Blade-Resolved Numerical Simulations of the NREL Offshore 5 MW Baseline Wind Turbine in Full Scale: A Study of Proper Solver Configuration and Discretization Strategies

Abstract

This paper presents a blade-resolved numerical investigation of the NREL 5 MW baseline wind turbine for offshore applications including blade-tower interference, analyzing the solver configuration and its influence on the results accuracy and computational costs. The wind turbine was analyzed considering its full dimensions under the operating condition of optimal wind-power conversion efficiency for a wind speed of 10 m/s at hub height. The power production, generated thrust, and forces distribution along the blade span were estimated from the URANS simulations employing the k-ω SST turbulence model. We considered different approaches of the Pressure Implicit Split Operator (PISO) solver and different mesh refinement strategies for the spatial discretization process, which resulted in two different meshes being investigated. For one of the meshes, a temporal discretization analysis was performed for three different CFL numbers. The iterative form of the PISO algorithm was considered in its generic form and with an extra step to correct the pressure before the beginning of the iterative process in each time step. We also measured and compared the computational cost of each approach. Finally, detailed information regarding the flow characteristics is presented.

Keywords: NREL 5 MW Wind Turbine, Blade-resolved Simulations, Iterative PISO Solver, Spatial and Temporal investigations, Computational Cost Analysis.