LES of turbulent wind and gas dispersion in a city

We have conducted LES (large eddy simulation) for turbulent wind flows and dispersion of hazardous gas emitted from a point source on the ground in a large city, Tokyo. Also, for numerical validation, wind tunnel tests using a Dynamic Particle Image Velocimetry (DPIV) and tracer gas measurement system are performed to estimate turbulence statistics of wind and gas concentration in between the compacted tall buildings. We elucidate the predictive accuracy of LES based on the wind tunnel test data. Finally, we discuss the meaning and the potential of LES prediction for dispersion problems in a complex urban area, taking into consideration the limitation of the predicted results by Reynolds Averaged Navier–Stokes (RANS) modeling.