Development of underwater stereo-PIV systems for the characterization of high Reynolds number separated flow around a 6:1 prolate spheroid

The presence of three-dimensional boundary layers, pressure gradients, and open separation poses a considerable challenge for turbulence models, particularly when it comes to prediction of dynamic loading on the bodies that generate such flows. This difficulty is due in large part to incomplete understanding of the mechanisms responsible for the onset and sustainment of separation. As such, measurements of both the near-wall and separated regions of a representative flow offer the potential to advance modeling capability for this important class of flows. To this end, we describe the development of several submersible stereo-PIV systems designed to characterize the flow around a 3 meter chord length 6:1 prolate spheroid across a range of attack angles. One such system is to be contained within the model itself and will target the near-wall flow and wall shear stress, while the other will be mounted downstream and will target the lee side wake. Discussion of the internal system includes a strategy for imaging the flow through the curved wall of the body, a consideration necessitated by the differing refractive indices of common viewing window materials and the flow medium.