Plume Gaussian profiles

The measurements of Rouse, Yih and Humphries (1952) [1] helped to generalize the temperature and velocity relationships for turbulent plumes from small sources, and established the Gaussian profile approximation as adequate descriptions for normalized vertical velocity (w) and temperature (7), e.g. 

Properties are assumed uniform across the plume at any elevation, z. This is called a top-hat profile as compared to the more empirically correct Gaussian profile given in Equation (10.1). 

Table 10.2 gives correlation results based on Gaussian profiles with [3 selected as 1 for the axisymmetric and line-fire plumes [12]. It is indeed remarkable that the local ... 

A good example of dispersion is a plume of smoke being swept away by the wind. This plume will normally assume a Gaussian profile, a bell-shaped curve whose width is a function of the dispersion coefficient. If the amount of smoke emitted per time S is a constant, then the concentration of material in the smoke is given by (Seinfeld, 1985)... 

The Gaussian plume illustrated in Figure 6 represents the cross-section of a time-averaged, tracer concentration. That is, if time-series concentration measurements taken at a number of points across the plume were separately averaged over their duration, then one would expect to obtain a Gaussian profile. However, at any one time the instantaneous concentration profile would look very different. Figure 12, a typical instantaneous concentration cross-section, shows the small-scale concentration fluctuations resulting from the interaction of coherent structures... 

This model does a good job of predicting the general shape of the smoke plume. It predicts that the maximum smoke concentration Sj4nDappx) does drop as x increases. It does predict that the smoke spreads out in a roughly Gaussian profile, just as is observed. Thus diffusion theory apparently can be applied successfully to the release of pollutants. 

The earliest and still widely used dispersion model to compute pollutant concentration profiles is the Gaussian plume model for single or multiple source pollution problems. Box-type model techniques, which can take into account nonlinear interactions among different species arising from chemical reactions, have been used in longer-range dispersion computations. 

To model the transition of the plume between the neighbourhood and mesoscale regions, it is usual (as with other Gaussian plume models, e.g. Pasquill and Smith, 1983 [484] Hunt et al., 1988 [286, 287]) to estimate approximately the plume profile by one (or more) reflection terms when [Pg.78]

The passive gas dispersion models are usually based on the Gaussian plume model. In Gaussian models, atmospheric dispersion is taken into account through empirical dispersion coefficients that vary by atmospheric turbulence class (stability class) and distance from source. Dilution by the wind is taken into account through division by wind speed. No consideration, however, is given to the difference of the density between the ambient air and the gas, other than to calculate an initial plume rise if the release is hot (buoyant plumes rise according to relatively well-established approximations and then behave as a plume characterized by Gaussian concentration profiles). Because of this, these models must only be used for gas mixtures with a density approximately the same as that of air. 

Purpose. Neutral and positively buoyant plume or puff models are used to predict average concentration and time profiles of flammable or toxic materials downwind of a source based on the concept of Gaussian dispersion. Plumes refer to continuous emissions, and puffs to emissions that are short in duration compared with the travel time (time for cloud to reach location of interest) or sampling (or averaging) time (normally 10 min). 

---