Numerical study of flow structure and pedestrian-level wind comfort inside urban street canyons

In this work, the flow conditions are numerically investigated inside uniform and non-uniform street canyons well within the atmospheric boundary layer. The numerical simulations use the steady-RANS method with the near-wall modelling approach to simulate wall roughness at the boundary. With the aim of investigating both flow structure in broad terms and pedestrian comfort in the street canyon between parallel buildings, we test different canyon configurations with varied street width, building width and building height. Turbulent conditions are broadly expected to hold within the physically realistic range of Reynolds number of order 106 considered here, where we take the building height to be a characteristic length scale and the free stream velocity as the characteristic velocity. In addition to discussing the features of the canyon and wake flow, we investigate the effects of canyon geometry on pedestrian comfort by using the Extended Land Beaufort Scale for this purpose. We present and compare pedestrian comfort ‘maps’ for each of our geometries.