An Investigation of Bio-Inspired Hydrodynamic Performance Through the Analysis of the Wake Structures Behind a Pitching Plate

Abstract

In the study of fluid dynamics, the wake structures produced by a body moving in a fluid provide both a visualization of the flow and an explanation for the resulting flow properties of the wake. This research used an immersed boundary projection method (IBPM) to conduct direct numerical simulations to examine the wake structures produced by a sinusoidally pitching plate. The wake structures were studied over a range of dimensionless amplitudes and reduced frequencies of the pitching motion and four different structures were found. In one case, the wake did not develop any coherent vortex structures. Two of the wakes were structures that have been frequently observed by similar studies: a 2S wake and a P + S wake. The fourth structure found was a unique variation on these wakes, designated by P + C, that is characterized by a set of co-rotating vortices trailing after a counter-rotating vortex pair. The fluid dynamic properties of the wake structures were also studied to analyze the drag produced over the body. The flow within the parameter region that produced the minimum average drag coefficient occurred at the beginning of the wake transition from the 2S wake to the P + S wake. Further study could be conducted to explore more details of the fluid dynamics of these parameters, to examine the transitions between the different wake structures in the parameter space, and to use this study as a foundation for research into more complex geometries and kinematics that have a strong connection to biological propulsion.