The Influence of Uncertainty Factors in Modeling the Smoke Plume Rise in the Surface Atmospheric Layer

Ricardo Daniel Cardona de Sousa Bento

Key information

Authors:

Ricardo Daniel Cardona de Sousa Bento (Ricardo Daniel Cardona de Sousa Bento Bento)

Supervisors:

Francisco de Lemos Cabral Granadeiro Martins (Francisco de Lemos Cabral Granadeiro Martins); José Carlos Fernandes Pereira (José Carlos Fernandes Pereira)

Published in

07/17/2024

Abstract

This thesis aims to investigate the influence of the buoyancy flux, crossflow velocity, and source geometry on smoke plumes generated by wildfires. The plume buoyancy flux and jet to crossflow velocity ratio has an effect on the generation of the vertical coherent structures present underneath the plume, designated by wake and upright vortices. An increase of the buoyancy flux results in an increase of plume rise and plume expansion, as well as a decrease in the peaks of smoke concentration at a given distance from the source. A comparison is made with between the cross-wind integral of the smoke concentration and the Gaussian plume model, and the results were deemed satisfactory. The differences between low aspect-ratio rectangular source and linefire plume structures were outlined. The wavelength of the vortices generated by the latter was quantified and was shown to increase with the buoyancy flux. The generation mechanisms of the counter-rotating vortex pair were also shown to be different for the low and the high aspect ratio sources and non existent for infinite linefires. High aspect-ratio sources cause larger smoke concentrations at ground level due to poor lateral entrainment.