Abstract
The purpose of this paper is to present the flow field with diffusion processes of air pollutant in a three dimensional numerical model. The previous model calculates a three dimensional wind field by using the mass consistent model that computes a total wind field from observed wind data on the ground at several observatory sites. Therefore, that model doesn't calculate the three dimensional momentum equations, and it approximates the wind velocities in each mesh point using the variational principle.Then, it causes the reduction of total computational CPU time in wind field computations. But, the previous model adopted the Cartesian Coordinates. so it has no good resolution of the topography for height data of the ground. In the present model of the Generalized Coordinates, the regular mesh system of the u, v and w flow field variables location is employed in order to cancel the truncation errors and to increase the resolution of the topography. This model strictly achieves numerical simulation of air flow, so we first determined the three-dimensional wind field of the entire Yokkaichi area from observatory wind velocity and direction data. Once the wind velocities in each computing mesh are obtained, next atmospheric diffusion and dispersion processes are computed by the convection diffusion equation. Using this method, we can trace the advection diffusion processes of diffused substances in the form of time development by the box model of finite-difference calculus. In this paper, the results of the real situation for sulphur dioxide diffusion processes from discharged smoke of petrochemical companies in Yokkaichi area in the past (in 1975) are shown. Computational results trend to agree well with real observed data in year averaged concentration analysis of sulphur dioxide.
