Investigation of hydrodynamic instabilities at the two-phase interface of falling film using the multipseudopotential interaction lattice Boltzmann method.

Abstract

In the present study, the lattice Boltzmann method coupled with the multipseudopotential interaction interparticle force model is employed to investigate the vertical falling film phenomenon. Utilization of this method enables the presentation of various study cases and the adjustment of dimensionless Reynolds and Kapitza numbers within the range of 5.1<Re<35 and 14<Ka<85 simultaneously with reduced computational costs. Waves are induced by sinusoidal excitation at the inlet, and the domain length is chosen to ensure the development of fully developed waves. Numerical results pertaining to wave peak thickness, wave trough thickness, and wave speed are compared with experimental results, which exhibit good agreement. Influential factors affecting velocity profile deviation within waves from the semiparabolic state, including wavy regime and the presence of capillary ripples, are investigated. The current numerical model has the capability to observe vortices resulting from the recirculation phenomenon at the wave peak and can concurrently model flow conditions regarding negative shear stress and proximity to flow reversal in line with experimental findings. Wave peak height and flow rate at Ka=25 are studied as functions of Reynolds number variations, revealing that at the second critical Reynolds number equal to 25, the wave peak height and maximum flow rate reach their highest values, coinciding with the occurrence of the recirculation phenomenon.