An experimental investigation of a high Reynolds number turbulent wake generated by a vehicle-like bluff body*

Flow past bluff bodies is common in nature and has significant scientific and practical importance. The majority of goods transporters have bluff bodies, and the volume they must transport puts a limit on aerodynamic shape optimization. Owing to the adverse pressure gradient, the boundary layer developed on bluff bodies separates easily and creates a great deal of pressure drag. Oftentimes, these flows develop large-scale quasi-periodic structures, thus creating unsteady forces that affect the stability of the body itself. Despite being the subject of several basic studies, there aren't many experimental studies that completely charaterize each velocity component of a bluff body's turbulent wake at high Reynolds numbers. A study was conducted utilising stereo-particle image velocimetry (PIV) to fully characterise the wake of a vehicle-like bluff body at Reynolds number 3.43x10⁵ (defined as zU_∞/ν, where z is the spanwise width of the model (=514.3 mm), U_∞ is the free stream velocity, and ν is kinematic viscosity). Every instantaneous velocity component was measured at cross-stream planes (with a resolution of 1 mm²) at different streamwise locations (100 mm apart), starting from the trailing edge of the model. The flow is visualized, and the basic features are extracted (e.g., the separation bubble, corner vortices) and characterized using different techniques (e.g., Singular Value  Decomposition). The effect of these structures on the unsteady forcing on the body is discussed, and comments are made on possible control scenarios. This work was supported by the EPSRC (Grant No. EP/W009935/1).