Automatic selection of release plane for Lagrangian-based wind-driven rain studies

Wind-driven rain (WDR) modelling based on Lagrangian particle tracking (LPT) involves the trajectory simulation of raindrops released from a horizontal plane in the computational domain. Usually, the release location is determined in a tedious trial-and-error manner, which impairs the adoption of LPT method for WDR studies in terms of user's handiness and computational efficiency. In this study, the analytical solution for raindrop trajectories in an unobstructed domain are derived and presented. Based on the analytical solution, the location and sizes of the release plane can be easily determined a priori. A constant scaling factor can be further introduced to address possible obstruction effects by buildings. Unnecessary and expensive repetition of simulations to search for a proper release plane can be avoided, especially for scenario studies involving multiple raindrop sizes. In this paper, the accuracy, efficiency and effectiveness of the proposed automatic selection of release plane based on the analytical solutions are demonstrated based on selected case studies. It is deemed that the proposed innovative procedure for the determination of an effective and appropriate release plane can promote the widespread adoption of LPT approach for WDR studies.

Automated summary

This study presents an analytical solution for raindrop trajectories in an unobstructed domain, which allows for easy determination of the location and sizes of the release plane. It eliminates the need for tedious trial-and-error methods and improves the efficiency and user-friendliness of raindrop trajectory simulations.