Interaction of severe convective gusts with a street canyon

Severe convective gusts lead to wind conditions that differ from those of atmospheric boundary layer (ABL) flows. Main differences are high velocities at ground level and transient flow conditions. Their interaction with inner-city areas has only rarely been examined and is the aim of the present work. In the experimental study the convective gusts were simulated by a jet, imbedded in an ABL flow generated by a wind-tunnel. The gust impinged on a street canyon model. Both steady experiments (continuous jet) and non-steady experiments (pulsed jet) were conducted. Flow fields within the street canyon were measured by means of a 2D/2C TR-PIV system. Comparisons of the steady flow field within a street canyon model and for a gust propagation on open terrain revealed an average increase of the maximum horizontal velocity of 50% within the canyon, an increase of the outflow's height, and a conservation of high velocities over a distance more than 3 times larger compared to open terrain conditions. Further experiments with a transient gust included the generation of a ring vortex. This vortex propagates above the street canyon and results in an additional increase of peak velocities. (c) 2016 Elsevier B.V. All rights reserved.