Propulsive performance from oscillating propulsors with spanwise flexibility

The propulsive performance of oscillating foils with spanwise flexibility was studied using a time-domain panel method. The work was done to assess the effects of spanwise flexibility on the propulsive efficiency of these propulsors, especially those employed by relatively fast swimming marine animals. The method is valid for three-dimensional attached flows around the actual planforms found on these animals and was used in the study reported here to assess the performance of the flukes of an immature fin whale (Balaenoptera physalus). It is shown that passive spanwise flexibility reduces propulsive efficiency, but that propulsive efficiency of these planforms can be increased, over the value for an equivalent rigid foil, by careful control of the phase of the spanwise flexibility relative to other motion parameters.