Primary Prediction of Oil Film Cavitation Between Rotating Friction Pairs with Various Types of Surface Textures

Oil film cavitation in the friction pairs of wet clutches significantly compromises transmission stability and component durability. This study investigates the cavitation evolution across three microtexture types—hexahedral, cylindrical, and hemispherical—with texture ratios ranging from 3.205% to 12.917% and a constant depth of 0.0564 mm, under a 6000 rpm operating condition. A finite element model of the oil film was established to analyze the cavitation volume fraction, pressure field, and gas-phase mass transfer rate. The numerical simulations were complemented by visualization experiments, where high-speed imaging (550–1050 rpm) captured the cavitation bubble dynamics, and the transmitted torque was measured. The results indicate that microtexture parameters profoundly influence cavitation intensity. Hemispherical textures with a 6.41% texture ratio yielded the highest cavitation volume fraction (0.020215), substantially exceeding that of hexahedral textures (0.0015197). Cavitation initiates within the texture dimples, with hemispherical geometries facilitating its diffusion into non-textured regions. A threshold effect of the texture ratio was identified, where cavitation intensity peaks at 6.41% but diminishes at 12.917%, attributable to flow homogenization. Optimized designs can effectively suppress cavitation: either increasing the texture depth or adopting a high texture ratio (>45%) with hexahedral or cylindrical geometries reduces the pressure drop in low-pressure zones by over 30%. Experimental validation confirmed that an increased texture ratio reduces torque by 20%, correlating with the shrinkage of the oil film at the outer diameter. High-speed imaging revealed a periodic cavitation evolution, with the collapse of sheet-to-cloud cavitation occupying 15.2% of the cycle, which aligns with the simulated peak in mass transfer at t = 0.003 s. In conclusion, cavitation can be effectively controlled by optimizing the texture ratio, depth, and geometry to maintain a stable oil film pressure gradient. This study provides a theoretical foundation for the microtexture design of wet clutches, thereby enhancing their reliability in power-shift applications.