This project analyzes the effectiveness of common modeling approaches for predicting the wave load on two multi-member offshore wind turbine substructures, a tripod and a jacket. The tripod analyzed is from the International Energy Agency (IEA) Wind Task 23 Subtask 2 Offshore Code Comparison Collaboration (OC3) project and the jacket is from the Task 30 Offshore Code Comparison Collaboration Continuation (OC4) project. Traditional methods for calculating wave loads are based on Morisons equation, and its accuracy needs to be critically examined for complex structures involving multiple jointed connections and tapered and tilted members. This analysis is based on computational fluid dynamics (CFD) models, and is performed in the commercial code STAR-CCM+. The presented models solve the Reynolds-averaged Navier-Stokes equations. The free-surface flow is resolved by means of the interface-capturing Volume-of-Fluid method. Three different wave fields are modeled: linear regular, non-linear regular, and linear irregular. A still water case is also modeled as a reference. Results will be used to verify Morison forces and buoyancy loads calculated by HydroDyn, the hydrodynamics module within the wind turbine design tool, FAST.
The figure below illustrates the perscribed STAR-CCM+ model grid around the base of the a wind turbine. Notice the compact grid around the structure to better understand the forces.