Sensitivity Analysis of a Three-Dimensional Wind Tunnel Design

Abstract

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.

Steady headwind display with conditional angular rate-switching control

“…To create a highly immersive system for the user, a haptic interface is essential [1]. In [2,3], the Treadport Active Wind Tunnel (TPAWT) was developed to augment the original Treadport [4] with a wind based haptic interface. Sidewalls, display screens, floor, and ceiling are used to guide airflow supplied through controllable side-vents, Fig 2, to create a pair of counter rotating vortices.…”

“…This allows the user to sense air coming towards them as though it is originating from the scenery displayed on the screens. [3] focused on open loop characterization of the flow whereas [2] provided feedback control of wind speed. In contrast to our previous work [2], wind speed control is now feed-forward since we are focusing on wind angle in this research.…”

“…The return plenum with negative pressure, Fig. 2, was added to the system in [2,3] to stabilize the unsteady wind flow at the user as described in Section V.A. It is a form of predetermined open loop control [5].…”

Combined wind speed and angle control in a virtual environment using a static observer

“…At ratios far from 1, the vortices shift the core flow considerably and the core flow is again attracted to one of the stable equilibrium at θ =± 60 o [2] Hence we consider only the vent velocity ratios in the range from 0.75 to 1.25. A series of simulations were conducted to sweep this range.…”

“…The Treadport Virtual Environment [1] already has a locomotion interface, which allows the user to walk through the virtual environment while viewing realistic rendering on a 180 o CAVE-like display provided by visual screens on the front and the sides. Current works [2][3][4] on augmenting the haptic interface to the original Treadport Virtual Environment [1], termed TreadPort Active Wind Tunnel (TPAWT) involve creating wind flow at the user. A haptic interface improves the sense of immersion for the user [5].…”