Experimental evaluation of pedestrian-level winds.

摘要

The presence of tall buildings has in many cases created uncomfortable and dangerous wind conditions at pedestrian level. Here a successful simple methodology was established to evaluate pedestrian level winds in a built-up urban terrain. Experiments were conducted using a 1:300 geometric scale model of the University of Minnesota hospital complex (UOMHC) and its surroundings, known for their unpleasant wind conditions. The UOMHC model was exposed to an accurately simulated atmospheric boundary layer in the SAFL wind tunnel. The modeling criteria for wind tunnel simulation of atmospheric flows and the applicability of the simulation to the experimental study are presented and discussed.; The comparison between the available prototype data and the corresponding wind tunnel data showed in general good agreement for the two tested wind directions; west and northwest. Velocity measurements underneath Unit B indicated that the pedestrian access to the PWB and Unit B buildings is the worst location along the street for a door.; A combination of sand scour tests, fog flow visualization, and tests using the oil film technique was applied to determine the wind environment in the UOMHC model. Sand scour tests supplied contour lines for the relative wind speeds. The scour technique can be used to estimate wind speed. The results using fine sand indicated that the scour contours most closely reflect the mean wind speeds measured by hot-film anemometers close to the ground. Fog flow visualization allowed good insight into the movement of the airstream. The average direction of the wind at ground level was shown clearly by the oil film technique. All the three visualization techniques indicated high pedestrian level winds under Unit B.; The use of various combinations of wind barriers to alleviate the problems of pedestrian discomfort induced by wind effects at the UOMHC were proposed and investigated. The results of a barrier, installed as a canopy at Unit B, indicated its effectiveness in reducing the velocities at Unit B. The presence of the skyway system was found to be useful in alleviating pedestrian level winds.