A Computational Fluid Dynamics Methodology for Predicting Aeration in Wet Friction Clutches

Abstract

Computational fluid dynamics (CFD) has been unable to reliably predict aeration and drag torque in clutches. In this study, a CFD method was developed to reliably predict the onset of aeration and drag torque as a function of the clutch's rotational speed. This study showed that though the oil and air behave as if they are incompressible at steady-state, the formulation must account for the compressible nature of the gas and the unsteady processes that occur before reaching steady-state. This study also showed that the dynamic nature of the contact angle between the oil and the stationary disk must be accounted for to predict drag torque and aeration as a function of rotational speed, and a model of the dynamic-contact angle was developed.