc{BorciaBorciaHelbigetal., author = {Borcia, Rodica and Borcia, Ion-Dan and Helbig, Markus and Meier, Martin and Egbers, Christoph and Bestehorn, Michael}, title = {Dancing drops over vibrating substrates}, series = {The European Physical Journal Special Topics}, volume = {226}, journal = {The European Physical Journal Special Topics}, number = {6}, issn = {1951-6355}, doi = {10.1140/epjst/e2016-60202-6}, pages = {1297 -- 1306}, language = {en} } @inproceedings{BorciaBorciaBestehornetal., author = {Borcia, Ion-Dan and Borcia, Rodica and Bestehorn, Michael and Xu, Wenchao and Harlander, Uwe}, title = {Surface waves generated by libration in a circular channel}, series = {The 12th European Fluid Mechanics Conference, 9 September 2018 - 13 September 2018, Vienna, Austria}, booktitle = {The 12th European Fluid Mechanics Conference, 9 September 2018 - 13 September 2018, Vienna, Austria}, pages = {1}, language = {en} } @misc{BorciaBorciaBestehornetal., author = {Borcia, Rodica and Borcia, Ion-Dan and Bestehorn, Michael and Varlamova, Olga and Hoefner, Kevin and Reif, J{\"u}rgen}, title = {Drop Behavior Influenced by the Correlation Length on Noisy Surfaces}, series = {Langmuir}, volume = {35}, journal = {Langmuir}, doi = {10.1021/acs.langmuir.8b03878}, pages = {928 -- 934}, language = {en} } @misc{BorciaBorciaBestehornetal., author = {Borcia, Ion-Dan and Borcia, Rodica and Bestehorn, Michael and Richter, Stefan and Xu, Wenchao and Harlander, Uwe}, title = {Horizontal Faraday instability and parametric excitation in a circular channel}, series = {GAMM 2019, 90th Annual Meeting of the International Assoociation of Applied Mathematics and Mechanics, February 18-22, 2019, Vienna, Austria}, journal = {GAMM 2019, 90th Annual Meeting of the International Assoociation of Applied Mathematics and Mechanics, February 18-22, 2019, Vienna, Austria}, publisher = {TU Verlag}, address = {Wien}, isbn = {978-3-903024-84-7}, pages = {338}, language = {en} } @misc{VarlamovaReifStolzetal., author = {Varlamova, Olga and Reif, J{\"u}rgen and Stolz, Michael and Borcia, Rodica and Borcia, Ion-Dan and Bestehorn, Michael}, title = {Wetting properties of LIPSS structured silicon surfaces}, series = {The European Physical Journal B}, volume = {92}, journal = {The European Physical Journal B}, number = {5}, issn = {1434-6036}, doi = {10.1140/epjb/e2019-90672-2}, pages = {8}, abstract = {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.}, language = {en} } @misc{BorciaBorciaRichteretal., author = {Borcia, Ion-Dan and Borcia, Rodica and Richter, Sebastian and Xu, Wenchao and Bestehorn, Michael and Harlander, Uwe}, title = {Horizontal Faraday instability in a circular channel}, series = {Proceedings in Applied Mathematics and Mechanics (PAMM)}, volume = {19}, journal = {Proceedings in Applied Mathematics and Mechanics (PAMM)}, number = {1}, issn = {1617-7061}, doi = {10.1002/pamm.201900242}, pages = {2}, abstract = {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.}, language = {en} } @misc{BorciaBorciaXuetal., author = {Borcia, Ion-Dan and Borcia, Rodica and Xu, Wenchao and Bestehorn, Michael and Richter, Sebastian and Harlander, Uwe}, title = {Undular bores in a large circular channel}, series = {European Journal of Mechanics - B/Fluids}, volume = {79}, journal = {European Journal of Mechanics - B/Fluids}, issn = {0997-7546}, doi = {10.1016/j.euromechflu.2019.09.003}, pages = {67 -- 73}, abstract = {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.}, language = {en} } @misc{BorciaRichterBorciaetal., author = {Borcia, Ion-Dan and Richter, Sebastian and Borcia, Rodica and Sch{\"o}n, Franz-Theo and Harlander, Uwe and Bestehorn, Michael}, title = {Wave propagation in a circular channel: sloshing and resonance}, series = {The European Physical Journal Special Topics}, volume = {Vol. 232}, journal = {The European Physical Journal Special Topics}, number = {4}, issn = {1951-6401}, doi = {10.1140/epjs/s11734-023-00790-z}, pages = {461 -- 468}, abstract = {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}, language = {en} } @misc{BorciaBorciaBestehornetal., author = {Borcia, Rodica and Borcia, Ion-Dan and Bestehorn, Michael and Sharma, Deewakar and Amiroudine, Sakir}, title = {Phase field modeling in liquid binary mixtures: isothermal and non-isothermal problems}, series = {Physical Review Fluids}, volume = {7}, journal = {Physical Review Fluids}, number = {6}, issn = {2469-990X}, doi = {10.1103/PhysRevFluids.7.064005}, pages = {1 -- 19}, abstract = {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.