Numerical study to investigate the viscous characteristic length on reconstructed porous media

Abstract

Until now, no general numerical method has been published for characterizing the viscous characteristic length, although there is a high demand to assist whole vehicle development with accurate geometric parameters. A new formula was proposed to determine the viscous characteristic length (Λ) directly based on the viscous dissipation work, which was combined with the general definition of the characteristic length. This new expression facilitated significantly faster convergence than the known formula (Johnson) for inviscid fluids by representing viscous fluids through the material sample. The complete CFD simulation procedure was introduced based on the solution of Navier-Stokes equations. The novel expression is capable of any homogeneous material samples assuming that high-resolution reconstruction can be carried out, compared to Johnson’s formula, which is limited to idealized cases. Good agreement between simulation and measurement results was found by applying fluid velocity instead of frequency. It was found that viscous losses dominate not only inside the pore connections but also in other regions, and the Reynolds number must be limited to the laminar regime. On that basis, the implemented model has more advantages against measurements and Johnson’s formula, like the repeatability as well as ensuring analyses under steady-state and real conditions.