WIND TUNNEL INVESTIGATIONS OF TRANSONIC TEST SECTIONS. PHASE I. TESTS OF A 22.5-PERCENT OPEN-AREA PERFORATED-WALL TEST SECTION IN CONJUNCTION WITH A SONIC NOZZLE
ARNOLD ENGINEERING DEVELOPMENT CENTER ARNOLD AFB TN
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The results presented are for a test section with four 22.5-percent open-area perforated walls in conjunction with a sonic nozzle. The major portion of the results presented are for walls with 14-in. diameter perforations in a 116-in. plate. Comparisons are made with results from tests with 116-in. diameter perforations. Variations in wall angle, diffuser flap position, tunnel pressure ratio,hole size and initial expansion region were made to determine the effect on tunnel performance with and without auxiliary suction for a Mach number range of 0.8 to 1.2. Blockage models of 1, 3, and 5 percent were installed to determine blockage effects on suction requirements. Boundary layer profiles were measured along the test section wall with and without the blockage models installed. Taper strips improved the Mach number distributions considerably both in the supersonic and subsonic speed range. With parallel walls and empty test section, a maximum Mach number of 1.125 was obtained with diffuser suction and a maximum tunnel pressure ratio of 1.4. Mach number 1.0 was attained with a tunnel pressure ratio of 1.25. With parallel walls and diffuser flaps closed, the minimum auxiliary suction requirement to attain Mach number 1.0 was 2.2 percent of the main flow. A 5 percent blockage body increased the auxiliary suction to 3.65 percent. With parallel walls and closed diffuser flaps, increasing the hole size from 116 to 14 in. reduced the minimum auxiliary suction from 3.65 to 2.2 percent of the main flow to attain Mach number 1.0. The optimum operating condition for the tunnel at any wall angle is with auxiliary suction and the diffuser flaps completely closed.
- Test Facilities, Equipment and Methods