DNS/LES Studies of Turbulent Flows Based on the Cumulant Lattice Boltzmann Approach

In many industrial and environmental problems we encounter turbulent flows over porous surfaces which also penetrate the porous medium to different extents. Although there is a wealth of literature on macroscopic models of such phenomena which do not take the pore scale explicitly into account, these approaches typically require some additional transport coefficients to match experimentally obtained statistics for mass, momentum and energy transport across such interfaces. In this project we conduct Direct Navier-Stokes (DNS) and Large Eddy Simulation (LES) computations of turbulent flows which explicitly take into account specific pore scale geometries obtained from computer tomography imaging and do not use any explicit turbulence modeling. In this first part of the project we conducted validation studies for two canonical turbulent flows, i.e. flow around a plate and flow in a porous channel. Subsequently, we compare simulation results of turbulent flows over a porous sand and to experimental results and demonstrate the validity of our approach. Finally we discuss our approach to address evaporation processes on a pore scale which is based on a separation of time-scales. The newly developed cumulant Lattice Boltzmann scheme implemented as part of our research Code VirtualFluids shows a favorable behavior with respect to parallelization efficiency as well as to numerical stability and accuracy.