Numerical simulation of rain scavenging on large release of water-soluble gases

A depth-integrated numerical model GPin was developed to calculate the behavior of neutrally buoyant, highly soluble gases subjected to scavenging by rain. A neutrally buoyant release of hydrogen fluoride is used to illustrate the use of the model. The GPin model was developed in two steps. The part without rain scavenging is based on AFTOX, a Gaussian puff/plume model. Then a first-order decay term for rain scavenging, which was developed by assuming a homogeneous rain field, was added to the concentration calculation for the puff. The model can predict the maximum release distance for a certain concentration limitation and a two-dimensional plume with or without rain.