FLUID MODELING OF DENSE GAS DISPERSION OVER A RAMP

The basic nature of the transport and dispersion of a dense gas plume in the simulated neutral atmospheric boundary layer of a wind tunnel was investigated, both in flat terrain and over a ramp. For the particular value of the buoyancy parameter used in these experiments, the plume buoyancy was significant; the resulting dense plume was significantly wider in the lateral direction and much narrower in the vertical direction, yet the longitudinal ground-level concentration profile downwind was essentially identical to that from the neutral plume. The lateral concentration profiles of the neutral plumes were essentially Gaussian in character, whereas the dense gas plumes exhibited top-hat distributions for considerable distances from the source. The net effect of the ramp on the dense gas plume was a small reduction in ground-level concentration (less than a factor of two, even for a source relatively close to the base of the ramp). This reduction was quite similar to that observed for the neutral plume.