Computation of turbulent vortex shedding

Abstract

The paper reports on the prediction of the flow field around smooth cylinders in cross flow at high Reynolds number. Both circular and square-sectioned cylinders are considered. The principal feature of these flows, and the primary cause for the difficulty in their prediction, is the development of a von Karman vortex street leading to significant fluctuations in surface pressures. It has already been established from several previous studies that eddy-viscosity closures fail to capture the correct magnitude of these fluctuations though there is no consensus as to the underlying causes. In this work, it is argued that the organized fluctuations in the mean-flow field introduce energy into the random turbulence motions at a frequency that corresponds exactly to the shedding frequency and that, as a consequence, it becomes necessary to explicitly account in the turbulence closure for the resulting modification of the spectral transfer process. A proposal to account for this direct energy transfer in the context of two-equation eddy-viscosity closures is put forward and is checked by comparisons with experimental data from both square and circular cylinders at high Reynolds number. Uncertainties in the predictions due to numerical discretization errors are systematically minimized. The outcome of comparisons with experimental data and with results from alternative closures, including Large-Eddy Simulations, validate the proposal.