A low order model for vertical axis wind turbines

Abstract

A new computational model for initial sizing and performance prediction of vertical axis wind turbines is presented. The model uses a 2D hybrid dynamic vortex and blade element momentum approach. Each airfoil is modeled as a single vortex of time varying strength with an analytical model for the influence of the shed vorticity. The vortex strengths are calculated by imposing a flow tangency condition at the three-quarter chord location on each airfoil, modified in the case of stall. The total blade forces and the momentum-based streamtube deceleration are then obtained using pre-computed c[subscript d] and c[subscript m] 2D blade profile characteristics. Model fidelity is improved over previous models because flow curvature, dynamic vortices, blade interactions, static stall, and streamtube changes are all taken into account. Fast convergence is obtained for a large range of solidity and tip speed ratio, which allows optimization of various parameters, including blade pitch angle variation.