Plume rise: a revisit of old problems and some new ones

Most industrial pollution sources are stacks with discharges of momentum

and heat, and the resulting plume rise can be considerable (100's of

meters) and can lead to substantial dilution of plume constituents before

they reach the ground. For power plants and other large sources, the

major contribution to the rise is from the heat or buoyancy flux whereas

source momentum can be important for smaller sources typically found

in light manufacturing. Plume rise varies not only with the source

conditions but also with the local meteorological conditions---the wind

speed, ambient stratification, and the ambient turbulence---and is a

strong function of the downstream distance. In this paper, we focus

on an integral model of plume rise (Briggs, 1994; Weil, 1988) in which

one considers the differential equations governing the total fluxes

of mass, momentum, and energy through a cross section. The equations

are closed using an entrainment assumption. This approach has been

successful in predicting the rise and growth of plumes close to the

source and the "leveled off" height in stable air.

Key attention will be given to two unresolved historical plume rise

issues: 1) the penetration of an elevated inversion by a buoyant plume,

and 2) the prediction of the "final rise" due to turbulence in a

neutral or convective boundary layer. A more recent problem is the

rise, growth, and behavior of a buoyant plume in or near the

aerodynamic turbulent wake of a building. These problems are analyzed

using the governing theory or model together with laboratory

experimental data and field observations.