A Global Preconditioner for Viscous Flow Simulations at All Mach Numbers

Kidambi Sreenivas, Lafayette K. Taylor and W. Roger Briley
The University of Tennessee at Chattanooga, Chattanooga, Tennessee, 37403

An iterative implicit algorithm based on a constant global preconditioner is developed for the Reynolds-averaged Navier-Stokes equations at arbitrary Mach number. This algorithm employs a primitive-variable Roe flux-difference approximation. Two choices of primitive variables are considered, i.e., pressure, velocity and temperature or pressure coefficient, velocity and temperature. The use of the latter variable set results in the virtual elimination of roundoff error at low Mach numbers and a Mach number independent convergence rate is demonstrated on a realistic geometry. Results are presented that show the applicability of the flow solver to low speed (Mach number ~ 0.0) as well as high speed (Mach number > 1) flows. Results include comparisons between solutions obtained using the current algorithm with a compressible solver (for high speed cases) and experimental data.