Modeling and Analysis of Fluid-structure Interaction in Biomimetic Undulatory Swimming

Michigan State University, East Lansing MI

Investigators

Abstract

This grant will support fundamental research in aquatic propulsion mechanisms. This study will benefit science and engineering fields such as exploration, transportation, and defense, by boosting the development of bio-inspired locomotion based on the fundamental principles that make fish-swimming highly efficient and agile. Accurate modeling of the interplay between a flexible body and the surrounding fluid is crucial to understanding and optimizing energy consumption, speed, and maneuverability. Existing models of undulatory swimming are restrictive in the forms of motion and the flow conditions they can describe accurately. This study will help to overcome those restrictions by introducing more realistic body motion and flow conditions. A novel body-fin dynamical model will be developed that includes previously ignored key elements important for swimming performance. This research combines vibration theory, fluid and solid mechanics, and both numerical and experimental analyses, offering interdisciplinary research for graduate and undergraduate students, as well as creative activities for K-12 outreach including fish-design competitions. Undulatory swimming is a result of the nonlinear interaction between the body and surrounding fluid. Subtle changes in internal forcing and body deformation may induce significant differences in swimming performance. This award supports research that will address the fundamental challenges of accurate fluid-structure modeling under variable body-fin configurations with diverse swim gaits and conditions. A reduced-order model of undulatory swimming motion of a slender body as a forced hydroelastic oscillator will be developed to connect internal muscle forcing, external fluid forces, and body motion in an efficient approach based on state-variable modal analysis. Nonholonomic constraints on fins will be used to bypass the fluid-force prediction based on classical hydrodynamic models, which are restricted to idealized geometry and flow conditions. The use of nonsynchronous modes will enable the description of general body waves with longitudinally-varying properties. High-fidelity computational fluid-structure simulations, and innovative water-tunnel measurements based on refractive index matching, coupled with the structural analysis, will be used to investigate detailed features of the interactions between the fluid, structure, and neuromuscular activation and improve the reduced-order model. Then, the model will be used to evaluate optimized morphology and internal forcing patterns in viscous to inertial swim regimes, for uniform and complex background flows. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.