Aeroacoustic modelling of low-speed flows

A new numerical algorithm for acoustic noise generation is developed. The a pproach involves two steps comprising an incompressible flow part and an in viscid acoustic part. The acoustic part can be started at any time of the i ncompressible computation. The formulation can be applied both for isentrop ic flows and non-isentropic flows. The model is validated for the cases of an isentropic pulsating sphere and non-isentropic flows past a circular cyl inder. In the latter case the computations show that the generated acoustic field in addition to the dominant Strouhal frequency, f(0), contains a sli ghtly higher frequency, f(2), and a modulating lower frequency, f(1) = f(2) - f(0). Numerical experiments with different interpolation schemes, bounda ry conditions, etc., show that the appearance of these modes is not an arti fact from the numerical discretization.