Numerical study of impeller-driven von Kármán flows via a volume penalization method

Abstract

The von Karman flow apparatus produces a highly turbulent flow inside a\ncylinder vessel driven by two counter-rotating impellers. Over more than two\ndecades, this experiment has become a very classic turbulence tool, studied for\na wide range of physical systems by many groups, with incompressible flow,\ncompressible flow, for magnetohydrodynamics and dynamo studies inside liquid\nmetal, for particle tracking purposes, and recently with turbulent super-fluid\nhelium. We present a direct numerical simulation (DNS) version the von Karman\nflow, forced by two rotating impellers. The cylinder geometry and the rotating\nobjects are modelled via a penalization method and implemented in a massive\nparallel pseudo-spectral Navier-Stokes solver. We choose a special\nconfiguration (TM28) of the impellers to be able to compare with set of water\nexperiments well documented. But our good comparison results implied, that our\nnumerical modelling could also be applied to many physical systems and\nconfigurations driven by the von Karman flow. The decomposition into poloidal,\ntoroidal components and the mean velocity fields from our simulations are in\nagreement with experimental results. We analyzed also the flow structure close\nto the impeller blades and found different vortex topologies.\n