Fluid-Structure Interaction Modeling of a Flexible-Inflatable Heaving Wave Energy Converter Through Generalized Modes

Abstract

The point absorber, one of the most popular types of ocean wave energy converter (WEC), usually consists of a rigid body buoy that can be efficiently modeled using existing WEC simulation tools. However, new wave energy technologies have looked to utilize flexible buoy structures to decrease costs, improve power generation, and increase portability. In addition to replacing rigid body designs, the combination of multiple renewable energy sources is another area that shows promising potential for increasing WEC power generation. With these concepts in mind, this work considers a new WEC design that features a flexible-inflatable buoy, an ocean current harvesting turbine, and a buoy shape that has been optimized for simultaneous wave and current energy harvesting. For this device, conventional modeling techniques cannot be used due to the highly nonlinear hydrodynamic interactions that result between the flexible buoy and the ocean waves. As a result, a Fluid-Structure Interaction (FSI) model must be used to determine how the flexibility of the buoy will influence the device's power generation. Currently, high-fidelity FSI modeling approaches are computationally expensive and unsuitable for early design decisions. As a result, this thesis utilizes a mid-fidelity method, the generalized modes modeling approach, to accurately and efficiently model the FSI of a WEC's flexible buoy. The resulting flexible buoy model was then compared to a rigid design to determine the performance differences between a rigid and flexible buoy, with a complex, optimized shape.