Fluid modelling of atmospheric dispersion in the convective boundary layer

Abstract

A laboratory convection tank has been established following the pioneering work of Willis and Deardorff, but with many improvements and enhancements that take advantage of modern technology. The main emphasis in the current design was to provide the ability to conduct a virtually unlimited number of realizations under essentially identical conditions in order to obtain reliable statistics on the dispersion of plumes and puffs released within the simulated atmospheric convective boundary layer. Described herein is the tank itself and its auxiliary systems, including a laser-induced-flourescence and video-imaging system for making non-intrusive, full-field measurements of concentrations, and the interfacing of various subsystems with a master controller that automates essentially all operation and measurement functions. The current system provides unprecedented resolution, control, and data volumes. Example results are presented from two types of releases: continuous plumes and instantaneous puffs. These data sets clearly show penetration of the highly buoyant plumes and puffs into the inversion above the convective boundary layer, gravity spreading within the inversion, and rapid diffusion within the mixed layer. They also show extreme 'spottiness' in the instantaneous concentration cross-sections.