Effects of stable stratification on flow and dispersion around a cube

The first stages of a study on the effects of stable stratification on the flow and dispersion around a cube immersed in simulated atmospheric boundary layers are described. A brief overview of the tunnel arrangements and simulation devices is given and the instrumentation techniques are also discussed. Two boundary layers were used, a neutrally stable layer of depth about 1000mm and a moderately stable layer of depth around 450mm. The stable layer had a Monin-Obukhov depth of around 170mm. With the cube present mean and turbulent velocities were measured together with mean ground level concentrations. In the near-wake region it was found that stability was of little importance and the flow characteristics could be explained by reference solely to the upstream velocities and turbulence levels at the cube height. Further downstream differences in the behaviour of the velocity excesses and turbulence levels were apparent. However mean ground level concentrations were not found to differ greatly between the two layers.