Development of an Atmospheric Dispersion Model for Heavier-Than-Air Gas Mixtures
Development of an Atmospheric Dispersion Model for Heavier-Than-Air Gas Mixtures

Author: Jerry A. Havens

Publisher:

Published: 1985

Total Pages: 183

ISBN-13:

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Mathematical modeling techniques use to predict atmospheric dispersion of heavy gases are reviewed and critiqued. These dispersion processes are characterized by three phases: (1) near field, negative buoyancy-domainated flow regime; (2) intermediate field, stably stratified shear flow regime; and (3) far field, passive turbulent diffusion regime. Mathematical models of laboratory and natural gravity currents are used to describe the negative buoyancy-dominated regime flow and dilution processes. A laboratory investigation of instantaneous heavy gas releases in calm air demonstrates scaling from small release volumes (0.5 cu m) to large field (2000 cu m) field releases, and is used to develop a mathematical model for the buoyancy-dominated regime. Laboratory data from stratified shear flow mixing experiments are used to develop a model for vertical diffusion of heavy gases in the atmospheric surface layer. The model concepts are consistent with the limiting passive behavior of demonstrated air pollution models. An interactive computer model for heavy gas dispersion (DEGADIS) is developed. The DEGADIS model accounts for the three regimes of heavy gas dispersion processes and can be used to simulate instantaneous, steady state, and transient releases. The model provides predictions of downwind concentration decay which are in good agreement with the full range of field experimental data currently available, and is recommended for incorporation in the Coast Guard hazard assessment computer system.

Development of an Atmospheric Dispersion Model for Heavier-Than-Air Gas Mixtures. Volume 3. DEGADIS User's Manual
Development of an Atmospheric Dispersion Model for Heavier-Than-Air Gas Mixtures. Volume 3. DEGADIS User's Manual

Author: Jerry A. Havens

Publisher:

Published: 1985

Total Pages: 270

ISBN-13:

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The mathematical modeling techniques used to predict atmospheric dispersion of heavier-than-air gases discussed in Volume 1 are briefly summarized; these techniques are incorporated in an interactive computer model DEGADIS. Details of DEGADIS implementation are briefly discussed. The necessary input information to simulate a heavier-than-air gas release with DEGADIS is summarized. Example simulations of a steady state and transient release are included. A list of DEGADIS self-diagnostics with suggested actions are included. A listing of DEGADIS is included along with a partial list of program variables. Guidelines for installation of DEGADIS are presented.

Development of an Atmospheric Dispersion Model for Heavier-Than-Air Gas Mixtures. Volume 2. Laboratory Calm Air Heavy Gas Dispersion Experiments
Development of an Atmospheric Dispersion Model for Heavier-Than-Air Gas Mixtures. Volume 2. Laboratory Calm Air Heavy Gas Dispersion Experiments

Author: Jerry A. Havens

Publisher:

Published: 1985

Total Pages: 269

ISBN-13:

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Laboratory experimental instantaneous releases of right circular cylindrical volumes of heavy gas (Freon-12/air) with initial volumes ranging from 0.034 cu m to 0.531 cu m and specific gravities ranging from 2.2 to 4.2 are described. Releases with initial height-to-diameter ratios of 0.4, 1.0, and 1.57 are reported. The heavy gas flow field surrounding the release is described by time series of gas concentration at various radial and vertical coordinates with respect to release center. Measurements of the gravity current velocities are determined from time-of-onset of measured gas concentration. Calm-air instantaneous heavy gas releases are demonstrated to scale with a characteristic length cube root of V sub i where V sub i is the initial volume, and a characteristic time (V sub i to the 1/6 power)/(sq root of the reduced gravitational acceleration). The scaled laboratory releases predict the gravity-spreading and dilution process occurring during the buoyancy-dominated flow phase of the 2000 cu/m Freon/air instantaneous releases conducted by the British Health and Safety Executive at Thorney Island, UK. The gravity spread and dilution data are used to validate the buoyancy-dominated flow submodel which is incorporated in DEGADIS, the general purpose heavy gas dispersion model developed for the Coast Guard.

