High cost and site-specific results of field experiments have made water channels and wind tunnels important tools for the investigation of urban air quality. However, the applicability of laboratory studies depends on the correct scaling of the dominant physical properties. Simulation of the urban dispersion problems in laboratory facilities requires correct scaling of flow, plume rise, and dispersion. In this paper, an alternative method for scaling the urban dispersion parameters in water channels and wind tunnels is presented. Water channel experiments show that plume rise associated with relatively low-level buoyant sources in urban areas is highly affected by the complex flows induced by the surrounding buildings and currently used plume rise models are not able to reproduce it accurately. Based on these experiments, a different method for scaling plume rise in urban areas, which accounts for the effect of surrounding buildings, is developed. The similarity of flow and plume rise, by matching the densimetric Froude number and relaxing initial conditions at the source, enables correct scaling of the concentration measurements from the laboratory to the field through the non-dimensional Gaussian dispersion model. This new technique allows us to investigate the dispersion of buoyant emissions from low-level sources in urban areas through water channel or wind tunnel simulations.

Results from water channel measurements of plume rise and a sensitivity study on the newly proposed scaling method will be presented.