Development of an Atmospheric Dispersion Model for Heavier-Than-Air Gas Mixtures. Volume 2. Laboratory Calm Air Heavy Gas Dispersion Experiments.
Final rept. Sep 80-May 85,
ARKANSAS UNIV FAYETTEVILLE DEPT OF CHEMICAL ENGINEERING
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Laboratory experimental instantaneous releases of right circular cylindrical volumes of heavy gas Freon-12air 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 16 powersq 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 cum Freonair 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.
- Civil Engineering
- Fluid Mechanics