Abstract
Inspired by a previous experimental study of fish swimming near a cylinder, we numerically investigate the swimming and station-holding behavior of a flexible plate ahead of a circular cylinder whose motion is controlled by a proportional–derivative (PD) controller. Specifically, the deformation of this two-dimensional plate is actuated by a periodically varying external force applied on the body surface, which mimics the fish muscle force to produce propulsive thrust. The actuation force amplitude is dynamically adjusted by a feedback controller to instruct the plate to swim the desired distance from an initial position to a target location and then hold the station there. Instead of directly using the instantaneous position signal, an average speed measured over one force actuation period is proposed with the inclusion of instantaneous position information to form the tracking error for the PD control. Our results show that the motion control of swimming and station holding has been achieved by this simple but effective feedback control without large overshoot when approaching the target at different flow conditions and actuation force formulas. Although the swimming distance remains the same, a plate whose initial position is closer to the cylinder requires less energy expenditure to swim to the target location and hold the station there. This is because the low-pressure zone near the trailing edge of the plate is reduced in size, which provides drag reduction, contributing to reduced swimming energy. A higher Reynolds number also leads to energy savings. Under the same control strategy, the swimming performance is more affected by the force-frequency while the phase shift of the actuation force has a less significant impact.
Highlights
Aquatic animals provide ample prototypes for the design of efficient artificial underwater robots and vehicles
Considering that a fish tends to hold station in front of the cylinder in a uniform flow, as reported in an experimental study by Liao et al (2003), we focus on the swimming of a flexible plate whose actuation force amplitude is dynamically adjusted in front of a cylinder via a feedback controller, as shown in figure 1
The swimming and station-holding performance of a flexible plate in front of a fixed cylinder in a uniform flow is numerically studied by using a high-fidelity fluid–structure interaction (FSI) solver
Summary
Aquatic animals provide ample prototypes for the design of efficient artificial underwater robots and vehicles. Published papers reported pioneering applications of large eddy simulations to study more fish-like selfpropelled virtual swimmers in turbulent flow conditions (Bottom Ii et al 2016, Daghooghi and Borazjani 2015, Ogunka et al 2020). These studies improve our understanding of fundamental hydrodynamics during the locomotion of swimming fish. Biological observations by Shuler et al (1994) revealed that brown trouts in rivers prefer a feeding site that is near wing dams, midchannel boulder clusters, and natural bank cover, but avoid areas without structures Another example is that dolphins are seen to ride the bow wake wave behind ships (Scholander 1959)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.