Study On Wind Turbine Wake Characteristics And Its Influence On Sand And Dust Transport In Wind And Sand Environment

Northwest China is not only a place with serious sandstorm and desertification,but also a place with abundant wind resources and dense wind farms.Sandstorms occur frequently in Northwest China.Wind turbines operate in the wind and sand environment for a long time.Sandstorm will affect the operation of wind turbines.At the same time,the operation of wind turbines will also affect the transportation of sand and dust.The hazards of sandstorm include but are not limited to farmland desertification,buried railway,grassland desertification and wind erosion of forest land.These phenomena are related to the deposition of sand particles.Therefore,the impact mechanism of wind turbine on sand and dust transportation is a problem very related to the environment.This study combines the methods of experiment and numerical simulation,and focuses on the wake characteristics of wind turbine in wind and sand environment and the influence of wind turbine on sand dust distribution and transportation.It mainly includes the following aspects:Firstly,based on OpenFOAM,a solver combining MP-PIC(multiphase partial in cell)method and actuation line method is proposed.The solver can realize high-precision calculation combined with large eddy simulation,and solve the problem that coupling simulation of wind sand and wind turbine consumes huge resources.Based on the solver,the wake and power characteristics of wind turbine in wind sand environment are numerically simulated.The results show that the wind turbine wake length is shorter and the wake is more easily disordered in the wind sand environment.The blade tip vortex and blade root vortex in the clean air environment are more stable,and the dissipation is less than that in the wind sand environment.Comparing the spectrum results of wind turbine wake velocity in wind sand environment and clean air environment,in the energy region and inertial sub-region,the turbulent energy in the wind sand environment is greater than that in the clean air environment.In the dissipation region,at most section positions behind the wind turbine,the turbulent energy in the wind sand environment is greater than that in the clean air environment,Comparing the output power of wind turbine and its spectrum in wind sand environment and clean air environment,it is found that the power output of the wind turbine in the wind sand environment is higher,but the power fluctuates greatly.Secondly,taking a wind turbine model designed by Gansu wind turbine engineering technology research center as the research object,the distribution characteristics of sand and dust particles under the wind turbine wake are explored.The results show that the distribution characteristics of sand and dust particles are related not only to the particle size,but also to the transportation distance:the Stokes number of 30 μm particle size sand and dust particles is less than 1,the diffusion is strong,and the spatial distribution is relatively uniform;The Stokes number of 70 μm sand dust particles is close to 1,which has selective aggregation and is concentrated at the leaf tip and root;The Stokes number of 100 μm sand dust particles is greater than 1,which has inertia,is greatly affected by gravity and is easy to settle.In the tip region,the dust particles have obvious aggregation characteristics,indicating that the tip vortex has obvious aggregation effect;In the blade root region,the number of dust particles is significantly less than that in the blade tip region,indicating that the aggregation ability of the blade root vortex is weaker than that of the blade tip vortex.Finally,the transport characteristics of sand and dust under the wake of wind turbine are studied from a macro point of view by using wind tunnel experiment.The results show that the wake vortex structure produced by the operation of wind turbine changes the spatial distribution of sediment transport flux.Without wind turbine,the distribution of sediment transport flux of different particle sizes presents Gaussian distribution.When wind turbine is running,the sediment transport flux forms a w distribution.After flowing through the wind turbine,the dust particles will be affected by the wake of the wind turbine.The dust transport intensity at the blade tip height increases and the dust transport intensity at the blade root height decreases.With the increase of transport distance,the dust transport intensity at the blade tip height and blade root height decreases.The transport capacity of the wind turbine wake to sand and dust particles with different particle sizes is different.At the height of the blade tip,the sand resistance of the wind turbine is the largest under the particle size of 100～200 μm,followed by 0～100 μm and the smallest under the particle size of 200～300 μm,indicating that the transport capacity of the blade tip vortex to 100～200 μm is the strongest.