Abstract
This research investigates modeling the fluid-structure interactions (FSI) on the blades of a cross-flow turbine. In marine energy applications, the time-accurate simulation of fluid flows is challenging due to the geometric and kinematic complexity of the turbines. As the turbine blade rotates, it is exposed to a dynamic stall cycle of dramatic flow separation and reattachment which precipitates large changes in the blade-normal forces. These forces cause an intracycle heaving and pitching motion of the blade superimposed on its nominal circular motion.
The goal of this research is to accurately simulate the flow physics and performance effects of the FSI-induced non-circular path. Traditional dynamic meshing techniques such as sliding meshes often struggle to accurately emulate the complex kinematics of a turbine blade undergoing complex displacements. Overset meshes offer a robust solution to this issue. Using the overset meshing technique, structured or unstructured meshes containing bodies or regions can be overlapped with one another. This allows regions in the mesh to move independently without having to deform the surrounding mesh structures. While this simplifies the grid generation process and allows for complex and arbitrary kinematic profiles, the overset algorithm has a costly computational interpolation between each mesh layer. This research leverages the functionality of overset meshes to model the fluid-structure interactions of a cross-flow turbine, providing insights into the changes in performance and flow physics, and comparisons with alternative methods for pursuing non-circular kinematics of cross-flow turbine blades.
The results indicate only minor changes in time-averaged blade loading, however, the non-traditional path induced by the fluid-structure interactions does indicate shifts in the unsteady flow physics or dynamic stall process. This finding underscores the importance of accurately modeling FSI to fully understand the performance characteristics and flow physics of cross-flow turbines.