Physical simulation of a single-celled tornado-like vortex, Part B: Wind loading on a cubical model

A tornado vortex simulator was used to generate a single-celled tornado-like vortex whose flow field was presented and compared with available data from tornadoes recorded in Manchester and Spencer, South Dakota, both rated F4 on the Fujita scale, as described in Part A. A 30 mm cubical model, scale ∼1:3500, was placed at various locations relative to the vortex core and pressure measurements were obtained in order to determine wind loading. Results show that a permeable building (a building interior that experiences the local barometric pressure conditions caused by the tornado) subjected to this tornadic flow field experiences positive pressures on more than one face and that completely opposite forces (pressure as opposed to suction) can arise when comparing the same model in an atmospheric boundary layer flow at equivalent horizontal angles of attack of the approaching wind. These distinctly different distributions between tornado-like vortex and atmospheric boundary layer flows demonstrate the need for separate studies to be conducted on building structures under tornadic wind loading.