Development of a k–ε model for the determination of air exchange rates for street canyons

A two-dimensional renormalized-group (RNG) k–ε turbulence model was developed to calculate the air exchange rate (ACH) of idealized street canyons. This model was validated against other modelling (large-eddy simulation, LES, and k–ε) and wind tunnel results. It was demonstrated that the current k–ε model was able to capture the complicated flow structures inside street canyons whose outputs agreed reasonably well with other modelling and wind tunnel results available in literature. This k–ε model was then applied to calculate the ACH for street canyons of aspect (building-height-to-street-width) ratios 0.5, 1.0, and 2.0. The values of ACH calculated by the current k–ε model compared favourably with those calculated by LES in which their differences were less than 20%. Moreover, there was a remarkable saving in computer resources and computation time by using the current k–ε model.