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Precision high-frequency pressure measurements in ground and flight test


OBJECTIVE: Enable precision measurement of high-frequency acoustic waves in ground and flight test experiment. DESCRIPTION: Advancements in the fields of high-fidelity, massively parallel computing and laser-based diagnostics have provided revolutionary new capabilities enabling detailed insight into the dynamic microscale phenomena that drive the macroscopic behavior of high-speed flows. A notable achievement in this area is the advancement of boundary layer transition estimation methods that provide increasingly accurate estimations of the growth of flowfield instabilities that drive the transition process. Although sophisticated diagnostic methods are capable of detecting and measuring the growth of instabilities that drive transition, assessment and validation of transition estimation methods applied to complex ground test configurations and in flight research requires the efficient, precise, simultaneous measurement of high-frequency pressure fluctuations at a relatively large number of locations on the surface of the test body. This topic seeks to develop innovative new pressure measurement methods capable of measuring high frequency acoustic disturbances within a high-speed boundary layer, yet economically and efficiently utilized in complex ground and flight research configurations. An idealized version of such an instrument would be capable of resolving fluctuation amplitudes on the order of 0.01psia or smaller (0.002psia) and instability frequencies up to 1MHz while operating at temperatures up to 1250 deg. F. The sensor should be capable of maintaining calibration throughout the duration of a ground test campaign and yield quantitative amplitude measurements with uncertainties of 0.5% or less (0.1%). The instrument should be deployable in a manner comparable to conventional pressure measurement transducers and not require special handling during installation. The surface area of the sensor should be less than 2mm in diameter. Finally, the cost per unit if full commercial production is achieved should be less than $2000 per sensor or measurement location. It is understood that successful responses to this topic will not be able to meet the entire list of desirable attributes listed above, but responses are encouraged to attempt to meet as many of the attributes as possible while providing a compelling justification for essential trade-offs in the proposal. Current measurements of the second-mode wave instability are being made as described in references below. This topic seeks innovative improvements in the calibration, sensitivity and size of this current capability. PHASE I: Demonstrate a proof-of-concept version of the instrument within a supersonic boundary layer. Meet proposed frequency and sensitivity objectives. PHASE II: Measure high-frequency acoustic waves within a hypersonic flowfield Mach>6 with a boundary layer edge Mach number greater than 4. Meet proposed objectives for sensitivity, sensor size and operating temperature. PHASE III: Fully demonstrate the entire diagnostic system within an Air Force sponsored ground or flight research campaign at Mach numbers greater than 8. REFERENCES: 1. Shann Rufer, Dennis Berridge,"Experimental Study of Second-Mode Instabilities on a 7-Degree Cone at Mach 6", Paper AIAA-2011-3877, June, 2011. 2. Dennis Berridge, Katya Casper, Shann Rufer, Christopher Alba, Daniel Lewis, Steven Beresh, Steven Schneider."Measurements and Computations of Second-Mode Instability Waves in Several Hypersonic Wind Tunnels,"AIAA-2010-5002, June, 2010. 3. Katya M. Casper, Steven J. Beresh, and Steven P. Schneider. Pressure fluctuations beneath turbulent spots and instability wave packets in a hypersonic boundary layer. Paper 2011-0372, AIAA, January 2011. 4. Katya M. Casper, Steven J. Beresh, and Steven P. Schneider. Spanwise growth of the turbulent spot pressure fluctuation field in a hypersonic boundary layer. Paper 2011- 3873, AIAA, June 2011. 5. Kimmel, R. L., Adamczak, D., and Brisbane DSTO-AVD Team,"HIFiRE-1 Preliminary Aerothermodynamic Experiments,"AIAA paper 2011-3414, June 2011. 6. Hofferth JW, Saric WS. Boundary-layer Transition on a Flared Cone in the Texas A & M Mach 6 Quiet Tunnel. AIAA Paper 2012-0923.
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