Oscillations in a Forward-Facing Cavity Measured Using Laser-Differential Interferometry in a Hypersonic Quiet Tunnel

AFOSR/NA Unclassified and Approved for Public Release M.S. thesis by Rodrigo Segura with development of LDI for Mach-6 quiet tunnel and measurements in Mach-4 quiet tunnel Laminar-turbulent transition is a pivotal factor for the design of hypersonic vehicles but the mechanisms that induce transition are not well understood. A laser differential interferometer (LDI) is a non-intrusive optical device that measures the optical path length difference between two laser beams. The LDI is a reliable calibrated instrument to assist the study of boundary layer instability-wave growth in hypersonic flow and has high sensitivity and frequency response. An LDI with a commercial balanced photodetector capable of detecting optical path length differences of lambda/21,000 from DC to 80 MHz was assembled and tested in the Purdue Quiet-Flow Ludwieg tube. Fluctuations in the subsonic region of a forward-facing cavity were measured with the LDI and compared to those detected with a Kulite pressure transducer at the base of the cavity. Predictions of self-resonating deep cavities were confirmed. The LDI was then adapted and transferred to the Boeing/AFOSR Mach-6 Quiet Tunnel. hypersonic boundary layer transition optical instrument supersonic cavity flow oscillations experiment Unclassified Unclassified Unclassified Unlimited 151 ii Este trabajo va dedicado a mi papá, mi mamá, mi hermano, y mi Dios. A ustedes les debo todo lo que soy. iii ACKNOWLEDGMENTS I want to thank my advisor, Professor Steven P. Schneider for building and managing the hypersonic wind tunnels at Purdue University and giving me the opportunity to work on this project. Had it not been for his vote of confidence, the LDI would sit in a drawer for years to come. Furthermore, his expertise and frankness helped me get through the difficulties encountered in this experimental research. I would also like to thank my committee members, Professors Steven H. Collicott and Anastasios S. Lyrintzis, their guidance and suggestions are appreciated. The machinists and technicians at the Purdue Aerospace Sciences Laboratory were extremely helpful during the course of the project. I thank them for their excellent craftsmanship and valuable technical assistance. I would like to express my special gratitude to Madeline Chadwell, Robin Snodgrass, and John Phillips all of whom went out of their way to assist me with unexpected experimental breakdowns on multiple occasions. Jerry Hahn and Jim Younts were also included in that crew. The office and information systems staff at the Aeronautical and Astronautical Engineering department at Purdue University also played an important role. Linda Flack's timely reminders made the logistics of my academic life easy. I would like to give special thanks to Joan Jackson; she made me laugh and was patient and helpful even when I demanded her help on rather short notice. Joe Kline's technical assistance is appreciated. A great deal of contribution came from my fellow researchers.

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“…See Ref. 34 for further details on the performance of each optical element and the theory behind the LDI.…”

Section: Ldi Developmentmentioning

confidence: 99%

Starting Issues and Forward-Facing Cavity Resonance in a Hypersonic Quiet Tunnel

Juliano

Segura

Borg

et al. 2008

38th Fluid Dynamics Conference and Exhibit

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“…The experimental results perfectly agree with the predicted results of "E3", while results for "L", "E1" and "E2" are larger than experimental results (Figure 9). Ladoon et al [8] and Segura [20] performed experiments on a forward-facing cavity of Q ⁄ 0.5 and / ∈ H0.5, 3.0K . The experimental results equal to the results predicted by "E3" method for most of the conditions ( Figure 12).…”

Section: Oscillation Frequencymentioning

confidence: 99%

Prediction of Shock-Standoff Distance and Entropy Distribution for Forward-Facing Cavity

Wang¹

2018

IJASS

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Experiments are performed on a cylinder with a forward-facing cavity at M ∞ = 10 in the FD-14A shock tunnel. The shock-standoff distance and oscillation characteristics are recorded by a high-speed movie, and the dynamic pressure transducer is used to capture the unsteady signal of cavity base. Based on experimental and numerical results, a prediction method for estimating the shock-standoff distance is proposed. Results of shock-standoff distance and oscillation frequency are obtained for experiments in the shock tunnel. The predicted oscillation frequency is in accordance with experimental results. Furthermore, the relation of shock shape and the entropy increase are combined to obtain the characteristics of entropy distribution. As the shock-shape of flat-nosed cylinders is more liable to be influenced than blunt-nosed cylinders with increasing Mach number, the location of the extreme value moves to the surface as the Mach number increases for flat-nosed cylinders, while it remains the identical location for blunt-nosed cylinders.

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“…17 The maximum depth possible for this model is L/D = 5.00. The depth was varied by sliding the cylindrical steel insert back and forth, and held constant by tightening set screws on the side of the model.…”

Section: B Model and Instrumentationmentioning

confidence: 99%

Boundary-Layer Instability Measurements in a Mach-6 Quiet Tunnel

Berridge

Ward

Luersen

et al. 2012

42nd AIAA Fluid Dynamics Conference and Exhibit

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Several experiments have been performed in the Boeing/AFOSR Mach-6 Quiet Tunnel at Purdue University. A 7• half angle cone at 6• angle of attack with temperature-sensitive paint (TSP) and PCB pressure transducers was tested under quiet flow. The stationary crossflow vortices appear to break down to turbulence near the lee ray for sufficiently high Reynolds numbers. Attempts to use roughness elements to control the spacing of hot streaks on a flared cone in quiet flow did not succeed. Roughness was observed to damp the second-mode waves in areas influenced by the roughness, and wide roughness spacing allowed hot streaks to form between the roughness elements. A forward-facing cavity was used for proof-of-concept studies for a laser perturber. The lowest density at which the freestream laser perturbations could be detected was 1.07 × 10 −2 kg/m 3 . Experiments were conducted to determine the transition characteristics of a streamwise corner flow at hypersonic velocities. Quiet flow resulted in a delayed onset of hot streak spreading. Under low Reynolds number flow hot streak spreading did not occur along the model. A new shock tube has been built at Purdue. The shock tube is designed to create weak shocks suitable for calibrating sensors, particularly PCB-132 sensors. PCB-132 measurements in another shock tube show the shock response and a linear calibration over a moderate pressure range. Nomenclature

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Oscillations in a Forward-Facing Cavity Measured Using Laser-Differential Interferometry in a Hypersonic Quiet Tunnel

Cited by 9 publications

References 28 publications

Starting Issues and Forward-Facing Cavity Resonance in a Hypersonic Quiet Tunnel

Starting Issues and Forward-Facing Cavity Resonance in a Hypersonic Quiet Tunnel

Prediction of Shock-Standoff Distance and Entropy Distribution for Forward-Facing Cavity

Boundary-Layer Instability Measurements in a Mach-6 Quiet Tunnel

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