Study On Three-dimensional Flow Field And Steady-state Characteristics Of Wind Turbine Tower

The rapid development of high technology has promoted a huge leap forward in human society.The demand for energy has also been increasing in the process of continuous progress in human society.Meanwhile the problem of energy shortage has also become increasingly prominent in various countries.Wind power stations are energetically developed all over the world for its clean and low cost.The wind turbine tower is very important for safe operation of the wind power station since it is a high-rise structure as the main component of the wind power generator.Analyzing the static characteristics and the dynamic characteristics of the wind turbine tower is important for the safety of wind power generator.At present,the influence of the environmental wind field on the wind turbine towers has not been fully considered in references.Because the wind turbine tower is tall,the external wind field has great influence on the response of wind turbine tower in the plain area.For some special conditions,wind turbine towers will be set on slopes with complex terrain.Studying the characteristics of the wind field in the selected area will help to provide solutions of the wind resistance design and wind-induced vibration for wind turbine tower.In view of this,the topography environment and the meteorological wind environment in the site of the wind turbine tower are considered in this paper.Then,the steady state effect of the wind tower under the external wind field is calculated.It is helpful to obtain the characteristics of the velocity flow field and pressure distribution around the wind tower,and the variation of the displacement and stress of wind turbine tower at different cases.The main research contents of the paper are included as follows.(1)The bending vibration equations of the wind turbine tower are deduced.The natural vibration characteristics of wind turbine tower are analytically analyzed.A finite element numerical model of the wind turbine tower is established.Natural frequencies are obtained by modal analysis.Natural vibration characteristics of the wind tower structure are analyzed.The results show that the low-order frequency is the main cause of resonance,and the effect of high-order frequency is less.(2)Flow field and wind tower model in three-dimensional is established based on COMSOL multi-physical field software for flat ground.Numerical simulations are carried to simulate the velocity and pressure distribution around the wind turbine tower.In addition,the displacement and stress distribution of the wind turbine tower are simulated.The three-dimensional wind flow field and the steady-state response of the wind tower under different incoming velocity boundary conditions are compared.The calculation results show that the maximum displacement of the tower is at the top of the tower,the displacement curve of the tower is almost like a parabola,and the displacement linearly increases with the wind speed.The maximum stress zone locates in the area of the windward and leeward side of the wind turbine tower near the ground.(3)A numerical model of the spatial interaction between the slope area and the wind tower is established based on COMSOL multi-physical field software.The characteristics of the wind field in the slope land are compared and analyzed,and different types of land surface roughness were analyzed for the wind field.The stress and displacement of the wind turbine tower at the slope land are compared with that at the flat ground.The variation of displacement and stress of the wind turbine tower in height are almost identical.But the variation of the stress of the wind turbine tower at the slope land has more fluctuation than at the flat ground.