Analytical Dispersion Model Research Articles

The MRBT model: an analytical dispersion model in a finite mixing layer. Sensitivity analysis and validation against tracer measurements

This paper describes the characteristics of the MRBT model for studying the dispersion of a pollutant in the lower atmosphere under conditions of spatial homogeneity. The MRBT is shown to be a simple and efficient model based upon a non-stationary analytical solution of the atmospheric dispersion equation in a finite mixing layer. The results of the sensitivity analysis and of validation testing, made with field measurements of tracers carried out at the Nuclear Research Centre in Karlsruhe (Germany), demonstrate the superiority of MRBT with respect to traditional Gaussian models. The model is currently implemented in FORTRAN 77 for the personal computer and is suitable for an initial assessment of short-term atmospheric dispersion with limited computing resources.

Footprint estimation for scalar flux measurements in the atmospheric surface layer

The flux footprint is the contribution, per unit emission, of each element of a surface area source to the vertical scalar flux measured at height z m ; it is equal to the vertical flux from a unit surface point source. The dependence of the flux footprint on crosswind location is shown to be identical to the crosswind concentration distribution for a unit surface point source; an analytic dispersion model is used to estimate the crosswind-integrated flux footprint. Based on the analytic dispersion model, a normalized crosswind-integrated footprint is proposed that principally depends on the single variable z/z m , where z is a measure of vertical dispersion from a surface source. The explicit dependence of the crosswind-integrated flux footprint on downwind distance, thermal stability and surface roughness is contained in the dependence of z on these variables. By also calculating the flux footprint with a Lagrangian stochastic dispersion model, it is shown that the normalized flux footprint is insensitive to the analytic model assumption of a self-similar vertical concentration profile.

Traffic co-dispersion pattern in Kuwait

Carbon monoxide due to vehicular traffic is one of the potential hazards in Kuwait. Co-dispersion studies at three business-cum-residential areas of Mansourya, Rabiya and Riqqae have been undertaken. A comparative study of carbon monoxide concentrations due to vehicular traffic in Kuwait has been made by using an analytical dispersion model (IITCO) and the Intersection Midblock Model (IMM). While IITCO has been developed at IIT Delhi, India, the other is an operational model in the U.S. The dispersion parameters are formulated in terms of relevant turbulence quantities during daytime when convective mixing is a dominant feature. Meteorological parameters to be used in the model have been compiled from the meteorological observatory in Kuwait for the months of July, August and September 1986. Model results compare well with observations.

Radionuclide dispersion after core-concrete melt leaching by groundwater / Ausbreitung von Radionukliden nach der Auslaugung einer Kernmaterial-Beton-Schmelze durch Grundwasser

In this paper, the amounts of some radionuclides leached out by the passing groundwater are estimated. The transport of dissolved radionuclides in groundwater is simulated by an analytical dispersion model; the underlying parameters are the hydrogeological characteristics of the Upper Rhine Valley. Simple models are used to estimate the ensuing radiation exposures for various exposure pathways

Predicted and measured concentrations of traffic carbon monoxide over Delhi

Carbon monoxide concentration due to vehicular traffic in urban Delhi has been computed by using an analytical dispersion model (IITCO), Pollution Episodic Model (PEM) and Intersection Midblock Model (IMM). While IITCO has been developed in IIT, the other two are operational models in the U.S.A. Computations from models are compared with observations collected at ITO, Janpath, Nazafgarh and Townhall. On-site measurements of CO are taken by using real time analyzers and meteorological parameters are obtained from a micrometeorological tower at IIT Delhi. The model results compare well with observations. The performance of IITCO is compared with PEM and IMM and found to be quite satisfactory. The diurnal variation of concentration is also found to be in good agreement with the diurnal variation of traffic volume.

