WIND-TUNNEL SIMULATION OF GAS DISPERSION OVER COMPLEX TERRAIN - COMPARISON OF 2 LENGTH-SCALE STUDIES

The effect of the length scale on wind-tunnel simulation is evaluated by comparing the results obtained from similar experiments performed i n two differently sized wind tunnels. One experiment was carried out i n the EPA (U.S. Environmental Protection Agency) meteorological wind t unnel (3.7 m wide, 2.1 m high and 18.3 m long). A similar study at a g eometrical scale reduced to 1:5 was performed at VKI (von Karman Insti tute) L-2B wind tunnel. Similar approaching flow (a simulated neutral atmospheric boundary layer), source characteristics and obstacle featu res were used. Three hill shapes were tested: a cone, a triangular rid ge with conical edges and a 2D triangular ridge. Mean velocity, stream wise turbulence intensity and concentration profiles (for three source heights) were measured, as in the reference study, and the compared r esults are presented. The normalized concentration values are comparab le in the two experiments and similar conclusions can be drawn from th e two scale experiments concerning plume behaviour with respect to the aspect ratio and the location of the maximal concentration values. Ho wever, the results are not fully conclusive about the scale effect.