Aerodynamic performance and characteristic of vortex structures for Darrieus wind turbine. I. Numerical method and aerodynamic performance

A recently developed in-house computational fluid dynamics (CFD) code is used to simulate an H-Darrieus wind turbine. Aerodynamic performance of the simulated Darrieus turbine having different number of blades and turbine solidity is analyzed and compared for different tip speed ratios. As expected, the power coefficient of the simulated Darrieus turbine increases with the increase of tip speed ratio until a maximum is reached. However, the power coefficient then decreases with further increases in the tip speed ratio. The calculated power curve is in good agreement with experimental results. The results obtained suggest that this developed CFD code can accurately predict the aerodynamic characteristics of an H-Darrieus turbine. In addition, it is found that the solidity has considerable influence on the power coefficient of the simulated turbine in the present work. The smaller the solidity, the higher will be the optimal tip speed ratio and the wider will be the range of tip speed ratios at which the H-Darrieus turbine remains high power coefficient. If solidity is very low, the performance of a 2-bladed Darrieus turbine is obviously better than that of turbines with 3 and 4 blades. For moderate to high solidity, the power coefficients of the 2-bladed Darrieus wind turbine are similar to those of the 3-bladed turbine and are higher than those of the 4-bladed turbine. Moreover, the power coefficient increases with increasing solidity at low tip speed ratios. When the tip speed ratio is close to the optimum value, the power coefficient initially increases and then decreases with the increase of solidity. At high tip speed ratio, the power coefficient decreases with increasing solidity. An in-depth investigation is also conducted on the findings observed in this study and presented in Part 2 of this work, in which the mechanism of the effect of solidity on power coefficient has been explored based on the vortex structure of the flow field with the aid of this self-developed CFD code.