The turbulence flow over a circular hill, having a cosine-squared cross-section and a maximum slope of about 32°, was investigated using split-fiber probes designed for measuring flows with a high turbulence and separation. Profiles of the means and variances for the three velocity components are presented and compared with those in the undisturbed (no- hill) boundary layer. The turbulent boundary layer separated behind the crest and reattached just at the lee foot of hill. The pronounced speed- up of flow occurs not only at the hilltop but also at the midway slope on its side. The maximum perturbations in the longitudinal and vertical velocity variances were observed at the height of hill (z/h=1), corresponding to the separated recirculating flow on the lee slope of the hill, while the maximum in the lateral velocity variance appeared at the height of z/h=0.125 beyond the hill, corresponding to the low-frequency motion in the wall layer.
The characteristics and structures of the pressure fields on the leading edge and corner regions of a low-rise building with a 4: 12-pitched roof have been investigated by using a data-base, which was constructed at BLWTL, The University of Western Ontario. An empirical formula for estimating the minimum pressure coefficient is provided based on a peak factor approach. For constructing the formula, the quasi- steady theory is applied to the evaluation of the rms pressure coefficients The application of this formula is examined by comparing the predicted results with the experimental ones. The relation between the spatial and time averages is discussed, regarding their effects on the peak pressure coefficients. Furthermore, a discussion is made of the performance of the AIJ Recommendations for Loads on Buildings (1993) for estimating the design wind loads on cladding of low-rise buildings.
Aerodynamic stability of long span bridges is usually investigated by wind tunnel tests. Due to the Reynolds number (Re) effect, however, different aerodynamic phenomena are sometimes observed between wind tunnel tests (Re: 103-105) and actual bridges (Re: 106-107). But there are a few studies discussing the aerodynamic phenomena in the range of 106≤Re≤107, because it is quite difficult to execute the full scale measurement of bridges. In this study the Reynolds number effect on the vortex shedding frequency (i.e. Strouhal number, St) was investigated using spectrum analyses and wavelet analyses of wind pressures acting on a deck measured at IKARA OOHASHI Bridge. The results showed that the St number observed at the bridge (Re≅106) were well corespondent with those observed by wind tunnel tests (104≤Re≤105).