Large-Eddy Simulation of Spatially Developing Turbulent Wake Flows

Abstract

The feasibility of applying the large-eddy simulation (LES) technique in complex high Reynolds number flows has been studied. The focus of the study is on the spatially developing wake flows with an application to ship wakes. The bluff body that generates the wake is excluded from the computational domain. To make this possible, a new random flow generation technique (RFG) is used to provide the turbulent inflow boundary conditions as a function of time. The technique provides an instantaneous velocity field at the inlet boundary in conjunction with the prescribed mean flow field obtained either from RANS (Reynolds averaged Navier-Stokes) simulations or from experimental data. The combined LES-RFG procedure has been validated in previous publications in cases of a flat plate and a mixing layer. At the inflow boundary, turbulence characteristics, including the shear stresses, were reconstructed. The time averaged results showed good agreement with the experiments in the developing wake. The same procedure is used to simulate a ship wake (ship model DTMB 5512) in the near field of 1.5 ship cord length. The LES technique captured both spatial and temporal development of the large coherent structures that play an important role in the evaluation of bubble concentration in the ship wakes. These structures are usually smeared out in RANS simulations.