Numerical study of debris flight in tornado-like vortices

Huo, Shen Shuan Ryan (2021). Numerical study of debris flight in tornado-like vortices. University of Birmingham. Ph.D.

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Abstract

The dangers and damages caused by tornadoes and the associated flying debris have been an issue and long been recognised. Whilst the flow fields of tornadoes and debris flight under different wind conditions have been investigated comprehensively, the study on tornado-induced wind-borne debris were surprisingly sparse.

The aim of this research is to characterise tornado flows and evaluate the flying behaviour of debris in tornado flows. Two tornado-like vortices with different swirl ratios were numerically generated using Large-eddy simulation and the trajectories of five groups of compact debris with varying Tachikawa number were computed using Lagrangian particle tracking. An analysis of the simulated flow field revealed that the two tornado-like vortices have different characteristics but similar flow structure; a core with downwards flow and vortex walls with high tangential velocity and updraft flows around the core. The investigation on debris fight behaviour showed that in both of the vortices, low mass debris group with high values of Tachikawa number had the highest tendency to become wind-borne and had the longest flight duration with considerable variability observed in debris trajectories. However, the high mass debris group with low values of Tachikawa number were observed to have greater impact range despite the short flight duration; this was due to the high mass debris being ejected out of the vortex with greater inertia, while debris with a lower mass had a tendency to circulate around the vortex. Finally, the initiation and flight altitudes of all wind-borne debris were found to be directly correlated with the updraft flows of the vortices.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):