Effect of Urban Morphology and an Upstream Tall Building on the Scale Interaction Between the Overlying Boundary Layer and a Street Canyon

The interaction of large- and small-scale velocity fluctuations between a street canyon flow and the overlying boundary layer, under the influence of a local morphological model and a single upstream tall building, is investigated. The experiments are conducted in a wind tunnel, using Stereoscopic Particle Image Velocimetry (S-PIV) and Hot-Wire Anemometry (HWA). The Proper Orthogonal Decomposition-Linear Stochastic Estimation (POD-LSE) method is applied to decompose the velocity fluctuation scales and estimate the large-scale fluctuations at a high frequency. The amplitude modulation mechanism, which was found to exist for both smooth and homogeneous rough wall boundary layers in previous studies, still applies to the more complex morphological model with a single upstream building having a relative low height, but with some modification. When the upstream building is much higher than the surrounding buildings, the large eddies shed from the tall building may predominate the scale interaction.