Evolution of Gas Film and Corresponding Drag Reduction Performance in Microchannels with Multi-Configuration Wall...

The presence of a gas film at the solid-liquid interface can effectively reduce fluid flow resistance. This study utilizes numerical simulations to explore how groove microstructures on the lower wall of microchannels affect the evolution of trapped bubbles into gas films, as well as the resultant fluid flow behaviors inside microchannels. The influences of groove number, groove shape and double-layer microstructures on gas film formation and fluid boundary slip length are analyzed in detail. The results show that increasing the groove number can significantly improve the continuity and stability of the gas film. Groove shape also has a prominent effect on the evolution of bubbles and gas films. With the longest spreading length of gas film, rectangular grooves present a slip length about 23.9% higher than that of triangular grooves. Simultaneously, it was discovered that bilayer microstructures, especially in cases with smaller periods, can notably enhance the spreading speed, length and thickness of gas film. This improvement, in turn, further increases the slip length and boosts the drag reduction effect. This work highlights that rational optimization of wall microstructures in superhydrophobic microchannels facilitates the generation of stable, continuous gas films, yields a prominent enhancement in slip length, and consequently achieves efficient drag reduction in microfluidic systems. The present findings offer valuable fundamental understanding and technical guidance for the structural design of advanced microfluidic devices.