}, language = {en} } @misc{BorciaPopescuBorcia, author = {Borcia, Rodica and Popescu, Sebastian and Borcia, Ion-Dan}, title = {IMA10: interfacial fluid dynamics and processes}, series = {European Physical Journal Special Topics}, volume = {232}, journal = {European Physical Journal Special Topics}, number = {4}, issn = {1951-6401}, doi = {10.1140/epjs/s11734-023-00798-5}, pages = {365 -- 366}, abstract = {MA10-special issue presents recent advances on interfacial fluid dynamics with applications in microfluidics, biology, engineering and geophysics.}, language = {en} } @misc{SchoenHarlanderBorciaetal., author = {Sch{\"o}n, Franz-Theo and Harlander, Uwe and Borcia, Ion Dan and Borcia, Rodica and Bestehorn, Michael}, title = {Mean fluid transport in an oscillating circular channel with asymmetric forcing}, series = {Water waves : an interdisciplinary journal}, volume = {2025}, journal = {Water waves : an interdisciplinary journal}, publisher = {Birkh{\"a}user, part of Springer Nature}, address = {Basel}, issn = {2523-3688}, doi = {10.1007/s42286-025-00121-w}, pages = {1 -- 21}, abstract = {We investigate surface waves in an oscillating circular channel with local topography. The focus is on spatially or temporally breaking this dynamic system's symmetry. Asymmetrical wave dynamics and a mean flux excitation are detected to varying degrees, depending on the two input parameters, fluid depth and the tank's oscillation frequency. The fluid resonates around multiples of the fundamental eigenfrequency of the channel. The development of solitary wave-trains (undular bores) is observed in these resonance bands. A particle image velocimetry system measures the velocity field in the vertical plane of the free surface flow. Moreover, we are using 17 evenly distributed ultrasonic sensors to measure the surface displacement. This makes it possible to find out how strongly the mean flux depends on the resonance frequencies and to study the influence of the surface waves on the symmetry breaking. A numerical long-wave model helps to isolate the various factors influencing the mean flux.}, language = {en} } @article{BorciaMerktBestehorn, author = {Borcia, Rodica and Merkt, Domnic and Bestehorn, Michael}, title = {A phase-field description of surface-tension-driven instability}, language = {en} } @article{BorciaBestehorn, author = {Borcia, Rodica and Bestehorn, Michael}, title = {Phase-field simulations for evaporation with convection in liquid-vapor systems}, series = {The European physical journal B}, volume = {44}, journal = {The European physical journal B}, number = {1}, issn = {1434-6028}, pages = {101 -- 108}, language = {en} } @article{BorciaBestehorn, author = {Borcia, Rodica and Bestehorn, Michael}, title = {Phase field models for Marangoni convection in planar layers}, language = {en} } @article{BorciaMerktBestehorn, author = {Borcia, Rodica and Merkt, Domnic and Bestehorn, Michael}, title = {Convective patterns in liquid-vaporsystems with diffuse interface}, language = {en} } @article{BorciaBestehorn, author = {Borcia, Rodica and Bestehorn, Michael}, title = {Phase field models and Marangoni flows}, language = {en} } @misc{BorciaBestehorn, author = {Borcia, Rodica and Bestehorn, Michael}, title = {Different behaviours of delayed fusion between drops with miscible liquids}, series = {Physical review E}, volume = {82}, journal = {Physical review E}, number = {3}, issn = {1063-651X}, pages = {036312}, language = {en} } @article{BorciaBestehorn, author = {Borcia, Rodica and Bestehorn, Michael}, title = {Phase field simulations for drops and bubbles}, language = {en} } @misc{BorciaBestehorn, author = {Borcia, Rodica and Bestehorn, Michael}, title = {Controlled