Dynamics of internal pressures in tornado flow

Abstract

While understanding of external flows and pressures for tornadoes are improving, internal pressure behavior remains elusive. This study was performed with the intention to observe how internal pressures change as a tornado passes over a structure with a dominant opening, and determine whether Helmholtz resonator model is applicable for buildings immersed in tornado-like flow. Both scale model tests and a numerical study were performed to provide an insight into the behavior of internal pressures.

The results from this study indicate that generally, internal pressures for a building with a dominant opening are the result of a combination of the dynamic pressure acting on the opening, and the pressure trough of the vortex core, while buildings with a dominant opening are subjected to greater roof loads then buildings without a dominant opening. Comparisons of the measured pressures suggest that a Helmholtz resonator model is adequate for modeling internal pressures by producing similar pressures.

The experiment involved using the VorTech tornado simulator at Texas Tech University to obtain scale model pressure data from a building model with a dominant opening and background porosity, and comparing the results those produced by a numerical model.

Tornadoes are powerful and destructive phenomena that affect many people all over the world. They can generate some of the fastest wind speeds on the planet, and destroy very robust structures. Any structure with an opening under extreme wind conditions will experience a two pronged attack: external pressures generated by the flow over the building envelope, as well as internal pressures generated by the flow passing through one or more openings in the structure.