Users' guide for numerical modeling of buoyant plumes in a turbulent, stratified atmosphere

Abstract

A widely applicable computational model of buoyant, bent- over plumes in realistic atmospheres is constructed. To do this, the two-dimensional, time-dependent fluid mechanics equations are numerically integrated, while a number of important physical ap- proximations serve to keep the approach at a tractable level. A three-dimensional picture of a steady state plume is constructed from a sequence of time-dependent, two-dimensional plume cross sections--each cross section of the sequence is spaced progres- sively further downwind as it is advected for a progressively longer time by the prevailing wind. The dynamics of the plume simulations are quite general. The buoyancy sources in the plume include the sensible heat in the plume, the latent heat absorbed or released in plume moisture processes, and the heating of the plume by a radioactive pollutant in the plume. The atmospheric state in the simulations is also quite general. Atmospheric var- iables are allowed to be functions of height, and the ambient atmospheric turbulence (also a function of height) is included in the simulations.