Automotive Aerodynamics Prediction using a Fast Transient Solver for Low-Mach Number Compressible Flow

This paper presents a fractional step time stepping scheme for low-Mach number compressible flow. The advantage of the proposed scheme compared to the iterative SIMPLEC is significant saving in computation effort while preserving secondorder accuracy. The proposed scheme and a transient SIMPLEC algorithm are verified and validated using a 2D convective isentropic vortex to qualitatively evaluate their convergence properties. Both schemes are stable at convective Co number equal one, and acoustic CFL greater than one. The L2 error norms of both schemes show second order accuracy, but the proposed scheme uses significantly less computation effort. Next, the aerodynamics of flow past a SAE 20 Notchback Model is predicted using the proposed scheme. Results of the SAE Model show good grid convergence, and good agreement in surface pressure coefficients with experimental measurement.