Hybrid DMST model for high-solidity straight-bladed VAWTs

Straight-bladed vertical-axis wind turbines (SBVAWTs) have unsatisfactory power generation and self-start ability due to continuous variation of attack angle to the blades. This study attempts to propose a proper analytical tool for high-solidity SBVAWTs since high-solidity SBVAWTs could be valuable in application for their comparatively low operational speed and good self-start performance. The applicability of the double-disk multiple stream-tube (DMST) model, which is a mainstream tool for SBVAWTs, is first examined for high-solidity SBVAWTs using the measurement data of aerodynamic forces on the blades obtained from wind tunnel tests. It is found that the complex flow field around the high-solidity SBVAWT introduces difficulties for the current DMST model to make satisfactory predictions. A hybrid DMST model, which uses the attack angle-dynamic aerodynamic force coefficient relationship established based on the measurement data, is then proposed. The aerodynamic forces estimated from the proposed hybrid DMST model manifest that the hybrid DMST model could predict the aerodynamic forces on the blades of the high-solidity SBVAWT with higher accuracy than the existing DMST models.