Modelling turbulent flow past a circular cylinder by RANS, URANS, LES and DES

Abstract

Incompressible turbulent flow past a circular cylinder is computationally investigated by a cascade of turbulence modelling strategies. Results are compared with experiments, by keeping the focus on the predictability of the drag coefficient. Two-Dimensional Reynolds Averaged Numerical Simulations (2D RANS) and Two-Dimensional Unsteady Reynolds Averaged Numerical Simulations (2D URANS) are performed for a wide range of Reynolds numbers, encompassing the critical regime. It is shown that the drag crisis can qualitatively be predicted by the 2D RANS, provided that the near-wall region is adequately resolved. The 2D RANS underpredicts the experimental drag coefficients for the most Reynolds numbers, seemingly due to the missing contribution of the organised transient motion. The 2D URANS, on the other hand, generally overpredict the drag coefficients, indicating the intimate relationship between the organised transience and three-dimensionality. Computations by three-dimensional transient procedures such as Three-Dimensional Unsteady Reynolds Averaged Simulations (3D URANS), Large Eddy Simulations (LES) and Detached Eddy Simulations (DES) are performed for the Reynolds number of 104. A substantial improvement in the prediction quality is observed. The best agreement with the experiments is obtained by the LES. The DES is also observed to deliver results that are very close to the measurements.