Development of Vapor Dispersion Models for Nonneutrally Buoyant Gas Mixtures-Analysis of TFI/NH3 Test Data
Development of Vapor Dispersion Models for Nonneutrally Buoyant Gas Mixtures-Analysis of TFI/NH3 Test Data

Author: Thomas O. Spicer

Publisher:

Published: 1988

Total Pages: 133

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Field-scale releases of pressurized anhydrous ammonia were performed by the Lawrence Livermore National Laboratories in 1983 for the U.S. Coast Guard, the Fertilizer Institute, and Environment Canada. Release rates for the four experiments ranged between 80 and 130 kilograms per second. The pressurized liquid ammonia jet formed a denser-than-air aerosol cloud. A method of determining the relative importance of jet and nonjet dispersion processes is discussed. The data from these experiments were analyzed to determine the mass flux of ammonia and the lateral and vertical concentration profile parameters for the cloud (sigma y and sigma z for the Gaussian plume model and SY and SZ for DEGADIS) at 800 meters downwind. These observed values of maximum concentration and concentration profile parameters were compared with DEGADIS and Gaussian plume model predictions. (DEGADIS is an atmospheric dispersion model designed to account for the influences of denser-than-air gases.) In addition, analysis of the experimental data indicated heat transfer to the aerosol cloud was insignificant although the cloud temperature was as low as -60 centigrade. (mjm).

Development of Vapor Dispersion Models for Nonneutrally Buoyant Gas Mixtures--Analysis of USAF/N2O4 Test Data
Development of Vapor Dispersion Models for Nonneutrally Buoyant Gas Mixtures--Analysis of USAF/N2O4 Test Data

Author: Thomas O. Spicer

Publisher:

Published: 1986

Total Pages: 103

ISBN-13:

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The Air Force is taking steps to improve and update safety procedures available for use during operations involving hazardous chemicals and fuels. In support of this effort, the Lawrence Livermore National Lab. conducted two field scale releases(Eagle 3 and 6) of nitrogen tetroxide (N2O4) at the Nevada Test Site during 1983. An analysis of the chemical interaction of N2O4 with the ambient humidity and oxygen is made. The reported source mass evolution rate is adjusted to account for these reactions; the source rate for Eagle 3 is between 2.9 and 3.1 kg/s, while for Eagle 6, the source between 1.6 and 1.7 kg/s. Reported nitrogen dioxide (NO2) concentrations downwind of the source are adjusted for the source mass evolution rate, and these observed conditions are compared with predicted concentrations using the Ocean Breeze/Dry Gulch model, the Pasquill-Hanna Gaussian plume model, and DEGADIS. (Developed for the Coast Guard, DEGAIS describes the negative buoyancy-driven flows and reduced vertical mixing observed for releases of heavier-than-air gases in the atmosphere. Observed Gaussian equivalent concentration profiles (sigmay and sigmaz) are also compared to predicted values. For these tests, the DEGAIS predictions are consistent with the observed concentration and values sigma y and sigma z, while the Gaussian plume models are not consistent. Furthermore, the importance of negative buoyancy-driven flows and decreased vertical mixing rates for Eagle 3 and 6 is predicted by a characteristic release Richardson number.

Energy Research Abstracts
Energy Research Abstracts

Author:

Publisher:

Published: 1994

Total Pages: 1032

ISBN-13:

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Semiannual, with semiannual and annual indexes. References to all scientific and technical literature coming from DOE, its laboratories, energy centers, and contractors. Includes all works deriving from DOE, other related government-sponsored information, and foreign nonnuclear information. Arranged under 39 categories, e.g., Biomedical sciences, basic studies; Biomedical sciences, applied studies; Health and safety; and Fusion energy. Entry gives bibliographical information and abstract. Corporate, author, subject, report number indexes.