Transient experimental analysis in the wake of bluff bodies

The study of the flow around bodies that do not have an aerodynamic profile, called bluff bodies, is a challenge in fluid mechanics, mainly, if these bodies are arranged in a tandem set up. This paper deals with a tandem configuration with a cylinder placed inside the wake of a prism in two distinct arrangements, the first with the frontal face of the prism aligned 90 degrees to the flow and the second with the frontal face of the prism aligned 45 degrees to the incoming flow. Initially, the flow features caused by the flow detachment and boundary-layer interactions were qualitatively identified by flow visualization paint of the shear stresses over the flat plate where the models were mounted. Then, PIV experiments were conducted to measure and analyze the mean vorticity fields and velocity vectors on horizontal and vertical planes of the prism and cylinder wakes. To better quantify these observations, measurements with constant temperature hot-wire anemometry were also conducted to explore velocity field statistics and turbulence properties of turbulent wake regions. A comparison between the tandem configuration and the isolated cylinder case was conducted, and it was observed that the tandem configuration presented higher levels of turbulence intensity when compared to the isolated cylinder. In addition, the measurements showed that the prism wake influences that of the cylinder, although, regarding macro and microscale turbulent structures, this influence is only noticed in positions above the half height of the cylinder body. The results show that the impact of the tandem configuration on the flow around the cylinder is mainly driven by the downwash three-dimensional effect originated by the prism wake.