An evaluation of topographical effects on neutral and heavy-gas dispersion with a CFD model

摘要

Three different scenarios are studied to estimate how different structures at the side of a road, influence concentration levels. A solid fence gives the strongest effect on concentration. It forces the mean flow to move vertically which promotes mixing in the wake behind the fence. A hedge reduces the level of turbulence and the level of concentration becomes higher due to less turbulent dispersion. A road-valley generates turbulence in an intermediate regime. It captures a part of the plume in the valley which gives high concentrations locally. Atmospheric stability increases the concentration levels at a distance from the topographical disturbance. A heavy gasplume encountering a solid fence is broadened in front of the fence depending on the height of the fence and internal stability in the plume. The relation between these parameters, wind speed and the source rate will also affect the level of concentration downwind the fence.