A multi-fidelity CFD analysis of a tidal turbine in uniform and sheared inflows

Tidal turbine performance is strongly influenced by inflow velocity profiles, yet a multi-fidelity CFD comparison of performance, blade loading, and wake recovery in identical inflow conditions has not been fully addressed. In this study, four CFD methods of increasing fidelity are used to evaluate tidal turbine performance in uniform and linearly sheared inflow conditions. The methodology includes low-fidelity methods using Blade Element Momentum Theory (BEMT) coupled with CFD and high-fidelity blade-resolved simulations using Reynolds-Averaged Navier–Stokes and Improved Delayed Detached Eddy Simulations. All approaches show reasonable accuracy at peak performance. The sheared profile has a negligible effect on global performance but introduces unsteady loadings on the blades at different blade azimuthal positions. BEMT-based methods capture this trend well with significantly lower computational costs than the blade-resolved models. Loading variations in sheared inflow lead to asymmetric time-averaged wake distributions, captured in all models. Higher fidelity methods capture more unsteady features including the tip vortices, however the time-averaged flow fields are consistent between methods. BEMT-based methods are suitable for early-design-stage performance and time-averaged flow field predictions. For an in-depth analysis of the blade and inflow interaction and its effect on the instantaneous velocity field, blade-resolved simulations with higher fidelity turbulence models are required.