MS Plan A Defense: Fluid-Structure Interaction Analysis of an Oscillating Wave Surge Energy Converter using LS-Dyna

Kyle Pappas
Master’s Student
Department of Ocean and Resources Engineering
University of Hawai’i at Mānoa

**This defense will be held both in person (POST 723) and over Zoom**
Meeting ID: 936 1681 5822
Passcode: KyleMS
https://hawaii.zoom.us/j/93616815822

Three-Dimensional two-way coupled fluid structure interaction (FSI) analysis requires a complex strategy utilizing the finite element method (FEM) for large matrix computations. Two FEM solvers in LS Dyna are utilized to conduct a structural analysis of the Hawai’i Wave Surge Energy Converter (HAWSEC) for a particular wave condition case study that is directly compared with experimental results. The HAWSEC is a hollow, surface piercing, bottom secured, flap type oscillating wave surge energy converter designed for nearshore applications. The Arbitrary Lagrangian Eulerian (ALE) solver produces high fidelity solutions utilizing an explicit solver to couple structural mechanics with the fluid domain. The Incompressible Computational Fluid Dynamics (ICFD) solver utilizes an implicit solver with larger timesteps, making use of a Newton loop to converge the structural part with the fluid part. While both solvers accurately produce the force and pitch angle of the flap, the ICFD solver stands out for its low computation time, and ease of modeling the FSI boundary. Leakage control issues in the ALE simulations are addressed to adequately contain most of the air inside of the flap. Applying a plastic kinematic material to the aluminum flap allows for stress and strain contours to be observed in either solver. While intuitive stress and strain contours are observed in the ICFD simulations, the ALE simulations present questionable results that may require further refinement in leakage control. It is therefore suggested to use the ICFD solver for this type of problem where the structure is hollow and very small time steps are not necessary. Utilizing accurate two-way coupled FSI simulations may streamline design processes for wave energy converter technology, reducing development costs, allowing for faster optimizations, and increasing reliability of the structure.