Recent progress in modeling the atmospheric dispersion of heavy gases over variable terrain using the three-dimensional conservation equations

Conference · Mon Aug 01 04:00:00 EDT 1983

OSTI ID:5763210

Chan, S. T.; Ermak, D. L.

In this paper, a three-dimensional, conservation equation model for simulating the atmospheric dispersion of heavy gases has been briefly described; the model was successfully applied and assessed via simulating three distinctly different LNG spill experiments. These experiments involve approximately 30 m/sup 3/ LNG spills, with atmospheric conditions ranging from slightly stable to slightly unstable (ambient wind speed from about 2 m/s to 10 m/s). In general, good agreement between model predictions and field measurements was observed in all cases based on comparing, among others, the maximum concentrations as a function of downwind distance, the maximum downwind distances to the LFL, time histories of concentration at specific locations, and concentration contours on certain horizontal and crosswind surfaces. In particular, the overall results obtained in the model calculations with the simulated actual topography were shown to correlate much better with the field data in that many important features of the vapor cloud observed under the light wind conditions of Burro 8 were successfully reproduced. These include the spreading of vapor cloud in all directions (in upwind direction as well), the vortex-induced high concentration regions, the bifurcation of the NG cloud, and the deflection of the NG cloud due to sloping terrain. Through the present numerical simulations, the effects of variable terrain on the dispersion of heavy gases have been clearly demonstrated. Even with the relatively mild terrain at the test site and under a moderately high wind speed of approx. 6 m/s (Burro 9), the resulting vapor cloud dispersion was seen to differ noticeably from that using a flat terrain assumption. The combined effects of large gravity-flow (relative to the mean wind) over variable terrain and under light wind conditions (Burro 8) were shown to be even more profound. In such gravity-flow dominated regimes, proper treatment of the terrain, if present, is obviously necessary.

• Research Organization: Lawrence Livermore National Lab., CA (USA)
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 5763210
• Report Number(s): UCRL-88495; CONF-830802-2; ON: DE83016940
• Country of Publication: United States
• Language: English

Related Subjects

03 NATURAL GAS
030800* -- Natural Gas-- Environmental Aspects
500200 -- Environment
Atmospheric-- Chemicals Monitoring & Transport-- (-1989)
54 ENVIRONMENTAL SCIENCES
CLOUDS
DATA
DISTRIBUTION
ENERGY SOURCES
ENVIRONMENTAL TRANSPORT
EXPERIMENTAL DATA
FIELD TESTS
FLUIDS
FOSSIL FUELS
FUEL GAS
FUELS
GAS FUELS
GAS SPILLS
GASES
INFORMATION
LIQUEFIED GASES
LIQUEFIED NATURAL GAS
MASS TRANSFER
MATHEMATICAL MODELS
NATURAL GAS
NUMERICAL DATA
PLUMES
SPATIAL DISTRIBUTION
TESTING
THEORETICAL DATA
THREE-DIMENSIONAL CALCULATIONS
TOPOGRAPHY
WIND