Numerical simulation of the transient flow behaviour in chemical reactors using a penalisation method

We present a numerical scheme to study the transient flow behaviour in complex geometries. The Navier-Stokes equations are discretized with a high-resolution Fourier pseudo-spectral discretization with adaptive time-stepping. Using a penalisation technique solid boundaries of arbitrary shape can be easily taken into account. As application we present different simulations of unsteady flows, typically encountered in chemical reactors. We study transitional flows in tube bundles (arrays of cylinders and squares) for different Reynolds numbers and angles of incidence and a channel flow with an obstacle.