Development of a large-scale simulator
Mayer, Luke Joel
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A large-scale tornado simulator (largest in the U.S.A.) named VorTECH, was designed and constructed to gain insight into tornado-like vortices. Approximately two stories tall and 56 feet in diameter, the Ward-type simulator uses 64 airfoil columns to direct the airflow and eight suction fans on the top of the simulator to create the necessary updraft. It has the capability of producing vortices with inner core diameters of around three feet. A CNC hot wire foam cutter was used to fabricate the airfoil shapes and wood glue coatings were added to provide structural strength. The simulator was designed with the ability to have the aspect ratio adjusted by means of a movable ceiling. Features such as a viewing window, minimally intrusive velocity measurement system, pressure taps and a flow visualization channel were designed and built into the simulator. Initial measurements were preformed to better understand the capacities of this newly built simulator. Velocity measurements were made to calculate swirl ratio values at a simulator aspect ratio of 1. The swirl ratio is a measurement of the amount of rotation in the airflow and can be defined as the tangential velocity component divided by two times the radial velocity component. The aspect ratio is the ratio of the inflow height to the updraft region radius. Maximum swirl ratio values exceeded 4.9. Pressure taps were placed across the diameter of the updraft region and pressure distributions were measured for different airfoil configurations. The distributions suggest that at a minimum, single-cell and two-cell vortices are possible at this VorTECH aspect ratio. The pressure distributions and power spectrum plots revealed that the pressure data is concentrated at low a frequency (< 25 Hz) and does not vary with time-scans exceeding five seconds. Preliminary flow visualization studies were undertaken using fog generation, helium-filled bubbles and small particles, however, significant future work remains to be done in this area. VorTECH was successfully completed and is available for use in future studies at Texas Tech University. Due to the uniqueness of its size and design, it holds great potential to enable engineers to better understand the wind-loading effects of tornados on low-rise structures.