A three-dimensional six-degree-of-freedom windborne debris trajectory model for tornadoes

Abstract

Windborne debris is a major cause of damage to the built environment during tornadoes. A fundamental step for quantifying this damage is to provide models that are able to describe the trajectory of the flying debris and thereby determine their impact location and associated momentum/energy. This goal can be achieved through the adoption of an appropriate three-dimensional (3D) six-degrees-of-freedom (6DOF) debris trajectory model. However, existing 3D 6DOF debris trajectory models are focused on describing the debris flight in straight line winds and therefore cannot be applied to tornado winds that are characterized by relatively small but rapidly rotating vortices. This paper presents a 3D 6DOF debris trajectory model for describing the flight of windborne debris in tornadoes. The proposed solution strategy is based on a predictor-corrector time-marching scheme which solves the equations of motion for each time step while updating the wind field from an appropriate tornado wind field model. A convergence analysis is carried out to determine the suitable time step that balances the accuracy of the numerical scheme with the computational run-time. The proposed model is then used to show the significant difference in modeling the debris trajectories in tornado wind fields as compared to straight line winds. • A six-degree-of-freedom windborne debris trajectory model for tornadoes is presented. • The proposed solution strategy is based on a predictor-corrector method. • The time step is determined by balancing accuracy and efficiency. • Limits of straight-line winds in modeling the flight of debris in tornadoes is shown.