Characteristics of compact debris induced by a tornado studied using large eddy simulations

Abstract

In addition to strong wind, tornado-borne flying debris is a major contributor to large destructions caused by tornadoes. However, research on flying debris is still very rare. In the present study, a specific tornado observed in nature is reproduced using large eddy simulations. The debris is assumed to consist of compact wooden objects with diameters of 2, 5, and 10 ​cm. The wooden objects are released at heights of 1, 5, 10 ​m, and 20 ​m. Instantaneous debris distributions, debris concentration, and statistics of debris velocities were systematically examined. The model shows that releasing debris at lower elevations or enlarging the size of the debris lead to greater debris dispersion and decrease the speed of debris. The fluctuations and maxima of debris velocities are globally less than those in wind. Among all of the cases studied, debris velocities can be estimated using wind velocities only when the debris diameter is 2 ​cm. The largest difference between the debris velocity and the wind velocity is found in tornado core regions. In the outer region, the velocity statistics for debris and wind almost converges except for the radial component.