A General Lagrangian Approach to Simulate Pollutant Dispersion in Atmosphere for Low-wind Condition

Abstract

In this work we present a semi-analytical Lagrangian particle model to simu late the pollutant dispersion during low wind speed conditions. The model is based on a methodology, which solves the Langevin equation through the assumption that coefficient of the integrating factor is a complex function. The method leads to a non-linear stochastic integral equation, which is solved by the Method of Successive Approximations or Picard's Iterat ive Method. Taking into account the isomorphis m between the co mp lex and real p lane by writing down the low wind fo rmulat ion in polar form, the procedure allow to determine a formu la for the lo w wind direction. Furthermo re, an exp ression analogous to the Eulerian autocorrelation function suggested by Frenkiel(1) appears in the real co mponent solution. The model results present an improvement in relat ion to the other models and are shown to agree very well with the field tracer data collected during stable conditions at Idaho National Engineering Laboratory (INEL).