Preliminary, one-way coupled, rain-droplets/airflow simulations over automobile

Abstract

In the present study, a simplified, one-way coupled, Discrete Droplet Method is proposed to model multiple rain-droplet motions over the vehicle wall. The Lagrangian method is employed to track the droplet, on which four forces are considered to act, i.e., aerodynamic drag, adhesion, viscous friction, and gravity. Based on the numerical experiment for one droplet, we assumed a "PATH" created by a droplet on the vehicle surface, meaning a wet region, on which the viscous friction was reduced once the droplet had passed. By taking this simple PATH effect into account, better agreements with the corresponding experiment were observed for multiple-droplet cases with different vehicle configurations and flow speeds. This method appears to have a good balance between accuracy and efficiency, and will potentially be applied to other engineering problems such as iced-aircraft.