Injection and Escape: A new model on the thrust generated by a thin pitching plate

We have proposed a physical model to describe the underlying physics behind the drag or thrust produced by a pitching panel in a uniform stream. Over the clockwise and counterclockwise pitching motions, the model categorizes Injection and Escape kinematic phases. The former estimates the total fluid volume gathered at the trailing edge, and the latter amount to the fluid volume fenced by the plate reaching the trailing edge. To verify our proposed model, we have performed three-dimensional simulations using an immersed boundary-based numerical code for the flow past a thin pitching plate at a Reynolds number of Re = 1000 for the aspect range of 0.54≤AR≤16 at maximum pitching angle of θmax=5°,15° with pitching frequency St=0.5,1. Our model reveals that the plate generates a net thrust in a pitching cycle when Injection dominates Escape and conversely for the drag cases.