Effect of Reynolds number and model chord on the wake structure of a blunt trailing edge profiled body

The near wake of a bluff body, and in particular the vortex street, is closely associated with the mean and fluctuating forces experienced by the body. A blunt trailing edge (BTE) profiled body geometry is the focus of the present study. Despite the spanwise uniformity of the BTE body itself, its wake is highly three-dimensional once it transitions to turbulence. At large scales, this three-dimensionality manifests as oblique shedding and vortex dislocations, which tend to modulate the aerodynamic forces. The effect of Re and model chord length, c, on the three-dimensional wake structure is experimentally investigated using a combination of hot-wire anemometry and particle image velocimetry (PIV) measurements. All the cases in the 2,800 < Re < 36,000 range investigated in this study have a turbulent wake. An important distinction is made in this study between Re > 11,000 cases, where the boundary layer transitions upstream of the trailing edge and lower Re cases where the boundary layer is laminar over the body and transitions in the wake. The wake velocity field is shown to be much less correlated for the former case. Furthermore, in the laminar boundary layer regime the spanwise correlation drops as Re increases due to the growth in the magnitude of the velocity fluctuations in the separated shear layers. As the thickness of a turbulent boundary layer increases, the strength of the shed vortices decreases and the ratio between the velocity fluctuations in the shear layers to the shedding strength increases. Consequently, we find that the spanwise correlation drops as the thickness of a turbulent boundary layer increases. The changes in the spanwise correlation is fopund to be related to the spanwise phase drift of the vortex shedding and the incidence of dislocations.