CFD-Based Parametric Optimization of Friction Pad Geometry for Drag Torque Reduction in a Wet Clutch

In this study, we numerically investigated the effect of friction pad geometry on drag torque reduction in the disengaged state of a wet clutch used in an integrated mechanical limited-slip differential (mLSD)-disconnector module. A paper-based friction pad was considered, and three-dimensional computational fluid dynamics (CFD) simulations were performed for a periodic sector using ANSYS Fluent 2021 R1 under oil-filled single-phase conditions. The numerical approach was validated against previously reported numerical results, showing an average deviation in dimensionless drag torque of less than 0.5%. The effects of friction pad geometry on lubricant flow behavior, wall shear stress, and drag torque were then evaluated. Based on these results, full factorial combination analysis and piecewise cubic Hermite interpolating polynomial (PCHIP) methods were applied to derive an optimized groove geometry that reduces drag torque while limiting the reduction in friction pad area. The selected PCHIP-based geometry reduced drag torque by approximately 4.10% relative to the reference geometry while limiting the friction pad area loss to within 2.50%. These results show that drag torque can be reduced by forming an effective oil discharge path through appropriate groove geometry design, providing a practical CFD-based optimization approach for improving wet clutch efficiency while maintaining the effective friction pad area.