Design And Flow Field Research Of Automatically Controlled Tornado Simulator

In the context of global climate change,tornadoes,as the product of extreme weather,are becoming more and more frequent,causing huge casualties and economic losses.Studying the laws of tornado formation,development,demise and flow field can effectively avoid the harm caused by tornadoes.At present,it is impossible to fully understand the characteristics of the flow field based on the measured data of tornadoes.However,using tornado simulator to generate tornado wind field in the laboratory and study its velocity distribution,vortex structure and other characteristics will help to deeply understand the characteristics and flow field structure of tornado and reduce the loss caused by tornado disaster.The current tornado simulators generally have disadvantages such as high cost and inconvenience for optical instrument measurement.It’s of great practical significance to develop a simulator with relatively low cost,good generation effect,and optical measurement requirements.Based on the extensive investigation of the existing simulators,this research designs a hexahedral cylinder structure tornado simulator,which is convenient for optical instrument measurement and has the advantages of automatic control and real-time multi parameter adjustment.The single-chip microcomputer embedded control design can better realize the real-time control of the updraft radius and the angle of the guide vane in the simulator.Through the high-speed camera and particle image velocimetry system,the reliability of the tornado flow field generated by the simulator is verified.Based on the tornado simulator designed in this study,the effects of radial Reynolds number and vortex ratio on the instantaneous vortex structure and time averaged flow field characteristics of tornado are discussed.The results show that:(1)Changing the radial Reynolds number has no significant effect on the tornado flow field.When the radial Reynolds number increases,the vortex morphology and the vortex core radius remain unchanged,the average maximum tangential velocity increases.As the radial Reynolds number increases,the normalized root mean square used to characterize the vortex wandering intensity remains almost constant,this means the radial Reynolds number has no effect on the vortex wandering intensity(2)The vortex ratio has a significant effect on the tornado flow field.The effect of vortex ratio on the flow field is similar by changing the radius of the updraft or the angle of guide vane.First,the structure of tornado can change from single vortex to double vortex to a certain extent.Secondly,in the single vortex state,with the increase of vortex ratio,the average vortex core radius increases,while the average maximum tangential velocity increases firstly and then decreases.Finally,with the increase of vortex ratio,the intensity of vortex wandering first gradually decreases and then becomes stable.In general,this study designed a tornado simulator with automatic control and real-time multi parameter adjustment.On this basis,it explored the main factors affecting the characteristics of tornado flow field,and expanded the relevant research on tornado flow field characteristics and structural changes.