AN EXPERIMENTAL-STUDY OF 2-DIMENSIONAL ATMOSPHERIC GAS DISPERSION NEAR 2 OBJECTS

Two-dimensional gas dispersion in the atmosphere was investigated experimentally using an atmospheric boundary-layer wind tunnel. Argon gas, which is one and one half times heavier than air, was injected two-dimensionally and uniformly near two square objects at the rates of 3.55 and 4.93 m3/min per lateral meter from the bottom of the wind tunnel floor through a porous metal plate. The gas injection source was located at one object distance upstream of the first square object. Gas concentrations and velocities of the flow field were measured using an aspirating hot-film probe and a low velocity flow analyzer, respectively. The gas was dispersed no higher than approximately 2.0 object heights near the objects, and dispersed no higher than 3.5 object heights at the location of downwind distances of nine object lengths for the injection rates tested. The gas concentrations between the injection source and the first object were about 4 to 5 times higher than the gas concentrations of the other locations. The gas concentrations were 2 to 3% in the recirculation zone between the two objects, and were less than 2% behind the second object. The air-gas mixtures in the recirculation zone between the two objects and within the wake recirculation bubble behind the second object were well mixed and no gravitational settlement was detected in those regions. However, as the mixture moved down-stream, the gravitational settlement occurred beyond the wake recirculation bubble. This paper demonstrates that it is possible to model a two-dimensional heavy gas release in the atmosphere using wind-tunnel simulation with properly matched similitude parameters. © 1990 Kluwer Academic Publishers.