Thesis
A numerical study of fin and jet propulsions involving fluid-structure interactions
- Creator
- Rights statement
- Awarding institution
- University of Strathclyde
- Date of award
- 2021
- Thesis identifier
- T16182
- Person Identifier (Local)
- 201777987
- Qualification Level
- Qualification Name
- Department, School or Faculty
- Abstract
- Fish swimming is elegant and efficient, which inspires humans to learn from them to designhigh-performance artificial underwater vehicles. Research on aquatic locomotion has madeextensive progress towards a better understanding of how aquatic animals control theirflexible body and fin for propulsion. Although the structural flexibility and deformation ofthe body and fin are believed to be important features to achieve optimal swimmingperformance, studies on high-fidelity deformable body and fin with complex materialbehavior, such as non-uniform stiffness distributions, are rare.In this thesis, a fully coupled three-dimensional high-fidelity fluid-structure interaction (FSI)solver is developed to investigate the flow field evolution and propulsion performance ofcaudal fin and jet propulsion involving body and/or fin deformation. Within this FSI solver,the fluid is resolved by solving unsteady and viscous Navier-Stokes equations based on thefinite volume method with a multi-block grid system. The solid dynamics are solved by anonlinear finite element method. The coupling between the two solvers is achieved in apartitioned approach in which convergence check and sub-iteration are implemented toensure numerical stability and accuracy. Validations are conducted by comparing thesimulation results of classical benchmarks with previous data in the literature, and goodagreements between them are obtained.The developed FSI solver is then applied to study the bio-inspired fin and jet propulsioninvolving body deformation. Specifically, the effect of non-uniform stiffness distributions offish body and/or fin, key features of fish swimming which have been excluded in mostprevious studies, on the propulsive performance is first investigated. Simulation results of asunfish-like caudal fin model and a tuna-inspired swimmer model both show that largerthrust and propulsion efficiency can be achieved by a non-uniform stiffness distribution (e.g.,increased by 11.2% and 9.9%, respectively, for the sunfish-like model) compared with auniform stiffness profile. Despite the improved propulsive e performance, a bionic variablefish body stiffness does not yield fish-like midline kinematics observed in real fish,suggesting that fish movement involves significant active control that cannot be replicatedpurely by passive deformations.Subsequent studies focus on the jet propulsion inspired by squid locomotion using thedeveloped numerical solver. Simulation results of a two-dimensional inflation-deflation jetpropulsion system, whose inflation is actuated by an added external force that mimics themuscle constriction of the mantle and deflation is caused by the release of elastic energy ofthe structure, suggest larger mean thrust production and higher efficiency in high Reynoldsnumber scenarios compared with the cases in laminar flow. A unique symmetry-breakinginstability in turbulent flow is found to stem from irregular internal body vortices, whichcause symmetry breaking in the wake. Besides, a three-dimensional squid-like jet propulsionsystem in the presence of background flow is studied by prescribing the body deformationand jet velocity profiles. The effect of the background flow on the leading vortex ringformation and jet propulsion is investigated, and the thrust sources of the overall pulsed jetare revealed as well.Finally, FSI analysis on motion control of a self-propelled flexible swimmer in front of acylinder utilizing proportional-derivative (PD) control is conducted. The amplitude of theactuation force, which is applied to the swimmer to bend it to produce thrust, is dynamicallytuned by a feedback PD controller to instruct the swimmer to swim the desired distance froman initial position to a target location and then hold the station there. Despite the sameswimming distance, a swimmer whose departure location is closer to the cylinder requiresless energy consumption to reach the target and hold the position there.
- Advisor / supervisor
- Yuan, Zhiming
- Xiao, Qing
- Resource Type
- DOI
- Funder
Beziehungen
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PDF of thesis T16182 | 2022-03-24 | Öffentlich | Herunterladen |