Comparison between LES and standard k-ε model for flow within and above urban canyon under various thermal stratification

Abstract

Computational fluid dynamics （CFD） analysis using large-eddy simulation （LES） and standard k-ε modelThe results of LES and k-ε were compared with the wind tunnel experiment to investigate the prediction accuracy of CFD analysis. LES agreed with the wind tunnel experiment for the mean wind velocity and mean temperature. k-ε failed to reproduce the spatial distribution of the mean wind velocity and mean temperature within the urban canyon in unstable case. LES and k-ε agreed well with the wind tunnel experiment for the turbulent kinetic energy in stable case, although they underestimated it within the urban canyon in unstable case. k-ε also underestimated the Reynolds stress <u₁'u₃'> and turbulent heat flux <u₃'T'> within the urban canyon in unstable and stable cases. It is thought that the prediction accuracy of k-ε decreases because k-εunderestimates the exchange of momentum and heat within and above the urban canyon compared with LES and the wind tunnel experiment.