Mean pressure distributions and reattachment lengths for roof-separation bubbles on low-rise buildings

Abstract

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Effects of Freestream Turbulence on the Pressure Acting on a Low-Rise Building Roof in the Separated Flow Region

“…The results show that the spatial distribution of the peaks is heavily influenced by X R , confirming the functional relationship described in Akon and Kopp (2016). Further, we show that extreme suction under the separation "bubble" collapse if data are normalized by the mean reattachment length and the gust velocity pressure computed from a non-Gaussian peak factor estimator that accounts for the longitudinal turbulence intensity at eave height.…”

“…Tables 2 and 3 list values for the wide and narrow edge element orientations. Tables 2 and 3 show slightly smaller mean reattachment lengths when compared with X R values presented in Akon and Kopp (2016). The lower X R values might be a result of the lateral location (y/H) selected for the line transects.…”

“…Figure 11 presents the results for 16 terrains resulting from increasing the element height from 10-160 mm and rotating the elements in the wide (left column) and narrow (right column) orientation to the oncoming flow. In the absence of particle image velocimetry measurements to quantify the distance from the leading edge to the reattachment point (X R ), the empirical relationship developed by Akon and Kopp (2016) (Figure 8) was applied to estimate the value based on the longitudinal turbulence intensity (I u,H ). Tables 2 and 3 list values for the wide and narrow edge element orientations.…”

“…The lower X R values might be a result of the lateral location (y/H) selected for the line transects. In Akon and Kopp (2016), the pressure taps were located along the centerline of the roof surface. Larger mean reattachment lengths should be expected along the roof 's centerline.…”

“…The bubble's average extent, i.e., the mean reattachment length (X R ), is also sensitive to the aspect ratio of the building. For example, composite analysis of multiple BLWT studies by Akon and Kopp (2016) have shown that the mean reattachment length monotonically decreases from smooth terrain to nominally open exposure conditions, plateauing as the surface roughness increases.…”