Experimental study of the flow structure around the oral arms of a jellyfish-inspired pump mechanism

Abstract

To mitigate microplastic and suspended solid debris problems, various underwater debris-collecting devices have been proposed; however, due to concerns regarding blockage in these devices’ suction pumps, simple-structured pumps with high robustness are more suitable for long-term operation. Thus, we previously proposed a debris-capturing pump mechanism inspired by the jellyfish of the Rhizostomeae order’s simple anatomy, focusing on the flow around the oral arms, which is expected to greatly affect debris-collecting performance. In the current study, the vertically integrated two-dimensional jellyfish-inspired pump’s bell material and the installment angle of the rectifier plates mimicking the oral arms were varied across four configurations, and the flow fields generated by the pump with their governing dominant flow structures were investigated using particle image velocimetry (PIV) and proper orthogonal decomposition (POD) to evaluate the effect of both variables on the flow structure. Experimental results suggest that both variables affect the flow structure and reverse flow rate significantly. By increasing the bell’s elastic modulus and installing the plates at a moderate angle, the reverse flow in the bell-opening motion can be suppressed.