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Engineering and Technology

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Publication/Presentation Date



This report describes work that was done under AFOSR Contract Number FA9550-11-1-0056, studying the structure of a model urban boundary layer flow. The model geometry consisted of a set of plexiglass blocks, and the flow around this geometry was studied both experimentally as well as computationally. For the experiment, a Stereoscopic Particle Image Velocimetry (SPIV) method was developed that allows for a three-dimensional description of this urban flow, and helps gain insight into the characteristic flow structures in the streets and canyons of our model urban geometry. On the computational side, a new spectral-element code was developed that was demonstrated to produce accurate results, and can scale to thousands of processors on large high-performance computing systems. Good agreement between the experiment and computation was demonstrated. Most notably, wind tunnel experiments were performed at a number of different angles of incidence, providing for the first time a detailed overview of the effect of wind direction on the flow structures in the urban geometry. Valuable information about the flow structures are presented. The effects of incidence angles from 0 to 45 degrees of the incoming flow with respect to the urban array are investigated. A major observation from this work is that a strong channeling effect is observed for all incidence angles and is in agreement with that observed in other investigations for as little as 4 degrees. This channeling significantly affects the turbulence distribution within the array, the correlations between the various gust components and the structures responsible for contaminant transport.

Publication Title

Final Report


Air Force research Laboratory