Numerical study of pore-scale flow and noise of an open cell metal foam

Abstract

This paper studies numerically the three-dimensional pore-scale flow inside a single cell structure of an open cell metal foam and its aeroacoustic features. Since the Reynolds number based on the pore diameter is very low, the Navier–Stokes equations are solved directly to simulate the unsteady pore-scale flow. The permeability and pressure drop obtained from numerical simulations are compared with existing reference results. Numerical results reveal that the flow drag of the pore-scale structure is dominated by the pressure drag which is mainly caused by the flow separation, while the friction drag is much smaller than the pressure drag despite a very high surface area–volume ratio of the metal foam. The unsteady flow separation contributes primarily to the pressure drag and causes the self-noise of the metal foam, therefore suppressing the unsteady flow separation, e.g., by optimizing the cell structure of the metal foam, would reduce the drag and aerodynamic noise. The aeroacoustic features, such as noise sources, spectra and the directivity pattern, are investigated, and the results reveal a high correlation between the noise generation and the flow separation. The direction of the maximum sound pressure for the studied cell is parallel to the flow, which is different to flow separation from a cylinder where the direction of maximum radiation is perpendicular to the flow.

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