Meeting Abstract

80.5  Monday, Jan. 6 11:15  Can larval fish enhance their hydrodynamic performance of backward C-starts by capturing their own wake? LI, G.*; MULLER, U.K.; VAN LEEUWEN, J.L.; LIU, H.; Chiba University; California State University Fresno; Wageningen University; Chiba University dr.mango@icloud.com

Fish can sense and capture the wakes of other fishes to achieve better hydrodynamic performance. In this study, we explore whether fish are also capable to enhance hydrodynamic performance by capturing their own wake when the body bends with a sufficiently large curvature as occurs during extreme ‘backward C-starts’. We examined the extremely fast backward C-start maneuver of zebrafish larva. So far, the flow field of such maneuvers has not been measured directly. Recently, however, we have developed an integrated computational approach by coupling the equations of body dynamics and hydrodynamics to simulate a free-swimming larval zebrafish. We validated our model through a careful comparison of both flow patterns and body kinematics with experimental observations, which showed a reasonable agreement. We further conducted a series of simulations to explore the mechanism of forward and backward C-starts, including the performance of maneuvers, as well as their correlations with the simulated flow patterns.Our numerical simulations suggest that a wake capture mechanism in larval fish occurs during the backward C-start: when the fish ends the preparatory stroke, it almost accomplishes the backward turning with the body curved into an approximate circle and the wake shedding from the tail and occasionally sweeping over the fish’s snout. During the subsequent propulsive stroke, the larva apparently follows the shed jet while absorbing it into its own boundary layer. By exploiting this jet-momentum flowing around the snout, the fish presumably enhances its hydrodynamic performance.