Numerical Study Of The Distribution Characteristics Of Tornado-borne Debris And Simplification Methods

With the deterioration of the global climate,tornadoes and other extreme natural disasters have attracted extensive attention.Tornado-induced building damages are mainly caused by its strong wind,large pressure gradient and the tornado-borne debris.With the development of observation equipments,wind tunnel experiment and numerical simulation technology,the characteristic of flow field in tornado has been studied systematically.However,due to the limitation of the observation and experiment,the third factor of tornado disaster,the damage caused by tornado-borne debris,is rarely studied.There is a consensus that turbulence will affect the motion of flying objects,but how it affects and how to consider it are still unclear.To analyze the distribution characteristics of tornado-borne debris,a method coupling the large eddy simulation(LES)and Lagrange particle tracking(LPT)is adopted.Based on this method,the effects of different debris size,release height and tornados swril ratio on the debris distribution characteristics are examined.Finally,for the sake of simplifying the simulation method,utilizing GPU acceleration,four methods are proposed to generate instantaneous wind field through the statistics of tornado flow field for debris simulation,and the accuracy of those methods are examined by comparing with the coupling method.It is found that debris is difficult to enter the tornado core region,and the tangential velocity of debris at the tornado core boundary is always greater than that in wind,which is one of the reasons for the difference between the tornado observation and the experiment.In addition,the instantaneous wind field generated by the method of Gaussian-distribution can provide almost perfect predictions for the characteristics of debris concentration and tangential velocity.