Abstract
Wind velocity distribution and the vortex around the wind turbine present a significant challenge in the development of straight-bladed vertical axis wind turbines (VAWTs). This paper is intended to investigate influence of tip vortex on wind turbine wake by Computational Fluid Dynamics (CFD) simulations. In this study, the number of blades is two and the airfoil is a NACA0021 with chord length of c = 0.265 m. To capture the tip vortex characteristics, the velocity fields are investigated by the Q-criterion iso-surface (Q = 100) with shear-stress transport (SST) k-ω turbulence model at different tip speed ratios (TSRs). Then, mean velocity, velocity deficit and torque coefficient acting on the blade in the different spanwise positions are compared. The wind velocities obtained by CFD simulations are also compared with the experimental data from wind tunnel experiments. As a result, we can state that the wind velocity curves calculated by CFD simulations are consistent with Laser Doppler Velocity (LDV) measurements. The distribution of the vortex structure along the spanwise direction is more complex at a lower TSR and the tip vortex has a longer dissipation distance at a high TSR. In addition, the mean wind velocity shows a large value near the blade tip and a small value near the blade due to the vortex effect.
Highlights
Horizontal axis wind turbines (HAWTs) have developed rapidly since the aggravation of the fossil energy crisis
In order to investigate the effect of tip speed ratios (TSRs) on the aerodynamic characteristics of vertical axis wind turbines (VAWTs), Chen and Lian [14] studied the effects of solidity and TSR on the torque and power coefficients of wind turbines with Computational Fluid Dynamics (CFD) simulations on the basis of a Navier-Stokes solver
As mentioned in the Introduction section, the wind velocity, pressure distribution and torque can be measured by wind tunnel experiments
Summary
Horizontal axis wind turbines (HAWTs) have developed rapidly since the aggravation of the fossil energy crisis. With the increase of TSR, the low wind velocity regions had an expansion trend in the wind turbine wake They only studied the effect of TSR on the flow field of VAWTs, rather than the aerodynamic performance. In order to investigate the effect of TSR on the aerodynamic characteristics of VAWTs, Chen and Lian [14] studied the effects of solidity and TSR on the torque and power coefficients of wind turbines with CFD simulations on the basis of a Navier-Stokes solver. Parker et al [31] indicated the effect of blade tip vortex on the flow field and aerodynamic characteristics of VAWTs. Great advancements have been made in the studies on the flow field and vortex development for VAWTs. As previously mentioned, [15,29] Li et al measured the wind velocity around the wind turbine by using LDV system. The results obtained from the CFD simulations were compared to the measured data obtained from by the LDV technology from the wind tunnel experiments
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