Wake topology and dynamics over a slender body at a high incidence and their relation to structural loading

Abstract

The flow over a slender cylindrical body with a hemisphere end was studied experimentally using a combination of force balance and time-resolved particle image velocity measurements. The investigation was performed at a subcritical Reynolds number (Re = 11 000) over a range of high incidence angles from 30° to 90°. The results show that significant cross-flow loading occurs for a range of incidence angles from 50° to 70°, with maximum mean and fluctuating loads taking place at 60°. Within this range of incidence angles, the loading has a bimodal nature, with intermittent switching between two states associated with the positive and negative cross-flow loading direction. The analysis of simultaneous force and wake measurements reveals that the two loading regimes are produced by two distinct wake topologies defined by strongly asymmetric vortex dynamics near the tip of the model. The results provide insight into salient features of the wake development and vortex dynamics and show that transient changes in the cross-flow force direction progress through a consistent change in the wake structure between two bounding quasi-steady states.