Meeting Abstract
Unsteady aquatic maneuvers, including the rapid starts and jumps performed by fish, are highly three-dimensional events. The interactions between multiple fins and the body generate complex flow structures that need to be resolved simultaneously across varying time and length scales in order to gain a full picture of the resulting hydrodynamics. This work focuses on fully time-resolved, three-dimensional velocimetry during rapid maneuvers, prey capture, and jumping events. These events cannot be studied in a flume, as the organism must be allowed to move freely in a quiescent tank. Resultantly, the body kinematics and wake structures tend not to align with laboratory-centric reference frames and rectilinear measurement techniques such as planar Particle Image Velocimetry (PIV). Velocity fields must be analyzed with geometry-flexible frameworks and without the classical assumptions made in 2D PIV when quantifying swimming momentum and unsteady forces.
Light field imaging techniques and Synthetic Aperture PIV enable time-resolved volumetric measurements which, combined with advanced flow feature identification algorithms, are necessary to quantitatively analyze such behaviors and extract accurate 3D force measurements on the fish. We present results obtained from fully time-resolved volumetric PIV on maneuvering Giant Danio (Devario aequippinatus), as well as canonical round vortex rings, which are the underlying propulsive mechanism in rapid maneuvers. We consider the influences of limited spatial resolution, flow feature identification for arbitrary geometries, and body reconstruction uncertainty on the measurement. Recommendations are made for a general procedure for propulsion analysis from 3D PIV data, regardless of which velocimetry technique was used to obtain the velocity fields.
