Large eddy simulation of free-surface effects on the wake structures downstream of a spherical body

The wake structure downstream of a solid body, which moves near the free-surface, is under the influence of the free-surface motion. The rate of this influence depends on the submerging elevation or distance between the solid body and the free-surface. This investigation presents the interaction between the free-surface and the wake structure downstream of a spherical body at four different submerging elevations such as h/d=0.25, 0.50, 1.00 and 2.00 for the Reynolds number of 5000. For the present study, large eddy simulation (LES) using a dynamic Smagorinsky sub-grid stress (SGS) is applied on the hybrid grid system according to an advanced computer code based on the finite volume approach. Examination of obtained results reveals that the rate of interaction between the free-surface and the wake structure downstream of the spherical body is maximum for the case of h/d=0.25 and by increasing the submerging elevation, the rate of this interaction decreases. At the submerging elevation of h/d=2.00, the free-surface effects are minimum and beyond h/d=2.00 it may be assumed that these free-surface effects on the sphere wake structure disappear. (C) 2012 Elsevier Ltd. All rights reserved.