Direct Numerical Simulations of Transitional/ Turbulent Wake of a Flat Plate

Abstract

The near wake of a flat plate with a circular trailing edge is investigated via direct numerical simulations. The boundary layers onboth the upper and lower surfaces toward the endof the plate are turbulent. Earlier experimental investigations have used thin plates with turbulent boundary layers to create the wake. This results in large =D values ( is the momentum thickness toward the end of the plate andD is the diameter of the trailing edge). Here the emphasis is on relatively thick plates with blunt trailing edges, which result in =D values less than unity. Such flows are of considerable engineering interest, particularly in turbomachinery. The computations are performed with a high-order accurate upwind-biased finite-difference scheme that has been successfully used in the past for direct numerical simulations of cylinder wakes and transitional/turbulent flow on flat plates and turbine airfoils. The simulation is modeled after an experiment. Both the Reynolds number based on the boundary-layer thickness at the end of the plate and ReD closely approximate experimental data. The ratio =D is about 0.05. Computed turbulence statistics both in the plate boundary layer and in the wake are compared with experimental data. Contours of the time-averaged and instantaneous velocity and vorticity fields in the wake are also provided and comparedwith those obtained for cylinder wakes.