Results from a computational fluid dynamics (CFD) model of a vertical axis tidal current turbine are presented. This CFD model has been implemented in the commercial code CFX and is a Reynolds-averaged Navier-Stokes solution with the k-ω SST turbulence model. The turbine simulated is a 15 kW small-scale prototype device being developed by Edinburgh Designs Ltd. with independently and continuously variable pitch blades.
A major focus of the present work is the thorough verification and validation of the numerical model. This is based on a series of progressively more complex simulations, beginning with fixed pitch hydrofoils (airfoils), progressing to oscillating pitch hydrofoils, and finishing with a complete time-dependent model of the turbine.
The paper concludes with a parametric study of turbine performance, comparing fixed pitch and variable pitch operation and a four-bladed variant of the turbine with the three-bladed baseline. It is found that variable pitch operation both increases the peak power coefficient and broadens the peak in the power coefficient versus tip speed ratio curve. An increase in the number of blades (maintaining solidity) leads to a slight drop in performance, commensurate with Reynolds number effects.