Similarity in the turbulent near wake of bluff bodies

Abstract

An experimental investigation has been carried out in the turbulent near wakes of several two-dimensional and axisymmetric bluff body models in the Reynolds number range of 1.13-5.0 x 10. For a 2-D wedge, the effect of varying the blockage ratio up to 25% has also been studied. Based on the locations of minimum pressure and maximum reverse velocity on the wake axis, characteristic length and velocity scales are suggested for both 2-D and axisymmetric near wakes. Using these scales, similarities in the distributions of static pressure and velocity defect are shown to exist for various models, including those with high blockage ratios. The dependence of these scales on model bluffness and blockage ratio is discussed. The difference between the near wakes of 2-D and axisymmetric bluff models appears as the opposite variations of the characteristic length scale and the length of the recirculation region with the minimum pressure coefficient. In the 2-D case these lengths decrease with the minimum pressure coefficient, while in the axisymmetric case they increase with it. A shielded hot wire is used for finding the length of the recirculation region.