Pattern Formation in Thin Liquid Layers}, language = {en} } @misc{BorciaBestehorn, author = {Borcia, Rodica and Bestehorn, Michael}, title = {A Phase Field Description of Spatio-Temporal Behavior in Thin Liquid Layers}, language = {en} } @article{BorciaBestehorn, author = {Borcia, Rodica and Bestehorn, Michael}, title = {Phase-field model for Marangoni convection in liquid-gas systems with deformable interface}, language = {en} } @misc{BorciaBestehorn, author = {Borcia, Rodica and Bestehorn, Michael}, title = {On the coalescence of sessile drops with miscible liquids}, series = {European Physical Journal E}, volume = {34}, journal = {European Physical Journal E}, number = {8}, issn = {1292-8941}, pages = {81}, language = {en} } @misc{BorciaMenzelBestehornetal., author = {Borcia, Rodica and Menzel, Stefan and Bestehorn, Michael and Karpitschka, Stefan and Riegler, Horst}, title = {Delayed coalescence of droplets with miscible liquids: Lubrication and phasefield theories}, series = {European Physical Journal E}, volume = {34}, journal = {European Physical Journal E}, number = {3}, issn = {1292-8941}, pages = {11024-9}, language = {en} } @misc{BorciaBestehorn, author = {Borcia, Rodica and Bestehorn, Michael}, title = {Numerical simulations on delayed coalescence of droplets in confinedgeometries}, language = {en} } @inproceedings{BorciaBestehornEgbers, author = {Borcia, Rodica and Bestehorn, Michael and Egbers, Christoph}, title = {Surface effects at the mixing of two perfectly miscible components in a thin liquid film}, series = {International Topical Team Workshop on Two-Phase Systems for Ground and Space Applications, ITTW 2013}, booktitle = {International Topical Team Workshop on Two-Phase Systems for Ground and Space Applications, ITTW 2013}, language = {en} } @misc{BorciaBestehorn, author = {Borcia, Rodica and Bestehorn, Michael}, title = {Partial coalescence of sessile drops with different miscible liquids}, series = {Langmuir}, volume = {29}, journal = {Langmuir}, number = {14}, issn = {1520-5827}, doi = {10.1021/la3050835}, pages = {4426 -- 4429}, abstract = {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.}, language = {en} } @misc{BorciaBestehorn, author = {Borcia, Rodica and Bestehorn, Michael}, title = {A phase field description of self-propulsion of twin sessile drops induced by surface tension gradients}, series = {Fluid Dynamics Research}, volume = {46}, journal = {Fluid Dynamics Research}, number = {4}, issn = {0169-5983}, doi = {10.1088/0169-5983/46/4/041405}, pages = {041405}, abstract = {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.}, language = {en} } @misc{BorciaBestehorn, author = {Borcia, Rodica and Bestehorn, Michael}, title = {Phase field modelling of non-equilibrium patterns on the surface of a liquid film under lateral oscillations at the substrate}, series = {International Journal of Bifurcation and Chaos}, volume = {24}, journal = {International Journal of Bifurcation and Chaos}, number = {9}, issn = {0218-1274}, doi = {10.1142/S0218127414501107}, pages = {1450110}, abstract = {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.}, language = {en} } @misc{BorciaBestehornUhligetal., author = {Borcia, Rodica and Bestehorn, Michael and Uhlig, Sebastian and Gaudet, Matthieu and Schenk, Harald}, title = {Liquid pumping induced by transverse forced vibrations of an elastic beam: A lubrication approach}, series = {Physical Review Fluids}, volume = {3}, journal = {Physical Review Fluids}, number = {8}, issn = {2469-990X}, doi = {10.1103/PhysRevFluids.3.084202}, abstract = {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.}, language = {en} } @misc{BestehornSharmaBorciaetal., author = {Bestehorn, Michael and Sharma, Deewakar and Borcia, Rodica and Amiroudine, Sakir}, title = {Faraday instability of binary miscible/immiscible fluids with phase field approach}, series = {Physical Review Fluids}, volume = {6}, journal = {Physical Review Fluids}, number = {6}, issn = {2469-990X}, doi = {10.1103/PhysRevFluids.6.064002}, pages = {1 -- 26}, abstract = {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.}, language = {en} }