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A LABORATORY SIMULATION OF TURBULENT CONVECTION OVER AN URBAN HEAT ISLAND
Citation:
Lu, J., S. Arya, W. Snyder, AND R.E. Lawson, Jr. A LABORATORY SIMULATION OF TURBULENT CONVECTION OVER AN URBAN HEAT ISLAND. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/A-92/231.
Description:
A systematic experimental study of the heat-island-induced circulation under turbulent conditions was conducted in the laboratory for an idealized, circular heat isalnd in an initially thermally stratified fluid (water) in a convection tank with no ambient flow. he primary objectives of this study were to obtain a better understanding of the mean and turbulent flow generated by the heat island and to identify the appropriate similarity parameters and scales for simulating such a flow. hree non-dimensional similarity parameters were derived from the governing equations of motion. hey are the convection Reynolds number Re = W*D/v, the Froude number Fr = W*/ND, and the Prandtl number Pr = v/a, where W* is the convective velocity scale, D is the heat-island diameter, v is the kinematic viscosity of the fluid, a s the thermal diffusivity and N is the Brunt-Vaisala frequency. he data indicate that at sufficiently large Re*, turbulent convection in the main flow becomes independent Re*, which is the basis of the laboratory simulation. he height of the heat-island top, Zi, is found to scale with W*N/gB, where B is the thermal expansion coefficient. hese measurements are also compared with field data from several cities and they agree with each other satisfactorily.