A Matrix-Free Implicit Method for Flows at All Speeds

Matrix-free implicit treatments are now commonly used for computing compressible flow problems: a reduced cost per iteration and low memory requirements are their most attractive features. This paper explains how it is possible to preserve these features for all-speed flows, in spite of the use of a low-Mach preconditioning matrix. The proposed approach exploits a particular property of a widely used low-Mach preconditioner proposed by Turkel. Its efficiency is demonstrated on some steady and unsteady applications.