Aerodynamic characteristics of a high-rise building in a steady thunderstorm outflow-like flow field

Abstract

This paper investigates the aerodynamic characteristics of a high-rise building loaded by steady wind flows with different boundary layer profile shapes. The multiple-fan wind tunnel (MFWT) at Tamkang University was used to simulate a mean velocity field with a nose-shaped boundary layer profile, similar to that observed in thunderstorm outflows, and a standard boundary layer flow, both with 3–5% turbulence over the depth of the profile. A regular ‘open terrain’ boundary layer flow was also generated using spires and roughness blocks to enable comparison. Aerodynamic characteristics of the Commonwealth Aeronautical Advisory Research Council (CAARC) building loaded by each of these flow fields through a range of incidence angles were measured, analyzed, and compared. Results showed that pressures on the windward face of the building largely reflected the dynamic pressure in the incident wind field. Pressures on faces within the separated wake region were less easily explained. Incident mean velocity and turbulence profiles, as well as building orientation, were all found to influence measured wind loads and forcing spectra on these faces. Of particular interest was a significant reduction in cross-wind forcing observed in the simulated outflow-like winds, largely believed to occur because the lower elevation of strong winds in this profile limits the development of a separation vortex up the height of the building. It was also found that the estimated building response was almost universally lower in the outflow-like flow field when compared with the boundary layer cases.