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

In this work we present a semi-analytical Lagrangian particle model to simulate 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 Iterative Method. Taking into account the isomorphism between the complex and real plane by writing down the low wind formulation in polar form, the procedure allow to determine a formula for the low wind direction. Furthermore, an expression analogous to the Eulerian autocorrelation function suggested by Frenkiel[1] appears in the real component solution. The model results present an improvement in relation 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).