Numerical study of turbulent flow fields in urban areas using modified k- ε model and large eddy simulation

In this study, a numerical urban model is proposed, which includes digital elevation model for topography, landuse database, digital maps on buildings and vegetation. Turbulent flow fields in the cube arrays with different packing densities and a real urban area are investigated by both modified k - epsilon model and large eddy simulation (LES). It is found that the simulation with the modified k - epsilon model is less sensitive with grid resolution and is able to predict turbulent flow fields over uniform urban-like cube arrays, where the turbulent flow fields are fully developed. However, the modified k - epsilon model shows some discrepancies between the predicted and measured turbulent flow fields in the urban area, where the flow fields are strongly affected by the organized motions generated by surrounding buildings. The LES model is able to predict turbulent flow fields in the uniform urbanlike cube arrays as well as in the non-uniform urban area. The accuracy of LES model strongly affected by the grid resolution and a grid dependency study is conducted in the target area.