Numerical simulations of combined effects of terrain orography and thermal stratification on pollutant distribution in a town valley

Abstract

Combined effects of terrain orography and thermal stratification on the dispersion of pollutants in a mountainous town valley over a diurnal cycle are numerically simulated by a time-dependent Reynolds-averaged Navier-Stokes (T-RANS) approach The T-RANS model was incorporated into a finite volume NS solver for three-dimensional non-orthogonal domains, using Cartesian vector and tensor components and collocated variable arrangement. Prior to the full scale simulations, the T-RANS approach was validated in test situations where the effects of thermal stratification and terrain orography are separated, showing good agreement with the available experimental and simulation data. The full scale simulations were performed in a realistic orography over two diurnal cycles for two cases of the initial thermal stratification, both with a prescribed time and space variation of ground temperature and pollutan temission - reflecting the daily activities in the town. The results confirmed that T-RANS approach can serve as a powerful tool for predicting local environments at micro and micro scales. © 2002 Springer-Verlag Berlin Heidelberg.