Turbulence modulation and energy transfer in turbulent channel flow coupled with one-side porous media

The microscopic structure of porous walls modulates the turbulent flow above. The standard approach, the volume-averaged modelling of the porous wall, does not resolve the pore structure. To systematically link geometric characteristics with flow properites, direct numerical simulations are conducted which are fully-resolving the microscopic structure. A high-order spectral/hp element solver is adopted to solve the incompressible Navier-Stokes equations. Resolving the full energy-spectra relies on a zonal polynomial refinement based on a conforming mesh. A low and a high porosity case with in-line arrays of cylinders are analysed for two Reynolds numbers. The peak in the streamwise energy spectra is shifted towards the pore unit length for both cases. Proper Orthogonal Decomposition (POD) shows that the fluctuations in the porous wall are linked to the structures above. Q2 structures are linked with blowing events and Q4 structures with suction events in the first pore row. The numerical solver Nektar exhibits an excellent scalability up to 96k cores on "Hazel Hen" where a slightly improved performance is observed on the brand new HPE "Hawk" system. Strong scaling tests indicate an efficiency of 70 with around 5, 000 mesh-nodes per core, which indicates a high potential for an adequate use of a HPC platform to investigate turbulent flows above porous walls while resolving the pore structure.