Investigating low-frequency turbulence effects on building roof pressures through active flow control in a large boundary layer wind tunnel

Abstract

This study examines the effect of incident large-scale (low-frequency) turbulence on the wind pressure field acting on low-rise building roofs. Large-scale turbulence modulation was enabled by a high-performance 3 m × 6 m multi-fan array, termed Flow Field Modulator (FFM), situated at the upwind section of a large boundary layer wind tunnel (BLWT). The FFM was leveraged to actively generate low-frequency wind velocity fluctuations in the BLWT and operated in conjunction with a mechanized roughness element grid to simulate large- and small-scale turbulent atmospheric boundary layer flows. Aerodynamic pressure measurements were monitored on the surface of a 1:20 scale low-rise building model under multiple turbulent length scales and intensities. Experimental results demonstrate how, for similar turbulence intensity levels, higher correlation of pressure fluctuations in flow detachment zones are observed with increasing turbulent scales. Larger integral length scales were also linked to more pronounced non-Gaussian behavior (i.e., higher skewness) of local pressure signals in flow separation zones and along the path of conical vortices developed above the roof of the building model in the case of cornering wind azimuths. Finally, the study highlights how stronger non-Gaussian trends and increased pressure correlations lead to higher local and area-average peak suction roof loads.