Flight characteristics of rod-shaped windborne debris objects in atmospheric boundary layer winds

Abstract

The presented study explored the flight characteristics of rod-shaped debris objects in neutrally-stratified atmospheric boundary layer (ABL) winds. Despite the fact that rod-shaped debris objects, such as lumbers, are a common type of debris observed during extreme wind events, their three-dimensional motions had not been fully characterized and the understanding of their flight trajectories was limited to the outcome of only a few wind tunnel tests. To address the outlined research gaps, this study established a coupled simulation framework, which utilized both computational fluid dynamics (CFD) and rigid body dynamics (RBD). After validating this framework using the experimental test data, the flight trajectories of a set of rod-shaped debris objects were first evaluated in uniform winds. With placing the rod's longitudinal axis in both along-wind and cross-wind directions, the debris flight motions were characterized for various initial pitch angles. After appropriate verifications, the simulations were extended to investigate the flight of rod-shaped objects in ABL winds. The main debris flight properties, including displacement and velocity profiles, were systematically extracted over time, taking into consideration various influential factors. With the wealth of debris flight data generated through the conducted CFD-RBD simulations, predictive models were developed for assessing the kinetic energy associated with the flight of rod-shaped debris objects.