Examining the generation of peak and fluctuating pressures in a two-dimensional separating-reattaching flow on a blunt prismatic prism

This project sought to obtain almost full-scale wind flow and pressures over a generic bluff body – prism - to validate more than 50 years of obtaining wind loads on tall buildings from very small models at reduced wind speeds in boundary layer wind tunnels. Differences between model- and full-scale are known as Reynolds Number effects in the field of Wind Engineering.

Tests were carried in the NHERI FIU Wall-of-Wind (WoW) facility on a blunt prismatic prism that generated a separation bubble under which the highest wind suctions are known to be generated. A substantial part of the project became generating stable, consistent and repeatable flow fields at very high wind speeds (~50m/s) and for two types of turbulent flow – smooth (low turbulence) and turbulent (~14%) consistent with full scale situations.

Pressure distributions beneath the separation bubble as a function of Reynolds Number and turbulence parameters, intensity, and scale, were obtained and demonstrated some dependence on the actual wind speed, even for this sharp-edged prismatic shape. Preliminary PIV measurements of the flow field around the prism were attempted with a new and novel system purchased for the WoW facility, late in the life of this project. These measurements indicated that it may be possible to pursue these studies at very high Reynolds Number (high speed) despite the difficulties of working in natural lighting and sufficient seeding of the flow field in the Wall-of-Wind facility.