Multi-Fidelity CFD Analysis of a Hydrokinetic Turbine in Uniform and Non-Uniform Inflow*

Hydrokinetic turbines operate in marine and riverine currents that can be non-uniform and have unsteady effects. Despite this, many studies assume uniform inflow conditions for the design of the turbine, which limits the understanding of the impact of non-uniform inflow on the force distribution along the blade span and the influence on the turbine performance. Accurately modeling the effects of non-uniform inflow on a hydrokinetic turbine is challenging but is also important to quantify the effects on turbine power performance, the wake effects, and the unsteady loading on the turbine blades.  The objective of this study is to investigate the influence of non-uniform inflow on the performance of a hydrokinetic turbine using Computational Fluid Dynamics (CFD) and to quantify the effects of different numerical approaches. The hydrokinetic turbine is modeled with a Reynolds-Averaged Navier-Stokes (RANS) Blade Element Momentum Theory (BEMT), which is computationally inexpensive since the effect of the turbine is modeled and not explicitly discretized. The discretized hydrokinetic turbine is also examined with both RANS and a hybrid RANS-LES (Large Eddy Simulation) approach. The results of each approach are compared to the experimental results from Bahaj et al., (2007) with uniform inflow conditions. Subsequently, the influence of non-uniform inflow conditions is assessed with the set of multi-fidelity approaches.