Investigation Of The Aerodynamic Performance And Wake Characteristics Of Twin Vertical Axis Wind Turbines

With the large-scale exploitation of traditional fossil fuels,problems such as energy crisis have seriously affected the human society.Therefore,shifting towards clean and renewable energy such as wind energy is imperative.Wind turbines are commonly used to harness wind energy,given that vertical axis wind turbines(VAWTs)have the advantages of small size,low noise,suitable for working under turbulent flow,etc.The numerical simulation was used to study the aerodynamic performance and wake characteristics of VAWTs.An optimal computational fluid dynamics(CFD)mode of a standalone VAWT was selected via independence studies of parameters.At the same time,the results were compared with the previous experimental data,and a good agreement was found.Through the research on the aerodynamic performance of a standalone VAWT,it was found that with the increase of blade speed ratios(BSRs),the airflow flow phenomenon was significant.According to comparisons before and after the correction,the two-dimensional CFD simulations tended to overpredict the power coefficients at high BSRs.Through the analysis of the wake characteristics,it was observed that with the increase of BSRs,the wake velocity recovery became improved.In the cross-stream direction,the influence of wake flows was within one turbine diameter(1D).Taguchi robust design method was introduced to optimize the aerodynamic performance of the twin VAWTs arranged side by side.The orthogonal table of five parameters and four levels was designed for the optimization analysis.The order of influence of five parameters on the rated BSR was obtained: solidity > pitch angle > airfoil > rotational direction > turbine spacing.Correspondingly,the order of influence of five parameters on the power coefficient was determined: pitch angle > turbine spacing > solidity > airfoil > rotational direction.Through the orthogonal analysis,the parameters of the twin VAWTs under the optimal and worst configurations were determined.It was found that the power coefficients of the optimal and worst configurations of twin VAWTs were raised by 13% and 8%,respectively,from that of their standalone counterparts.With the optimal and worst configurations,the wake characteristics were analyzed.It was found that the twin VAWTs had small wake velocity deficits,and enhanced wake recovery.Based on the analysis results of the aerodynamic performance and wake characteristics,the twin VAWTs with the optimal configuration were taken as the basic unit.Different lateral and longitudinal spacings were used to perform full-factor optimization analysis of turbine layout design.The optimal lateral spacing was 3D,and the longitudinal spacing was 1.2D.It was also observed that the lateral spacing exerted a larger influence on the average power coefficient,whereas the longitudinal spacing had a greater influence on the power density.Through calculations,the average power coefficient with the optimal layout design was 20.3% larger than that of a standalone VAWT.