On the turbulent flow past a realistic open-cell metal foam

Abstract

Turbulence is investigated in the lee of an open-cell metal foam layer. In contrast to canonical grids metal foams are locally irregular but statistically isotropic. The solid matrix is characterised by two lengths the ligament thickness and the pore diameter. A direct numerical simulation is conducted on a realistic metal foam geometry for which and the porous layer thickness is five times the pore diameter. The Reynolds number based on the pore size is corresponding to a Taylor-scale Reynolds number. Closer to the foam than two pore diameters the pressure and turbulent transports of turbulent kinetic energy are non-negligible. In the same region undergoes a steep decrease whereas the dissipation coefficient increases like. At larger distances from the porous layer the classical grid turbulence situation is recovered where the mean advection of turbulent kinetic energy equals dissipation. This entails a power-law decay of turbulent quantities and characteristic lengths. The decaying exponents of integral Taylor and Kolmogorov scales are close to one-half indicating that the turbulence simulated here differs from Saffman turbulence. Analysis of the scaling exponents of structure functions and the decorrelation length of dissipation reveals that small-scale fluctuations are weakly intermittent.