Development and validation of a tool for vertical axis tidal turbine performance evaluation in marine environments

The interest in hydrokinetic conversion systems has significantly grown over the last decade with a special focus on cross-flow systems, generally known as Vertical Axis Tidal Turbines (VATTs). However, analyzing regions of interest for tidal energy extraction and outlining optimal rotor geometry is currently very computationally expensive via conventional 3D Computational Fluid Dynamics (CFD) methods. In this work, a VATT load prediction code based upon the Blade Element-Momentum (BEM) theory is presented and validated against high-resolution 2D and 3D CFD simulations. The standard Double-Multiple Streamtube (DMST) model is enhanced through literature-derived and original submodels that account for phenomena such as dynamic stall, tip losses, streamlines curvature and streamtubes expansion. As a practical application, the code is employed for a site assessment analysis of the Cape Cod area to quickly highlight oceanic regions with high hydrokinetic potential, where further higher-order and more computationally expensive CFD analyses can be performed. Ocean data are obtained from data-assimilative ocean simulations predicted by the 4D regional ocean modeling system of the Multidisciplinary Simulation, Estimation, and Assimilation Systems (MSEAS) group of the Massachusetts Institute of Technology