ASSESSMENT OF PRECONDITIONING METHODS FOR MULTIDIMENSIONAL AERODYNAMICS

We consider the steady state equations for a compressible fluid. For l ow speed flow the system is stiff since the ratio of the convective sp eed to the speed of sound is very small. To overcome this difficulty w e alter the time dependency of the equations while retaining the same steady state operator. In order to achieve high numerical resolution w e also alter the artificial dissipation (or Roe matrix) of the numeric al scheme. The definition of preconditioners and artificial dissipatio n terms can be formulated conveniently by using other sets of dependen t variables rather than the conservation variables. The effects of dif ferent preconditioners, artificial dissipation and grid density on acc uracy and convergence to the steady state of the numerical solutions a re presented in detail. The numerical results obtained for inviscid an d viscous two-and three-dimensional flows over external aerodynamic bo dies indicate that efficient multigrid computations of flows with very low Mach numbers are now possible. (C) 1997 Elsevier Science Ltd.