Boundary-Layer Transition Measurements in the Boeing/AFOSR Mach-6 Quiet Tunnel

Abstract

Recent results from several projects in the BAM6QT are presented. An infrared camera system was used to image a circular cone at an angle of attack, and the results are compared to previous TSP measurements. The IR images show clear streaks and demonstrate repeatability and low noise levels compared to TSP. Oil flow and surface pressure sensor measurements are presented for a cone with a slice and ramp. Separation and reattachment are discussed, along with the amplification and dampening of instabilities at various locations on the model. The temperature distribution along the BAM6QT nozzle wall was varied to study the relationship between heating and the percentage of a run which was quiet. No apparent correlation was observed. Pitot-probe measurements were taken at various locations on the nozzle centerline to investigate an increase in noise levels that occurs roughly two seconds into runs. The magnitude of the increase and the time at which it started depended on the Reynolds number. Development of higher-Reynolds number hypersonic quiet tunnel facilities may require the use of suction on the nozzle wall. Initial computations are presented for the design of a flared inlet centerbody that can be tested in the Boeing AFOSR/Mach-6 Quiet tunnel to determine the feasibility of creating sufficiently uniform suction. A stability analysis is performed to determine the most unstable second-mode frequencies and to compute the Görtler numbers on the flared aft-body portion. Finally, the 3 inch shock tube used for PCB calibration has been upgraded with high accuracy sensors and an automated pressure control system.

Measurements in the Boeing/AFOSR Mach-6 Quiet Tunnel on Hypersonic Boundary-Layer Transition

“…A more thorough examination of repeatability for the Modular Cone is provided in previous work. 36,44 Figure 17 shows the repeatability data from the present experiment. In Figure 17 PCBs are about 0.5 • wider than at the downstream location.…”

“…Preliminary IR data has been discussed previously. 44 The PEEK insert can accommodate 24 PCB132 high-frequency pressure sensors and 9 Kulite XCQ-062 transducers. There are 19 PCBs along a single ray, starting at x = 265.5 mm and spaced every 6.3 mm.…”

“…Initial experiments have been completed over the past year. 36,44 However, this model did not have a ramp long enough to allow for measurements of the boundary layer post-reattachment. Since post-reattachment measurements are needed for determining the effect of the free shear layer on transition, a new model was designed.…”

Measurements of Freestream Fluctuations in the NASA Langley 20-Inch Mach 6 Tunnel

“…14 Attempts to calibrate the sensors in a shock tube have been ongoing at Purdue University. 15,16 No method of dynamic calibration was applied to the sensors shown in this paper, so the factory calibration was used. The PCB sensors were flush-mounted in a 6.35-mm-diameter stainless steel body that had a 3-degree taper on the front end of the probe.…”

“…24. The fast Fourier transform (FFT) of this quantity is computed using Welch's method with a 2 16 -point (0.0066 s) Hanning window with 50% overlap. This yields a frequency spacing of 152.6 Hz to be consistent with the other power spectra.…”