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.

风灾碎屑是龙卷风期间损坏建筑环境的主要原因。量化这种破坏的基本步骤是提供能够描述飞行碎片轨迹并由此确定其撞击位置和相关动量/能量的模型。通过采用适当的三维（3D）六自由度（6DOF）碎片轨迹模型可以实现此目标。但是，现有的3D 6DOF碎片轨迹模型集中于描述直线风中的碎片飞行，因此无法应用于以相对较小但旋涡迅速旋转为特征的龙卷风。本文提出了一个3D 6DOF碎片轨迹模型，用于描述龙卷风中的风载碎片的飞行。所提出的解决方案策略基于预测器-校正器时间步调方案，该方案求解每个时间步的运动方程，同时从适当的龙卷风风场模型更新风场。进行收敛分析以确定合适的时间步长，该时间步长使数值方案的准确性与计算运行时间保持平衡。然后，将所提出的模型用于显示与直线风相比，在模拟龙卷风风场中的碎片轨迹时存在显着差异。