Models plume rise

One major item remains before we can apply the dispersion methodology to elevated emission sources, namely plume height elevation or rise. Once the plume rise has been determined, diffusion analyses based on the classical Gaussian diffusion model may be used to determine the ground-level concentration of the pollutant. Comparison with the applicable standards may then be made to demonstrate compliance with a legal discharge standard. 

Thus, based on the above, it is not surprising that even under the best conditions an uncertainty factor of approximately 2 is likely in estimates of the plume rise. Despite this somewhat pessimistic introduction, estimations of plume rise are worthwhile and an integral part of the dispersion analysis. Table 2 presents some of the well-known plume rise formulas used in different model approaches. The two major controlling variables which appear in many, if not all, of the plume rise formulas surveyed are ... 

The SCREEN model calculates plume rise for flares based on an effective buoyancy flux parameter. An ambient temperature of 293° K is assumed in this calculation and therefore none is input by the user. It is assumed that 55 percent of the total heat is lost due to radiation. 

The use of the methods of Briggs to estimate plume rise are relied on in the SCREEN model. Stack tip downwash is estimated following Briggs (1973, p.4) for all sources except those employing the Schulman-Scire downwash algorithm. Buoyancy flux for non-flare point sources is calculated from ... 

ISC-PRIME - Industrial Source Complex - Plume Rise Model Enhancements-. ISC-PRIME dispersion model is being evaluated as the next generation building downwash model. This version of the ISC model has a new set of algorithms and has been named ISC-PRIME. The files below are made available for review and evaluation only, but you can get some insight into how they work and the types of applications ... 

PRIMPLDN.PDF 589 KB 10/25/99 (Draft Development and Evaluation of the PRIME Plume Rise and Building Downwash Model)... 

Leahey, D.M. and M.J.E. Davies, 1984. Observations of Plume Rise from Sour Gas Flares. Atmospheric Environment, 18, 917-922. Misra, P.K. and S. Onlock, 1982. Modelling Continuous Fumigation of Nanticoke Generating Station Plume. Atmospheric Environment, 16, 479-482. 

Meteorology plays an important role in determining the height to which pollutants rise and disperse. Wind speed, wind shear and turbulent eddy currents influence the interaction between the plume and surroimding atmosphere. Ambient temperatures affect the buoyancy of a plume. However, in order to make equations of a mathematical model solvable, the plume rise is assumed to be only a function of the emission conditions of release, and many other effects are considered insignificant. 

For a given release scenario, estimate the state of the released contaminant after it has depressurized and become airborne (including any initial dilution). The initial mole fraction of hazardous components will be applied to the final reported concentrations and hazardous endpoint concentrations throughout the process. If source momentum is important (as in a jet release or for plume rise), other models are available that can address these considerations. Disregarding the dilution due to source momentum will likely result in higher concentrations downwind, but not always. 

Models to Allow for the Effects of Coastal Sites, Plume Rise, and Buildings on Dispersion of Radionuclides and Guidance on the Value of Deposition Velocity and Washout Coefficients, Fifth Report of a Working Group on Atmospheric Dispersion, National Radiological Protection Board, NRPB-R157, 1983. 

Schatzmann, M. (1979) An integral model of plume rise, Atmos. Environ. 13, 721-731. 

Maity formulas have been devised to relate the chimney and the meteorological parameters to the plume rise. The most commonly used model, due to Briggs, will be discussed in a later section. The plume rise that is calculated from the model is added to the actual height of the chinmey and is termed the effective source height. It is this height that is used in the concentration prediction model. 

Two types of dispersion models are used to describe these releases when the puff or plumes are neutrally or positively buoyant. When there is an instantaneous release or a burst of material, we make use of a puff model. In this model the puff disperses in the downwind, cross wind, and vertical directions simultaneously. Computer codes written for puff models usually have the capability of tracking multiple puff releases over a period of time. When the release rate is constant with time, the puff model can be mathematically integrated into a continuous model. In this case, dispersion takes place in the cross wind and vertical directions only. The mathematical expressions are those discussed in Section III. The dispersion coefflcients used, however, may differ from those described in Section IV. Plume rise equations from Section V for positively buoyant plumes may be used in conjunction with these dispersion models. The equations of current models indicate that they are well formulated, but the application of the models suffers from poor meteorological irrformation and from poorly defined source conditions that accompany accidental releases. Thus, performance of these models is not adequate to justify their use as the sole basis for emergency response planning, for example. 

Jones, J.A. (1983). Models to allow for the effects of coastal sites, plume rise and buildings on dispersion of radionuclides and guidance on the value of deposition velocity and washout coefficients. National Radiological Protection Board, Harwell Report NRPB-R157. 

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. 

Vol. 25 B. Hederson-Sellers Modeling of Plume Rise and Dispersion -The University of Salford Model U.S.PR. 

The classic Gaussian plume model discussed above assumes that density differences between a chemical-containing plume and the surrounding air either can be neglected or can be accounted for by a small amount of plume rise or plume tilt. This condition is sometimes referred to as passive dijfusion. When gases or vapors are significantly denser than air, however, both gravity and wind affect chemical transport. 

Plume height is based on the assumed F stability and 2.5 m/s wind speed, and the dispersion parameter (o, ) incorporates the effects of buoyancy induced dispersion. If x , is less than 200 m, then no shoreline fumigation calculation is made, since the plume may still be influenced by transitional rise and its interaction with the TIBL is more difficult to model. 

Lassiter JC, Hauri EH (1998) Osnhum-isotope variahons in Hawaiian lavas evidence for recycled oceanic lithosphere in the Hawaiian plume. Earth Planet Sci Lett 164 483-496 LaTourrehe TZ, Kennedy AK, Wasserbuig GJ (1993) Thorium-uraiuum frachonation by garnet evidence for a deep source and rapid rise of oceanic basalts. Science 261 739-742 Liu M, Chase CG (1991) Evoluhon of Hawaiian basalts a hotspot melhng model. Earth Planet Sci Leh 104 151-165... 

Figure 12.16 Plume front rise-time simulated by saltwater modeling [24,25]...

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