NUMERICAL PREDICTION OF DISPERSION CHARACTERISTICS IN AN URBAN AREA BASED ON GRID REFINEMENT AND VARIOUS TURBULENCE MODELS

摘要

A detailed simulation of the Goettinger Strasse pollutant dispersion problem is performed using the CFD code CFX-TASCflow for different wind directions. Two turbulence models, the κ―ε and the RSM are adopted on three grid refinement levels. Besides the typical reference grid implemented by the TRAPOS group, two different grid resolutions are introduced. The first refinement is in the whole street canyon region on the x―y level, while the second one is local in all three directions. Validation of all involved computational schemes is performed based on relative available experimental data. The computed velocity fields and concentration contours imply that the typical reference grid is a suitable choice for the velocity fields, while local grid refinement in all three directions in a small region containing the receptor is required to upgrade the pollutant concentration results with modest additional computational effort. Finally the RSM model resulted in smaller concentration levels. The κ―ε model compared to the RSM seems a more appropriate choice to solve this particular problem.