Stratified Shear Flows over a Simulated Three-Dimensional Urban Heat Island.
COLORADO STATE UNIV FORT COLLINS FLUID DYNAMICS AND DIFFUSION LAB
Pagination or Media Count:
Three-dimensional airflow over a rectangular heat island was studied for various conditions of approach flow in a wind tunnel. Three different thermal stratifications of the approach flow were selected for the study-neutral, ground based and elevated inversions. For each of these flows studies were conducted with and without roughness over the heat island and for the conditions with and without heating. Approach flow temperature profiles were modeled according to atmospheric data available in the literature. For each of the twelve cases mentioned above, measurements of mean wind velocity, longitudinal velocity fluctuations, mean temperature and temperature fluctuations were made. In addition, mean concentration measurements of a radio-active gas released from a two-dimensional, ground-level line source upwind of the heat island were made. Flow patterns were visualized for different cases with the help of a passive smoke source. Comparisons of data from the wind-tunnel measurements with the field data were made. The mechanisms of the heat island observed in the wind-tunnel for different stratified flows were very similar to those observed in the field. The urban heat island plume that passes aloft downwind causes an appreciable reverse flow onto the heat-island. The helical vortices at the edge of the heat island cause a reduction in the turbulence level resulting in high concentrations of the mass released from a continuous line source upwind of the heat island. Modified author abstract
- Atmospheric Physics
- Air Pollution and Control