Capture of wind-blown particles during transport through a vegetative barrier

Abstract

This study presents an efficient computational method for predicting the capture by vegetative barriers of wind-blown particles, such as sand, snowflakes, and exhaust from vehicular exhaust. The method assumes that the vegetative barrier is composed of a line of trees, where synthetic trees are formed using a network of cylindrical elements representing branches and needles, as is typical of pines and other evergreen vegetation. Computational fluid dynamics simulations are employed to determine the average wind velocity at the front of the vegetation and to calculate the particle flux entering the vegetative barrier. The vegetative barrier is treated as a heterogeneous filter medium, and an efficient method is used to compute the capture efficiency and penetration of particles into the vegetation. The particle capture computation method employs an estimate of the single fiber efficiency for each cylindrical branch/needle element based on models for finite Reynolds number particle capture from the literature. The method was employed for different vegetative barriers, which were characterized by varying porosities to assess their impact on particle capture efficiency. The proposed prediction approach is important for assessing effectiveness of vegetative barriers for protection of roadways from blowing snow and dust and for estimation of rate of vehicular pollution damage to roadside trees.