PRESSURE FLUCTUATIONS ON THE ROOFS OF LOW-RISE BUILDINGS IN TURBULENT BOUNDARY LAYERS

摘要

Buildings are often exposed to the highly turbulent atmospheric boundary layer flows near the earth's surface. Roofs of low-rise buildings in particular are vulnerable to the resulting aerodynamic loads, especially during the extreme wind storms. For flat-roofed, low-rise buildings with relatively large plan dimensions, the approach flow separates at the leading edge of the roof and then reattaches creating a separation bubble. This separation bubble is a turbulent recirculating flow region that is responsible for causing large-magnitude uplift on the roof surface. Such large, uplifting forces can cause damage to the roofs and roof-mounted structures. There are a limited number of studies present in literature focussing on the flow field and pressure fluctuations on the roof surface of the low-rise buildings and its dependency on the turbulence properties in the incident boundary layer flows compared to the studies performed on two-dimensional bluff bodies in uniform upstream flows. In this paper, the effects of the turbulence intensities and length scales in the boundary layer flows on surface pressure fluctuations for two low-rise building models are examined. The results indicate that roof surface pressure fluctuations strongly depend on roof height turbulence intensity and length scales in the approaching boundary layer flows. At lower levels of turbulence intensities, turbulence scales of significantly higher order of magnitudes compared to the building heights play important roles in characterizing the distribution of surface pressure fluctuations.