SIMULATION OF DIFFUSION PHENOMENA UNDER UNSTABLE CONDITIONS USING A LAGRANGIAN PARTICLE DISPERSION MODEL

The Lagrangian particle dispersion model is one of the best techniques among numerical models of atmospheric diffusion, which is applicable to complicated flow fields generated by topography and heat. The autho rs have conducted wind tunnel experiments for unstable conditions, and examined how to consider the spatial variation of turbulent statistic s and non-Gaussian turbulence for the simulation of these experimental results with a Lagrangian particle dispersion model. In the case of c omputations under conditions where the changes in turbulent statistics in the downwind direction are taken into consideration, the results o f computation are in good agreement with those of the wind tunnel expe riment. Results of diffusion calculation were insignificantly influenc ed by skewness of velocity fluctuations.