Flow Transition Behavior between the Liquid Film Flow and the Liquid Rivulet Flow on an Inclined Plate

Abstract

Gas-liquid interfacial flows, such as liquid film flows (also known as wetting flows on plates), are encountered in many industrial processes including absorption, distillation and so on. The present study focuses on detailed descriptions of the flow transition phenomena between the film flow and the rivulet flow, as well as how such phenomena are affected by wall surface texture treatments.This study develops a numerical simulation technique using Computational Fluid Dynamics (CFD) with the Volume of Fluid (VOF) model as well as a lab-scale experimental testing technique. As the liquid flow rate is increased and then decreased, a hysteresis of the transition between the film flow and the rivulet flow is discovered, which implies that the transition phenomenon depends primarily on the history of the change of interfacial surface shape. Further study on the effect of texture geometry shows quantitatively that surface texture treatments added on the plate can help to prevent the liquid channeling and can increase the wetted area. The main reason for increasing the wetted area on the wavy surface is that the liquid film break-up is inhibited due to the liquid holding on the plate and the spreading of the liquid flow in spanwise direction by the wavy surface geometry. Additionally, the simulation results agree well with the experimental results in terms of the gas-liquid interfacial surface shape and the wetted area in the transition region between the film flow and the rivulet flow.