Study of turbulence effects on flying compact debris in tornadoes at different stages

Abstract

Flying debris is an important factor influencing the destruction of buildings by tornadoes. However, research on tornado-borne debris remains limited. Thus far, the degree of this influence and methods to consider turbulence effects when predicting debris motion using the statistical information of wind velocities in tornadoes, have not been clarified. Therefore, in the present study, four methods for calculating debris motion based on the mean wind velocities and the root mean square of wind velocity fluctuations were examined. These four methods entailed (a) using only the mean wind velocities, (b) using Karimpour corrections, (c) assuming that the instantaneous flow fields of the tornado fluctuate as sinusoidal functions, and (d) assuming that the probability density functions of the instantaneous wind velocities follow Gaussian distributions. It was found that the debris concentration were sensitive to the turbulence in tornadoes. The Gaussian-distribution assumption afforded the best performances and could provide almost perfect predictions, except for the tornado-core regions.