Lattice Boltzmann Simulations of Thermocapillary Convection in Self-rewetting Fluid Layers and Bubble Dynamics

Self-rewetting fluids (e.g., aqueous solutions of long-chain alcohols, certain liquid binary alloys, and nematic liquid crystals) exhibit anomalous nonlinear dependence of surface tension on temperature with a positive gradient. They involve significantly altered interfacial dynamics compared to ordinary fluids, which have recently been exploited in various applications. We will perform a computational study of thermocapillary convection in self-rewetting fluids in various configurations. To simulate such flows, we develop and utilize a robust central moment lattice Boltzmann (LB) method, which involve evolving three distribution functions; one to compute the fluid motion with attendant Marangoni stresses due to surface tension gradient, another one for interface tracking represented by the conservative Allen-Cahn equation, and finally, the third one to compute energy transport. First, thermocapillary convection in superimposed self-rewetting fluid layers in a microchannel driven by a periodic heating will be simulated and compared to newly developed analytical solution under creeping flow regime. Then, rising bubbles in self-rewetting fluids will be studied. Finally, the effect of anomalous surface tension behavior in mass transfer due to phase change will be presented.