Study On The Characteristics Of Wind Farm Around Wind Turbine Tower

Wake effect leads to wind speed reduction and turbulence intensity increasement in the wake region of wind turbines.The former can lower power generation efficiency and the latter can affect aerodynamic characteristics and fatigue loading,that will decrease the service life of wind turbines.It has considerably negative influence on the performance of downstream wind turbines and becomes an essential issue in the wind farm wake research.Therefore,threedimensional CFD(Computational Fluid Dynamics)method is adopted to simulate single 2-bladed wind turbine and two 2-bladed wind turbines at rated operating conditions.The flow field parameters were simulated by solving incompressible Reynolds Averaged Navier-Stokes(RANS)equations and incompressible Renormalization Group(RNG)k-? equations,which employs a cell-centered finite volume method.The flow field distribution of wind wheel wake flow is studied by numerical simulation.The flow fields were investigated,The results show that :When the separation distance of wind turbines perpendicular to the prevailing wind is 4D(D is the diameter of the wind turbine),although it has little effect on the power generation efficiency and velocity distribution in the horizontal direction,the difference in the velocity distribution in the vertical direction is significant.For the wake flow of single wind turbine,both horizontal velocity distribution and vertical velocity distribution are almost symmetrical with respect to the axis of rotation.But for two parallel wind turbines downstream,the horizontal velocity shows symmetrical characteristics only due to the mutual interference effects,with the velocity distribution curves offseting toward +Z coordinate axis.When the prevailing distance in the wake ranges from four times to eight times of the rotor diameter,mutual interference effects is serious.The velocity deficit in the wake flow is reduced gradually.For the coaxial arrangement of single wind turbine,the separation distance in prevailing wind direction should be ten times of the rotor diameter.But the separation distance along the mean wind should be eleven times of the rotor diameter in the wake region of two parallel wind turbines.The tower shadow causes the downstream velocity deficit,which has some influences on the power generation of wind turbines in the wake region,so it is necessary to be considered for the determination of the arrangement form of the wind turbines.