High fidelity modeling of urban features

Results from an eddy-resolving DES computation and a RANS computation are presented for a model urban setting. Qualitative comparisons are made that show the additional structure of the DES solution due to resolved turbulence eddies. We observe that RANS models the general features of the farfield well; however, resolve the fine scale features of the flow in the immediate vicinity of the buildings requires LES (implemented here through the DES algorithm). DES proves a method to blend those approaches in a way that leverages the advantages of each. It uses RANS modeling in the farfield, not requiring too fine of a grid there, and switches to LES in the detached regions which are not captured well by RANS. This work is preliminary. It does, however, indicate that a DES approach is promising. We expect to explicitly model dispersion of a contaminant in the scenario in the near future. Ongoing work is directed at determining sensitivity to near-wall resolution and at determining simulation/modeling fidelity to flow physics. The results of this study are expected to help guide modeling work directed at urban dispersion.