DEVELOPMENT OF A PLUME RISE MODEL

Abstract

Plume Rise prediction forms the integral part of any dispersion model. There are many empirical and theoretical models to predict plume rise but each comes with their inherent limitations. The theoretical models are better, efficient as they can be used in a variety of conditions as the basics of plume rise phenomenon are taken into account. All models assume the cross section of plume as a perfect circle which has been proved wrong by recent studies done on cross sections of isoconcentration of species.(Parskovsky et al,1996) In this dissertation a model has been proposed to predict plume rise by taking into account the recent know-how about the actual plume cross section and the atmospheric turbulence induced entrainment and extrainment phenomena. The entrainment has been assumed occurring due to the relative motion of plume with respect to atmosphere and the basic differential equations have been derived which govern the plume dynamics. The equations thus derived have been solved using LABFIT® software for available set of field observations and the solution (rise) have been compared with their real field values. The model has been compared with the 2 most widely used models viz. Briggs model (Briggs,1969) and Moores model (Pasquill and Smith, 1983)) and the results show that the proposed model works well under various stability condition and shows a correlation value of about 0.99 with real values of rise. Other statistical parameters like normalised mean square error (NMSE), Fractional bias and Factor of Two (FAC2) are also well within the permissible limits. Keywords: Plume rise; entrainment