Influence of Inflow Boundary Conditions on Pollutant Dispersion in Large Eddy Simulation

Prediction accuracy of pollutant dispersion around a cubic building with a flush vent located on its roof was examined using various inflow boundary conditions for the Large Eddy Simulation and results were compared with wind-tunnel data. Three types of inflow conditions, namely, Quasi-laminar, Vortex method and Spectral Synthesizer were examined in the present work. All the inflow conditions showed fairly good predictions for the streamwise direction of contaminant dispersion on the roof whereas for spanwise direction, leeward wall and side walls, the results deviated somehow from the experimental data. In addition, at the side and leeward surfaces of the building all inflow boundary conditions overestimated the concentration distribution, which was mostly due to the isotropic subgrid scale stress model and subgrid scale flux molding beside of the boundary condition. The results demonstrated that Quasi-laminar method provided better agreement with experimental data concerning the prediction of dispersion in the ground level of the wake region. However, in order to evaluate the accuracy of the inflow boundary condition, other parameters such as Strouhal number and turbulence budget need further attention. Finally, it is concluded that the crucial role ofthe boundary condition in the LES prediction accuracy should be taken into consideration in any CFD study applying this interesting but risky approach

Keywords:

Inflow conditions , Inflow boundary condition , LES , gas dispersion