Direct Numerical Simulation (dns) of Turbulent Flow over Wavy Surfaces

Abstract. The present study adresses the turbulent flow over a wavy surface by direct numerical simulation (DNS). Compared to classical channel flow the wavy surface structure adds a degree of complexity to the flow by inducing streamline curvature, flow separation and flow reattachment, thus leading to flow situations which are often present in relevant technical and geophysical applications. The governing equations are discretized with a second order finite volume method on Cartesian, structured, staggered grids, and are integrated in time using the semi-implicit projection method. The wavy surface is represented with a variant of the immersed boundary method (IBM). The solution of the discretized system of linear equations is accelerated with an algebraic multigrid procedure. The simulations were performed on the Cray XT5 computer and scale well up to 128 processors. The flow over the wavy surface is particularly challenging for the IBM since the cells are cut at different angles in the regions where the most interesting phenomena like separation and reattachment takes place. In the present work, particular attention was payed on the size of the computational domain, ensuring it does not hinder the natural development of coherent structures in the considered flow. The results of the simulations compare favorably with particle image velocimetry (PIV) measurements, showing the IBM is an interesting candidate for simulating flows over wavy surfaces.