Suppressing the instability of impinging two-phase flow by anisotropic wetting strips

Abstract

This study investigates the effectiveness of anisotropic wetting strips in suppressing interfacial instability within a gas–water impinging system in a T-shaped microchannel. To accurately capture the high-speed interface dynamics, a modified dynamic contact angle model was implemented within the Open-source Field Operation and Manipulation framework. Numerical results indicate that the primary drivers of interfacial instability are intense pressure fluctuations and kinetic energy surges induced by the violent impinging of the gas and liquid phases. The findings demonstrate that introducing anisotropic strips with a pronounced wettability gradient is a highly effective method for enhancing interfacial stability. This wettability contrast generates a significant unbalanced Young's force at the strip boundaries, which serves as a robust anchoring mechanism to tightly pin the triple-phase contact line (TPCL). This pinning effect effectively suppresses the random oscillation and slippage of the TPCL, thereby stabilizing the global flow field. Furthermore, comparative analysis reveals that high-gradient anisotropic strips maintain a straight TPCL and a smooth, stable concave meniscus, whereas uniform surfaces or low-gradient strips result in chaotic interfacial deformations.