Study On Aerodynamic Interference Of Double Wind Turbines Under Typhoon Based On The Nesting Of WRF And CFD

With the large-scale development and effective utilization of global wind energy,the overall structure of wind turbine is also developing towards super flexible blades and super fine tower,which makes the wind damage problems of large-scale wind turbine system more prominent,erspecially in the southeast coastal areas of China where strong typhoons occur frequently.Compared with normal wind,the near surface wind field under typhoon is more complex.The wind field characteristics with high turbulence,variable direction and large shear wind speed will greatly increase the pulsation effect of wind turbine structures.At the same time,the turbulence of the air flow near the wall and the surface pressure change obviously,which makes the aerodynamic load and disturbance characteristics of the wind turbine system change significantly.However,most of the researches on typhoon resistance of wind turbines are based on theoretical analyses and measured data,so the theoretical system is simplified and it is difficult to reflect the specific wind profile and landing attenuation effect of mesoscale typhoon field.Moreover,it can not reflect the problem of aerodynamic disturbance of wind turbine in real typhoon field.In view of this,the weather forecast model(Weather Research and Forecast,abbreviated as WRF)based on non-hydrostatic equilibrium Euler equation model is introduced to simulate the typhoon ?Nuri? with high spatial and temporal resolution,and the boundary layer wind velocity profile is obtained based on nonlinear least square fitting after analyzing the characteristics of typhoon field.Then,two 5MW horizontal axis wind turbines in a wind farm in Shenzhen in the southeast coastal area of China are as the engineering background,and the wind loads and aerodynamic forces are studied systematically under different spacings,different wind direction angles,and different yawing angles based on small scale numerical simulation technology(Computational Fluid Dynamics,abbreviated as CFD).And the mechanism of pneumatic interference is revealed.There are four main aspects of the work:1.Determination of medium/small scale nesting scheme: the mesoscale WRF model and small scale CFD numerical simulation are introduced.Then,the nesting schemes in this paper are determined according to the characteristics of the two simulation methods,and the encryption scheme and nesting process are given.2.Simulation and analysis of mesoscale typhoon field: based on the mesoscale WRF model,the "Nuri" typhoon is finely simulated,and the selection of the simulation area,the selection of the physical scheme,the setting of the model parameters and the result information of wind field are introduced in detail.On this basis,the wind velocity profile near ground of typhoon is obtained,and the validity of typhoon simulation is verified by comparing the simulated path with the real path.3.Numerical simulation of small scale CFD and analysis of interference mechanism: combined with the small scale CFD numerical simulation method,the wind field simulation of two large wind turbines with different spacings,different wind direction angles,and different yawing angles is carried out.The formation mechanism of aerodynamic interference effect of the wind turbines under the different working conditions is analyzed from average wind pressure cloud,pulsating wind pressure cloud,velocity streamline and turbulent kinetic energy distribution.4.Study on aerodynamic force and interference effect of two wind turbines: the average wind pressure,fluctuating wind pressure,lift / drag coefficient values and distribution characteristics of two wind turbines under different working conditions are studied.Then,the spatial correlations of all measured points and the coherence characteristics of typical measuring points in the interference section are discussed.The interference factor is calculated based on the extreme value of the overall resistance coefficient of the tower,and the most unfavorable double-unit layout is analyzed and screened.In the end,the main research results are summarized in this paper.The main results are as follows: the typhoon "Nuri" in this paper is well simulated,and the typhoon profile index obtained by fitting is 0.118.The flow field characteristics,the pressure distribution,the correlation of fluctuating wind and the coherence of typical measuring points of front and rear wind turbines are different under different working conditions.The interference coefficient of front and rear wind turbines decreases gradually with the increase of distance between two wind turbines,increases first and then decreases with the increase of wind angle,decreases first and then increases with the increase of yaw angle.And the maximum interference factor can reach 1.335 under the most adverse working condition.The relevant conclusions can provide reference for the unit layout and typhoon resistance design of several wind turbines in wind farm.