Bhopal gas tragedy: Model simulation of the dispersion scenario

In this paper, we present and analyse various aspects of the leak of toxic gas from the Union Carbide Plant at Bhopal, India in December 1984. The physicochemical properties of the deadly methyl isocyanate (MIC) and its biological activity, as well as the probable causes of the accident, are discussed. The role of meteorology and topography with regard to the dispersion process is also documented. To obtain an estimate of the possible concentration levels of MIC in the atmosphere, an analytic dispersion model has been formulated. The model output gives an estimate of the ground level concentration and the approximate time of arrival of the plume front in the various affected localities. Dry deposition and the aqueous phase conversion of MIC with the humid atmosphere were also featured in the model. The model results seem to be fairly well correlated with the scantily available mortality distribution records. Finally, the paper ends with descriptions of the disastrous effect of the gas on animals, plants and humans.

Comparison of four analytical dispersion models for near-surface releases above a grass surface

The results of a new model called ‘Pasquill-Businger’-model, and three Gaussian plume models with different diffusion parameters stemming from, (a) the U.S. Nuclear Regulatory Guide 1.145 (1982), (b) the Western German Regulatory Guide TA-Luff (1983), (c) Klug (1969, Staub-Reinhaltung der Luft 29, 143–147), are compared with 23 experiments of the Prairie-Grass Project (Barad, 1958, Geophys. Res. Pap. 59, AFCRC-TR-58-235). The new model uses the solution of the diffusion equation given by Berlyand (1975, NERC, USEPA), the exchange coefficient for vertical diffusion, K 2, from Businger et al. (1971, J. atmos. Sci. 28, 181–189), and Pasquill's (1976, EPA-600/4-76-030 B) relation for σ y . The new model is superior to the others since it uses power functions for wind velocity and vertical diffusion and is independent of the definition of stability classes.

An analytical dispersion model for sources in the surface layer

A two-dimensional model, based on an analytical solution of the diffusion equation in a shear flow, is validated by comparison with cross-wind integrated concentrations of Prairie-Grass experiment. The wind velocity and eddy diffusivity power law profiles, defined respectively by exponent α and β, are determined by fitting log-linear profiles using both Businger and Dyer flux-profile relationships. They result to depend on the vertical plume spread which is a function both of the stability and of the distance from the source. The model, with Dyer's parametrization, fits the data quite well, except for very unstable conditions.

DISPERSION MODELING OF MULTIPLE SOURCES USING THE HP‐41CV

Abstract. WMPLUME is an analytic dispersion model based on the Wilson and Miller equation presented here in a program for the HP‐41CV handheld, programmable calculator, the HP‐41CX, or the HP‐41C with four memory modules. The user specifies the spacing and extent of the field of observation points. The calculator can handle up to 36 fully penetrating, continuous injection well sources or a lesser number of discontinuous wells. The time of observation can be changed easily and sources can be added or deleted readily. The code is prepared for use with or without a printer attached to the calculator.

ANALYTICAL AND CFD INVESTIGATION OF TURBULENT DIFFUSION MODEL FOR PARTICLE DISPERSION AND DEPOSITION

A 2D analytical turbulent diffusion model for particle dispersion and deposition at different heights across the pipe flow and circumferential deposition has been developed. This liquid-solid turbulent diffusion model presented in this paper has emanated from an existing gas-liquid turbulent diffusion model. Simultaneously a comprehensive 3D numerical investigation has been carried out to study the above making of multiphase mixture model available in Fluent 6.1. In both studies different particles sizes and densities were used. The deposition was studied as a function of particle diameter, density and fluid velocity. The deposition of particles, along the periphery of the wall and at different depths, was also investigated. Both studies showed that the deposition of heavier particles at the bottom of the pipe wall was found to be higher at lower velocities and lower at higher velocities. The lighter particles were found mostly suspended with homogeneous distribution. Smaller particles were also suspended with marginal higher concentration near the bottom of the wall. This marginal higher concentration of the smaller particles was found to be slightly pronounced for lower velocity. The larger particles clearly showed deposition near the bottom of the wall. These analogies of particles are well discussed with the ratio between free flight velocity and the gravitational settling velocity. Key Words: Multiphase flow, turbulence diffusion, particle deposition, horizontal flow. doi: 10.3329/jme.v40i1.3472 Journal of Mechanical Engineering, Vol. ME40, No. 1, June 2009 39-53