Predictions are reported of the two-dimensional turbulent flow around a square cylinder with rounded corners at high Reynolds numbers. The effects of rounded corners have proved difficult to predict with conventional turbulence closures, and hence, the adoption in this study of a two-equation closure that has been specifically adapted to account for the interactions between the organized mean-flow motions due to vortex shedding and the random motions due to turbulence. The computations were performed using OPENFOAM and were validated against the data from flows past cylinders with sharp corners. For the case of rounded corners, only the modified turbulence closure succeeded in capturing the consequences of the delayed flow separation manifested mainly in the reduction of the magnitude of the lift and drag forces relative to the sharp-edged case. These and other results presented here argue in favor of the use of the computationally more efficient unsteady Reynolds- averaged Navier-Stokes approach to this important class of flows provided that the effects of vortex shedding are properly accounted for in the turbulence closure.

We present experimental and computational results for the global drag force on a model Tension-Leg Platform (TLP) in uniform current for various values of the Reynolds number in the subcritical regime (Re = 104 - 1.06×105). The objective of the experiments, which were performed in a towing tank on a representative TLP configuration, was to provide data suitable for validating numerical model predictions. The purpose of the simulations was to determine the extent to which Large-Eddy Simulations (LES), when used as a truly predictive tool, can be relied upon to provide reliable estimates of the total drag force. Thus the simulations were performed only once with no further computations performed in order to bring about closer agreement with the measurements. The dependence of the computed results on the numerical grid was checked using the Grid-Convergence Index (GCI) method applied to results from benchmark flows. These results also served to assess the dependence on the value of the Smagorinsky constant in the model for the sub-grid scale terms. It was found that, at the highest value of Reynolds number considered, the variation between the measured and predicted values of the global drag coefficient was under 10% - a result which is in line with the limitations inherent in both.