Assessment Of Free Wake Aerodynamic Models On The Analysis Of Darrieus Vertical Axis Wind Turbines

Nowadays, wind energy has attracted a lot of attention in power generation for itsclean and renewable characteristics. Compared with the horizontal axis wind turbines,vertical axis wind turbines have some irreplaceable advantages, including: Simplestructure; Suitable for the low wind speed area; Flexible and convenient.However, the flow over the VAWT varies continuously during one revolution of windturbine, which makes the aerodynamic performance of VAWT even more complex thanHAWT. In this thesis, based on two Fortran codes, the aerodynamic model is estimatedand the aerodynamic performance of VAWT is investigated.(1) The method used in the code is introduced. The2D code is based on the ‘single wakemodel’, the3D code, which is named as GENUVP, is based on the ‘free-wake model’.The final codes are obtained by couple these two models with the dynamic stall modelrespectively to take the dynamics stall effect and viscous effect into consideration.(2) The codes are applied on the2D and3D wind turbine model. The comparison withexperimental result indicates that the predictions of the overall performance with2Dcode agrees well with the experiment. As for the instantaneous forces, the code canqualitatively predict the tendency of CN and CT. With the3-D code, the3D effect andthe influence of the taper at the tip of blade is investigated. The simulation indicatesthat at the tip of the blade, the power output is significantly reduced because of theinduced drag. The introduction of taper can effectively improve the power output andreduce the normal force. The comparison of prediction and experimental dataindicates that the results of the3D code agree well with the experiment at low andmedium tip speed ratio.(3) With the validated codes, the influence of solidity and swept angle on the performanceof VAWT is investigated.