Tri-Sonic Wind Tunnel Facility:

It was the late Dr. Seiner's vision to incorporate production level research faciliites into a research education environment that led to the development of the NCPA's Tri-Sonic Wind Tunnel (TSWT) facility.  First operated in 2006, the TSWT can be configured for sub-sonic, tran-sonic, or super-sonic research.  The types of programs for which the wind tunnel has been used include supersonic cavity flow, supersonic store separation, fluid-structure interactions, aero-optics, supersonic mixing, and combustion research.

Air is supplied to the TSWT from a high-volume centrifugal compressor system, which charges two 3000 ft3 supply tanks to a maximum pressure of 600 psi.  The supply tanks incorporate a thermal mass to aid in stabilizing the temperature drop during a test run. The blowdown facility uses a fast-acting sleeve valve operated through closed-loop control to maintain the test section total pressure at a desired set point. With typical run times on the order of 15 to 30 seconds, it is possible to perform 5 to 10 test runs per hour on a continuous basis within thermal limits. As a result, overall testing time is typically dictated by model changes rather than by supply charging. Typical Mach number variations during data collection are less than 0.5%.

Optical Access:

A key feature of the TSWT is the optical access for non-intrusive flow measurements.  A 24'' long, windowed test section can be attached to the 12'' by 12'' nozzle exit.  The extension can be configured with optical grade windows on 3 sides for visual access to either sting or wall mounted models, and the top and bottom wall can be diverged up to 0.25 inches.  The side windows have a view port of 15'' long by 11'' tall, offset so that either the top or the bottom of the test section is flush with the window edge. A 12'' long by 7'' wide view port can be installed in either the top or bottom of the test section as needed.  The remaining, non-windowed wall of the test section extension is typically used for wall mounted models, such as partial fuselage models (constructed by the SLA rapid prototyping method) with payload bays.  This type of model also enables the study of free dropped models.

Subsonic and Transonic Operation:

The subsonic configuration of the wind tunnel utilizes a convergent nozzle with downstream choke flaps to allow tuning of the Reynolds number and Mach number as desired.  For high subsonic or transonic operation, a plenum may be installed at the nozzle exit so that wall boundary layer and shock reflection may be adjusted by suction through slotted walls.  This plenum section contains 5 round porthole windows (0.2 m clear aperture) to allow viewing and measurement from a wide range of angles.  A Mach 1.5 nozzle can be used with the transonic plenum or the test section extension.

Model Support System:

The last main element of the tunnel system is a model support with +/- 3 inches vertical positioning and +/- 20 degree pitch capability.  The pitch and elevation are independent actuators and may be coordinated through software to hold a sting mounted model on tunnel centerline as the pitch angle is varied.

Supersonic Operation:

For supersonic flow above Mach 1.5, a second nozzle assembly is available.  This nozzle box accepts interchangeable nozzle blocks with the current set including designs for Machs 2, 3.5, and 5.  This nozzle box contains conventional round windows (12'' clear aperture) located in the Mach rhombus where the best flow quality is expected.  The test section extension may also be attached at the exit of this nozzle box.