The present paper describes the design of the TreadPort Adaptive Wind Tunnel (TPAWT), which is a wind tunnel retrofit to the University of Utah Treadport Virtual Environment (VE). The TPAWT integrates haptic wind sensation with the preexisting VE, which includes a large tilting treadmill and a cave-like frontal visual display. Desired flow patterns at the center of the TPAWT (where the VE user stands) are generated by appropriately steering the inlet airstream from two sets of vents embedded in the side walls of the facility. Hypothetically, the addition of haptic wind sensation in the virtual environment will improve the sense of immersion in the virtual reality. The present study focuses on quantifying the sensitivity of the flow field inside the TPAWT to perturbations in boundary conditions at the vents. Results from three-dimensional and two-dimensional numerical simulations are compared to laboratory experiments in a 1:4 scale model of the TPAWT. The stability of the flow near the VE user is shown to be highly sensitive to the angle of the mean flow at the vent boundary.
Abstract-This research creates a steady headwind at a user position in the scaled Treadport Active Wind Tunnel (TPAWT). The TPAWT adds a wind display system to the previously developed Treadport virtual environment, and this research builds upon prior work to provide improved control of headwind angle at the user position. Key to this research is the addition of a negative pressure plenum at the rear of the treadport to improve nominal flow stability. The previous controller based upon the small gain theorem with a dynamic extension is then modified to provide wind angle feedback control. A conditional angular rate-switching controller is added to reduce wind angle oscillations at the user. A vorticity-meter is developed to assure that the wind flow is centered at the user position. As a result, this research reduces wind angle error by 75% compared to previous work.
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