Tornado missile transport analysis

Abstract

A methodology has been developed to simulate the initial release conditions and subsequent motion of objects transported by tornadoes. A probabilistic three-degree-of-freedom trajectory model which includes drag, lift, and side forces has been developed to simulate rigid body dynamics in turbulent tornado flow fields. Comparisons of this random orientation model to results from ballistic three-degree-of-freedom trajectory analysis are presented and the results suggest that the simpler models are potentially unconservative in predicting missile range and impact velocity. A missile injection methodology has also been developed which treats injection as the composite of all missile interactions in the near-ground domain and relies on a restraint force exceedance criterion to initialize missile release relative to the translating tornado. The aerodynamic forces acting on a potential missile during injection suggest a multi-peaked time history which is significantly influenced by missile offset position from the vortex center. A simulation study of missile injection has been performed to determine a conservative range for the assumed horizontal restraining force.