9-by 7-foot Supersonic Wind Tunnel
9-by 7-foot Supersonic Wind Tunnel
• Mach Range = 1.55 to 2.55• Rn = 0.50 to 5.7 million per foot
• Pt = 2.8 to 29.5 psia
• Maximum stagnation temperature: 600°R
• Closed circuit, single return, variable density, continuous flow wind tunnel
• Interchangeability of models between Unitary test sections allows testing across a wide range of conditions
• Internal strain-gage sting mount, model component balances are used for measuring forces and moments. Ames and Langley inventories typically available
• Full support of DTC PSI module capability
• Fully automated control of tunnel conditions and simultaneously variable pitch and yaw positions
• Capability for measuring multiple fluctuating pressures
• There are two controllable 3000 psi auxiliary air systems capable of flow rates up to 40 lb/sec each. One line can be controlled up to 80 degrees F and the other up to 400 degrees F
• Full data system support capability included (Unix system with extra X-terminals available)
• Full internal and external network capability. PCs and Macs available to customers as needed
• Typical two weeks of model build up and instrument preparation is included in the facility occupancy charge
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* Total test section length = 18 ft. Effective (useable) Length = 11 ft. |
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9x7 Supersonic Wind Tunnel Test Section
Dimensions
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A traversing strut downstream of the test section can be programmed to translate horizontally to maintain a desired point of rotation throughout the horizontal-plane angle-range, generally angle-of-attack.
The center of rotation in the vertical plane is 5.3 inches aft of the strut leading edge. The horizontal and vertical plane angles are continuously variable and are determined by the relative positions of a knuckle and sleeve inside the support body. The model support system can position the model at attitudes circumscribed by a 15-degree half-angle cone.
Bent primary adapters of 5, 10, 12.5, and 20 degrees are available to alter the range of model angles.
Numerous stings of differing lengths and taper arrangements are also in inventory.
Forces and moments about the model support center of rotation in the tunnel axis are limited to:
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Vertical |
+ 4,000 lbs |
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Lateral |
+ 8,000 lbs |
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Axial |
+ 3,000 lbs |
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Rolling moment |
+ 104,000 in-lbs |
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Combined vertical and lateral bending moment |
+ 800,000 in-lbs |
Flow visualization techniques such as Schlieren, Pressure Sensitive Paint, Oil Flow, Tufts, Sublimation, Skin Fricion Interferometry, Laser Vapor Screen and Liquid Crystal can be obtained by appropriately positioning 2.35-foot diameter optical quality windows in the test section sidewalls. Still and color video capability are provided.
High-pressure air (3,000 psi) is available at weight flows up to a total of 80 pounds per second through dual, independently controlled digital valves. Air from one of these lines can be preheated using a one megawatt moveable heater.
Shock waves reflecting on the model from the solid test section walls will have a detrimental effect on the model forces and pressures and must be avoided. When determining appropriate model size and attitude, calculate the shock rhombus by assuming reflections at the Mach angle from a 4-inch thick wall boundary layer.
The design of models to be tested in the 9x7ft Supersonic Wind Tunnel must allow for additional critical conditions associated with blockage (the ratio of model-projected frontal area to test section cross-sectional area) and transient starting loads. Large model blockages provide a potential to "unstart" the airflow, allowing a strong shock wave to pass through the test section resulting in possible damage to the model, sting and balance. The ratio of model wing span to tunnel width for minumum supersonic performance verification interference should not significantly exceed 0.5. The maximum recommended ratio of model cross-sectional area to test section cross-sectional area is about 0.010 (model at 0° angle of attack).
Normal procedure is to reduce the tunnel pressure and position the model for minimum loads before beginning the acceleration to, or deceleration from, supersonic conditions.
However, significant transient loads are still generated by the swirling, subsonic, separated flows preceding the establishment of sonic velocity in the upstream throat. To ensure that a model, sting and balance will withstand these transients, they must be designed to withstand the empirically derived starting loads indicated in the following charts.
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9x7 Supersonic Wind Tunnel Load Locations * Click on image to enlarge |
Vertical Primary Lifting Surfaces: Side Force (Vertical Direction) Normal Force(Horizontal Direction) Horizontal Primary Lifting Surfaces: Side Force (Horizontal Direction) Normal Force (Vertical Direction) |
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