Characteristic Analysis Of Large Wind Turbine Wake Based On Fluid-structure Interaction

As the times progress and society advances, the demand for energy of thehuman is getting greater and greater. At present, with the normal energybecoming less and less and the pollution of the environment becoming moreand more serious, people are looking for new energy to add or replace thenormal energy for sustainable development. As one type of renewableelectricity-generation, the wind energy, which is inexhaustible and has a goodprospect of application, has now attracts more and more attentions of mostcountries in the world. In order to improve the utilization efficiency of windenergy more effectively, reduce infrastructure costs, large scale of the windfarm is the development trend. In wind farm,downstream of the wind turbinesof downstream are often in the wake of the wind turbine of the upstream, so theperformance of the wind turbine is affected．In order to design wind farmreasonably and improve the efficiency of wind farms, to carry out thecharacteristic analysis of large wind turbine wake based on fluid-structureinteraction is necessary．Because the wind turbine is running in complex environment conditions,The wind turbine will deformate under the action of wind, at the same time, thedeformation and movement will affect the movement of the wind in turn. Sothe two-way fluid-structure coupling analysis between wind turbine and windfield is indispensable. In addition, in order to study the complex operation onthe influence of the wind turbine in the actual work environment, the dynamicflow and the tower shadow effect should be considered．Thus based on thetheory of two-way fluid-structure interaction, this paper uses theANSYS+FLUENT and sliding grid technique to analyze the wakecharacteristics of NREL5MW wind turbine. To analyze the impact of dynamicflow to wake,this paper has chosen the representative normal vertical windshear, EWS, EOG and EDC four wind conditions．The program is compiledthrough the UDF and use it as inlet boundary conditions．Then ues the sliding grid technology to calculate． The results show that compared to no FSIcondition the output power of wind turbine and axial thrust are closer to theNREL design value in the wind turbine near wake zone,under fluid-solidcoupling．In the far wake area, the axial velocity eaqual to flow velocity earlierat X=6D,under two-way fluid-structure interaction.And turbulence intensitybegan to decline in advance at X=2D where is a inflection point,and at X=6Dreached9.8%, then into the low degree of turbulence flow field area．In thedynamic flow conditions,the power output of wind machine has volatility indifferent levels. The wake structure also appear obvious deformation fromblade root to tip. The existence of shadow effect makes the wind turbine torqueand power are reduced. Fierce mutation also appears on the lift of the towersurface. It will be harmful to the fatigue life of tower. Start from6Ddownstream of the wind turbine can ignore the tower shadow effect on thedistribution of the wind turbine wake effects. This article also puts forwardsuggestion which longitudinal spacing of downstream of the wind turbinenot isless than6times rotor diameter and transverse distance is not less than2timesthe rotor diameter in large wind farm. It will provide a certain reference basisfor optimum arrangement of the wind turbine in wind farm.