The high-Re far wake of a slender body and the effects of density stratification

Abstract

The high-Reynolds-number wake of a slender body with a turbulent boundary layer is investigated using a hybrid simulation. The wake generator is a 6:1 prolate spheroid and the Reynolds number based on the diameter $D$ is $Re=10^5$. The transition of the unstratified wake to a state of complete self-similarity is investigated by looking for the first time into the far field of a slender body wake. Unlike bluff-body wakes, here the flow is not dominated by vortex shedding in the near wake. Instead, the recirculation region is very small, the near wake is quasi-parallel and is characterized by the presence of broadband turbulence. The simulations show that these particularities alter the decay rate of the wake significantly and challenge the notion of universality -- the idea that far from the body all turbulent wakes decay at the same rate. The influence of stratification in the wake is also studied at Froude numbers $Fr=U_{\infty }/ND=2$ and $10$. The results imply that the onset of buoyancy effects depends on the wake generator and that the far wake retains information of the initial conditions.

9 pages, 7 figures accepted in Symposium of Naval Hydrodynamics 2022