76th Annual Meeting of the Division of Fluid Dynamics
Sunday–Tuesday, November 19–21, 2023;
Washington, DC
Session J38: Vortex Dynamics and Vortex Flows: Wakes II
4:35 PM–6:19 PM,
Sunday, November 19, 2023
Room: 204A
Chair: Prasoon Suchandra, Harvard University
Abstract: J38.00002 : Identifying Wake Structures Created by a Heaving and Flapping Foil Using a Bioinspired Hydrodynamic Sensory System*
4:48 PM–5:01 PM
Abstract
Presenter:
Gary A Glass
(University of Hawaii at Manoa)
Authors:
Gary A Glass
(University of Hawaii at Manoa)
Mike Krieg
(University of Hawaii at Manoa)
Fish can detect a vortex dipole created by the flapping of a neighbor's fin and coordinate schooling nearly instantaneously, using a sensory array called the lateral-line. We replicate these wake detection capabilities with a distributed sensory system inspired by the lateral-line. The engineered system consists of distributed pressure sensors, and the change in pressure over time is used to identify nearby fin wake patterns and determine the characteristics of the flapping fin such as the amplitude and frequency. Simultaneous Particle Image Velocimetry (PIV) measurements of the wake validate the results obtained by the sensors. Previous researchers have used PIV and other methods, such as dye visualizations, to observe the wake vortex structures created behind bluff bodies. Flapping fins have been observed to create wake patterns similar to the von Karman vortex street seen in the wake of bluff bodies. Previous studies have characterized how important parameters of the wake generation, such as the heaving amplitudes and frequencies, influence the types of wakes created. This study uses a custom designed mechanism with two DC motors to independently move the leading and trailing edge of an acrylic flat plate, creating any desired heaving and flapping motions, as it translates through a water tank. Adjusting the combination of heaving and flapping allows the creation of a wide range of wake types. The mechanism is suspended from a gantry system that runs the length of a 3.92m Long x 1.29m Wide x 1.07m High water tank. The gantry system is a Zaber LC40-KM02 Linear guide that can move the flapping mechanism at a maximum velocity of 0.5 m/s. Two NXP Semiconductor MPXV5000DP differential pressure sensors are used to determine wake characteristics such the horizontal and vertical spacing of the vortices as well the distance between each successive vortex. The wake parameters, which are validated using PIV, are correlated to flapping characteristics.
*Office of Naval Research; National Science Foundation