Showing papers by "Rex Britter published in 1989"

Atmospheric dispersion of dense gases

Abstract: Public concern over the risks posed by the use of hazardous materials has grown markedly over the past decade. The dioxin release in Seveso (Italy) in 1976, that of methyl isocyanate in Bhopal (India) in 1984, and the liquefied petroleum gas explosions in Mexico City in the same year emphasized the possible scale of the tragedies that may accompany activi­ ties involving hazardous materials. The development of appropriate regulatory measures to achieve an ac­ ceptable balance between economic benefit and potential harm accom­ panying such activities requires quantitative assessment of the conse­ quences of the accidental release of material into the environment. It is commonly the case that hazardous industrial materials, be they flammable or toxic, produce a cloud, upon release into the atmosphere, that is denser than the environment. The information on dense-gas dispersion that is of interest to the hazards analyst is contained in the distribution of concentration as a function of the spatial coordinates and time. Very often, this information is required only in summary form, such as

Turbulent Diffusion Behind a Heated Line Source in a Nearly Homogeneous Turbulent Shear Flow

Abstract: The turbulent diffusion of heat from a line source has been examined in a nearly homogeneous turbulent shear flow with a uniform mean velocity gradient. Mean shear was generated in a wind tunnel using an array of parallel channels of transversely varying porosity. The dimensionless intensity of temperature fluctuations was found to decrease rapidly at large distances from the source, in agreement with the numerical predictions of a Lagrangian random walk model. Thus, it was confirmed that the shear tends to reduce the intensity of concentration fluctuations.

Modelling Dispersion from Accidental Releases

Abstract: Some physical processes relevant to the modelling of the dispersion of accidental releases of dense gases are noted. Observations on the structure of dense gas clouds are made, together with comments on mathematical modelling, physical modelling and the development of a workbook. The influence of buildings and topography are also considered.

Molecular and Stratification Effects on the Evolution of Concentration Fluctuations in Decaying Homogeneous Turbulence with Transverse Mean-Concentration Gradient

Abstract: Transport of a passive scalar contaminant in nearly isotropic non-decaying turbulence was first studied theoretically by Corrsinl, and in that study it was predicted that an imposed passive linear cross-stream mean temperature profile will maintain itself and will be independent of the downstream distance. Corrsin’s prediction of constancy of the cross-stream temperature gradient, s, has been confirmed experimentally for decaying turbulent flows2,3,4. Despite the constancy of s there has been confusing experimental data on the streamwise evolution of passive scalar contaminants. The heated grid method used by Wiskind2 to study the streamwise evolution of passive scalar has been found to be far from ideal because significant transverse variation of temperature variance was observed in Wiskind’s data3,4. The use of differentially heated screens downstream of a grid3,4 has aided the study of the streamwise evolution of passive scalar fluctuations, but there still remains some uncertainties in the physics of this type of flow particularly at large decay times.