Large eddy simulation of flow and pollutant dispersion in a street canyon: analysis of performance of various inflow turbulence generation techniques

The objective of the present study is to analyze the influence of various inflow turbulence generation techniques (ITGT) on the flow field and pollutant dispersion around a street canyon with perpendicular wind flow through the large eddy simulation approach. Vortex method (VM), internal mapping (IM), spectral method (SM) and no fluctuations (NF) are the four ITGTs under investigation. Results suggest that ventilation of the canyon is mainly due to corner eddies, canyon vortex and the flow passing over the top of the buildings. All ITGTs can capture the two important structures of canyon vortex and corner eddy, but IM underpredicts the corner eddies and SM and NF underpredict the canyon vortex. VM slightly overpredicts the canyon vortex. However, its accuracy in predicting the pollutant dispersion at both walls and low speed regions is higher than the other methods. The velocity fluctuation is also another important parameter for ventilating the low speed regions. The VM displays the most accurate results, and the NF shows the least accurate ones. In terms of relative error, computational cost, and the number of required input parameters, VM is the most optimized ITGT.