Numerical Simulation Of Tornado Wind Field And The Impact Of Wind Load On Wind Turbine Blades

Tornado is a violently rotating regional small-scale atmospheric vortex, which isgenerated suddenly, and grows and decays quite soon. The wind speed usually reachesfrom tens of meters to one hundred meters per second or more, which has extremelystrong destructive effect. Once important buildings such as wind farm are struck bytornado, and will cause serious personal and property losses. Therefore, the research onthe tornado wind field characteristics will be crucial to provide guidance and basis forfurther study about tornado load on building structures.In this thesis, three-dimensional flow characteristics of tornado vortex for a set ofswirl ratios (S=0.2,0.42,0.64,1.0and2.0), which is produced by an improvedWard-type tornado simulator, are numerically studied by Fluent software. Compare withtangential velocity of tornado vortex, the radial and vertical velocity are very small. Sothe tornado wind field characteristics are investigated for different swirl ratios basedprimarily on tangential velocity and static pressure distribution. Then the distributioncurves of simulation results are compared with the curves of traditional Rankinetheoretical model to prove the rationality and accuracy of numerical simulation.Moreover, the additional translational motion and surface roughness are introduced towind field above, and the impacts on the tornado wind field are analysed deeply. Theresults show that, compared with stationary tornado vortex, for lower swirl ratios, thetranslation reduces tangential wind speed and static pressure deficit, but the drop rangesof above parameters tend to decrease with the increase of swirl ratio. The introduction ofsurface roughness brings about a diminution of the maximum tangential velocity aroundthe ground, and the roughness causes an effect similar to reducing the swirl ratio.In addition, wind turbine of stop running and feathering is loaded in the tornado,and the distribution characteristics of its surface wind pressure are explored. Furthermore,the effects of different wind turbine locations on surface pressure in the tornado windfield are also examined. The results presented from this invesitgation will providetheoretical basis for anti-tornado design of wind farm.