Computational Investigation of Multiple Oscillating Hydrofoils and its Effect on Thrust Augmentation

Abstract

Previous investigations of flapping hydrofoils for the purpose of thrust production have been limited to one or two in tandem. Tandem foils were found to have superior performance because the performance of the aft foil was augmented by the vortices shed from the fore foil. It is however not clear if increasing the number of foils will continue to have increased performance or if there exist an optimal number after which the overall performance either stagnates or reduces. A 2D computational study was conducted to investigate the effect of increasing the number of hydrofoils to four at a Reynolds number of 8000 flapping in-phase and out-of-phase. Optimal and sub-optimal conditions found previously with tandem hydrofoils were found also be applicable to three and four hydrofoils.