Abstract
A three-dimensional computational fluid model is applied to the atmospheric diffusion evaluation of stack gas emitted from thermal power plants under complex terrain conditions for environmental assessment in Japan. Recently, the construction of many low stacks has been attempted instead of high stacks, due to the improvements in the thermal power plants facilities and the decrease in pollutant gas levels with the selection of high-quality fuels. In this study, a numerical simulation model of the diffusion of gas emitted from low stacks near the ground surface was developed using the nonhydrostatic formulation for flow, which takes into consideration the effects of terrain near the ground surface. Prior to the application of the developed numerical model to low stacks near the ground surface, the diffusion of gas emitted from high stacks, such as those of conventional thermal power stations, was simulated in this study. The surface concentrations of the stack gas were simulated and compared to those obtained in wind tunnel experiments. Furthermore, the ratios of the maximum concentration and its observed distance to those obtained under flat-plate conditions were also compared with other calculation results (Ichikawa and Sada, 2002) and wind tunnel experimental results. It was apparent that almost the same ratios could be obtained using the numerical simulation model developed in this study.
