Collisions of localized convection structures in binary fluid mixtures

Abstract

Abstract. Collisions of a localized traveling wave structure with a localized stationary structure are investigated. In ethanol-water mixtures with appropriately chosen negative separation ratios, both exist bistably in the unstable quiescent surrounding for a range of supercritical heating rates. Depending on the Rayleigh number, we observe different evolution scenarios of the convection structures that appear as a result of the collision. The incident localized traveling wave can be absorbed by the stationary structure and then the latter expands: either both of its fronts get unpinned and propagate into the quiescent fluid or only the one that is hit propagates while the opposing one remains pinned. For smaller Rayleigh numbers, the stationary structure is destroyed while the incident localized traveling wave survives and a second one is created that moves ahead of the incoming one, both being coupled together. The mechanisms involved in these scenarios are analyzed and elucidated with the help of finite difference numerical simulations that are carried out subject to realistic boundary conditions.

Travelling convectons in binary fluid convection

“…These localized states consist of travelling waves under a stationary or slowly drifting envelope (Kolodner et al 1989;Steinberg et al 1989;Surko et al 1991;Barten et al 1995). States of this type can also undergo collisions (Kolodner 1991b;Iima & Nishiura 2009;Taraut, Smorodin & Lücke 2012;Watanabe et al 2012) but are quite different from the drifting localized states studied here which are time-independent in the moving frame.…”

Localized structures in convective experiments

“…Strong movements destroy the concentration effects. The role played by the concentration field, among others analysis, can be found in references [30][31][32][33][34].…”

Traveling-Wave Convection with Periodic Source Defects in Binary Fluid Mixtures with Strong Soret Effect

“…Laboratory experiments have observed convective states taking the form of traveling waves (TW) [ 2 ], localized TW (LTW) [ 3 , 4 ], stationary overturning convection (SOC) [ 2 ], blinking [ 5 , 6 ], counterpropagating waves (CPW, or “chevrons”) [ 7 , 8 ], repeated transients [ 7 , 8 ] and dispersive chaos [ 9 ]. After these pioneering studies, many research by direct numerical simulations (DNS) were conducted to further understand and identify the mechanisms of the convective states, see e.g., References [ 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 ]. By DNS one can get easily the values at any point of the flow fields and extract from them information difficult or impossible to obtain in the experiments, this allows a better understanding of the convective states.…”

“…For low Rayleigh numbers, it is also challenging to investigate the problem by 3D simulations for a broad range of control parameters. Two-dimensional (2D) simulation, which is substantially less computational cost and found to capture many essential features of 3D convection [ 30 , 31 ], is a useful tool in fundamental research and has been widely used to study Rayleigh–Bénard convection, not only in binary fluids [ 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 ] but also in one-component fluid [ 28 , 29 , 32 , 33 ]. Barten and his coworkers [ 10 ] first reported the DNS results of convection in water-ethanol mixtures with separation ratio , and then studied in detail the TW and SOC states in binary mixtures with different values in a narrow container of a single wavelength [ 11 ].…”

“…localized SOC (LSOC, or so-called “convectons") in the He- He mixtures for the first time [ 34 ], and found that this state also exists in water-ethanol mixtures [ 15 ]. After that, multiple LSOC states such as anticonvectons, wall-attached convectons and stable traveling convectons, and collisions between different localized states were studied by different groups [ 16 , 17 , 18 , 19 ]. Recently, Smorodin et al [ 20 ] discussed the influence of high-frequency transversal vibrations on the convective instability and pattern formation, and found that the unstable weakly nonlinear TW regime can be stabilized by means of high-frequency vibrations.…”