Numerical Simulation of Atmospheric Flow and Stack Gas Diffusion under Building and Complex Terrain Conditions : Estimations of Effective Stack Height and Comparisons with Wind Tunnel Experiments(<Special Issue>Urban Air and Environment Control Technologies)

A numerical simulation method has been developed to predict atmospheric flow and stack gas diffusion under a neutral stratification condition, considering the buildings and complex terrain located near and relatively far from a stack, respectively. The turbulence closure technique was used for flow calculation, some calculation grids on the ground within a plant area were treated as buildings, and stack gas diffusion was predicted using the Lagrangian particle model. The calculated flow and stack gas diffusion results were compared with those obtained by wind tunnel experiments under a neutral stratification condition, and the features of surface concentration, such as the occurrence of downdraft phenomena behind the buildings, were reproduced by both calculations and wind tunnel experiments. Furthermore, effective stack heights were estimated by the comparison of the surface concentration along the plume axis with those under a flat-plate condition, and it was apparent that the effective stack heights estimated by calculations were almost the same as those obtained by wind tunnel experiments.