Numerical Simulation of Flight and Impact of Windborne Debris

Numerical methods to simulate flight and impact of windborne debris are described. The problems are treated as fluid–structure interaction problems based on the ALE finite element flow analysis in order to deal with arbitrary shape of flying objects as well as dynamical change of aerodynamic forces. For the flight simulation, the computational domain travels with the flying object because usually the fight distance is much longer than the size of the debris. For the numerical impact process, the magnitude of the impact force is determined by iteration so that the velocity of the sphere after impact converges to zero. Furthermore, in order to suppress unphysical step-by-step pressure oscillation, the time step at the impact is subdivided into a set of multiple short time steps with a smooth impact force function. Several numerical examples of a rigid sphere show satisfactory features of these methods.