Conventional time marching flow solvers perform poorly when integrating compressible flow equations at low Mach numbers levels. This is shown to be due to unfavourable interaction between long wavelength errors and the inflow and outflow boundaries. Chorin’s method of artificial compressibility is adopted to extend the range of Denton’s inviscid flow solver and Dawes’ three-dimensional Navier-Stokes solver to zero Mach number flows. The paper makes a new contribution by showing how to systematically choose the artificial acoustic speed to optimize convergence rate with regard to the error wave-boundary interactions. Applications to a turbine rotor and generic water pump geometry are presented.

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