The Effect of Crossflow on Flapping Fins

Flapping fins can enable greater maneuverability in undersea vehicles. Most work to this point has only considered inflow perpendicular to the flapping stroke plane. However, this would not be true during maneuvers or while station keeping in a current. In this article, a simple model is presented which utilizes zero-crossflow data to predict the effect of crossflow on the forces produced by a flapping fin. This model compares well to experimental data taken over an array of crossflow and bias angles. The crossflow model may be useful for flapping fin vehicle simulations, feedforward models in vehicle controllers, and the development of a flapping fin controller that can compensate for inflow angle disturbances.