Plume physics

The integral plume theory is intended for application on lofted plumes. Physical aspects of interest are ... 

Many organisms are exposed to some of the thermal, chemical, and physical stresses of entrainment by being mixed at the discharge with the heated water this is plume entrainment. The exact number exposed depends on the percentage of temperature decline at the discharge that is attributed to turbulent mixing rather than to radiative or evaporative cooling to the atmosphere. 

Plume Containment. WeUs can be placed at a contaminated site to prevent the contamination from spreading further or migrating offsite. In the past, containment efforts often reHed on physical methods such as bentonite slurry trenches, grout curtains, sheet pilings, weU points, and fixative injections. Containment by judiciously placed weUs generally costs less, takes less time to install, and is more flexible because pumping rates and locations can be varied. 

Ejfective Height of an Emission The effective height of an emission rarely corresponds to the physical height of the stack. If the plume is caught in the turbulent wake of the stack or of buildings in... 

The lowering below the stack top of pieces of the plume by the vortices shed downwind of the stack is simulated by using a value h in place of the physical stack height h. This is somewhat less than the physical height when the stack gas exit velocity is less than 1.5 times the wind speed u,... 

Limits on emissions are both subjective and objective. Subjective limits are based on the visual appearance or smell of an emission. Objective limits are based on physical or chemical measurement of the emission. The most common form of subjective limit is that which regulates the optical density of a stack plume, measured by comparison with a Ringelmann chart (Fig. 25-1). This form of chart has been in use for over 90 years and is widely accepted for grading the blackness of black or gray smoke emissions. Within the past four decades, it has been used as the basis for "equivalent opacity" regulations for grading the optical density of emissions of colors other than black or gray. 

The jet-plume model only simulates vertical jets. Terrain is assumed to be flat and unobstructed. Application is limited to surface roughness mush less than the dispersing layer. User experti.se is required to ensure that the selected runtime options are self-consistent and actually reflect the physical release conditions. Documentation needs improvement there is little guidance... 

Zddovich, Y. B. 1937. Fundamental principle.s for free convective plume.s. Journal of Experimental and Technical Physics, vol. 7, no. 12. 

The first essential step in the design of a fume control system and selection of gas-cleaning equipment is the characterization of the fume emission source. Design procedures which can be used for new and existing industrial plants follow. The characterization of fume emission sources includes parameters such as plume flow rates (mVs), plume geometry (m), source heat flux (J/s), physical and chemical characteristics of particulates, fume loadings (mg/m ), etc. 

For a new process plant, calculations can be carried out using the heat release and plume flow rate equations outlined in Table 13.16 from a paper by Bender. For the theory to he valid, the hood must he more than two source diameters (or widths for line sources) above the source, and the temperature difference must be less than 110 °C. Experimental results have also been obtained for the case of hood plume eccentricity. These results account for cross drafts which occur within most industrial buildings. The physical and chemical characteristics of the fume and the fume loadings are obtained from published or available data of similar installations or established through laboratory or pilot-plant scale tests. - If exhaust volume requirements must he established accurately, small scale modeling can he used to augment and calibrate the analytical approach. 

For an existing process plant, the designer has the opportunity to take measurements of the fume or plume flow rates in the field. There are two basic approaches which can be adopted. For the first approach, the fume source can be totally enclosed, and a temporary duct and fan system installed to capture the contaminant. For this approach, standard techniques can be used to measure gas flow rates, gas compositions, gas temperatures, and fume loadings. From the collected fume samples, the physical and chemical characteristics can be established using standard techniques. For most applications, this approach is not practical and not very cost effec tive. For the second approach, one of three field measurement techniques, described next, can be used to evaluate plume flow rates and source heat fl uxes. 

The effective height of an emission rarely corresponds to tlie physical height of tlie source or the stack. If tlie plume is caught in tlie turbulent wake of tlie stack or of buildings in the vicinity of tlie source or stack, tlie effluent will be mixed rapidl) downward toward the ground. If the plume is emitted free of these turbulent zones, a number of emission factors and meteorological factors influence tlie rise of the plume. 

Important issues in groundwater model validation are the estimation of the aquifer physical properties, the estimation of the pollutant diffusion and decay coefficient. The aquifer properties are obtained via flow model calibration (i.e., parameter estimation see Bear, 20), and by employing various mathematical techniques such as kriging. The other parameters are obtained by comparing model output (i.e., predicted concentrations) to field measurements a quite difficult task, because clear contaminant plume shapes do not always exist in real life. 

More specific results are beyond the scope of our limited presentation for plumes. However, we will examine some gross features of transient plumes namely (a) the rise of a starting plume and (b) the dynamics of a fire ball due to the sudden release of a finite burst of gaseous fuel. Again, our philosophy here is not to develop exact solutions, but to represent the relevant physics through approximate analyses. In this way, experimental correlations for the phenomena can be better appreciated. 

As it was shown before that the wastewater plume spreads mainly in the upper fresh/brackish layer of the estuary [6], the difference between biotransformation rates in the two water layers is explained by a better pre-adaptation of the brackish water bacteria to A9PEO in their natural habitat, due to higher pre-exposures. It seems that the bacterial populations in these two physically very close habitats are quite different. 

The physical transport of dissolved organic compounds through the subsurface occurs by three processes advection, hydrodynamic dispersion, and molecular diffusion. Together, these three cause the spread of dissolved chemicals into the familiar plume distribution. Advection is the most important dissolved chemical migration process active in the subsurface, and reflects the migration of dissolved chemicals... 

Physical containment Physically contains contaminant plume with use of cutoff walls, caps, liners, etc. Site specific Limited in depth... 

We now have an expression for c x, y, z) that depends on the parameter 8, which itself depends on time. The quantity m8 expresses the distance for which a puff emitted at / = 0, and whose center is located at x = iit, has appreciable concentrations. Physically, Eq. (4.9) expresses the concentration emanating from the point source to be a plume composed of many puffs whose concentration distributions are sharply peaked about the puff centroids at all travel distances. We have not specified the parameter 8, although we expect that it should be proportional to aixlu)(u. The assumptions made in deriving Eq. (4.8) require that 8 < xlu. If the proportionality constant relating 8 and aix/u)/u is of order one, as we expect it to be, then the condition of validity of Eq. (4.9) can be stated as... 

Physically, this condition states that the spread of the individual puffs is small compared to the downwind distance. An alternative way of expressing this condition is that the rate of spreading of a puff in the direction of the mean flow is small compared to the rate of advection of the puff by the mean flow. This assumption is termed the slender-plume approximation. 

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