Numerical study of compact debris in tornadoes at different stages using large eddy simulations

Abstract

Debris in tornado is one of the factors causing damages. However, it is difficult to model the debris in physical experiments using the available scaled tornado simulators. Numerical simulations provide an alternative way to investigate the tornado-induced debris. Therefore, in this study, the tornado-induced debris was numerically modeled using large-eddy simulations (LES). The most important parameter governing the tornado structures was the swirl ratio, which was varied to be 0.4, 0.6, 1.0, and 3.8. Compact debris was considered and the Tachikawa number was varied to be 12.8 and 32.1, corresponding to wooden sphere with diameters of 5 ​cm and 2 ​cm, respectively. The debris distributions and velocities were examined. It was found that, in the tornado core region, there is almost no debris for the all types of tornadoes. In addition, only when the debris diameter is 2 ​cm and the tornado is at the multi-celled stage, the debris velocities can show similar distributions with the corresponding wind field. Further, the probability density function (PDF) of the debris velocity shows strong non-Gaussian characteristics for the tornadoes with swirl ratios of 0.4, 0.6, and 1.0.