A comparative analysis of clapping propulsion in stationary and freely moving conditions

In aquatic habitats, pulse-jet type of propulsion can be observed, for example, in jellyfish and squid. In the present study, pulse jet propulsion is studied with a system consisting of two thin flat plates that clap together. We consider two cases: the body is free to move and the other in which the body is fixed.

In the stationary case, the angular velocity of the plate is lower than that in the freely moving case. In both cases, a pair of counter-rotating vortices are formed. However, there are quantitative differences in the two flow fields and ejected fluid masses, as revealed by the PIV measurements in two mutually perpendicular planes. In the freely moving case, we study the relationship between body motion and wake flow.