How to Accurately Measure Low Sonic Boom or Model Surface Pressure in Supersonic Wind Tunnels

Morgenstern, John M.

doi:10.2514/6.2012-3215

Cited by 24 publications

(13 citation statements)

References 4 publications

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“…Examining the pointwise mean and standard deviation of these signatures highlights the portions of the signature with a large variation and portions with a small variation. A similar technique is used in wind tunnel testing, where signatures measured at different locations in a wind tunnel test section are spatially averaged to reduce the impact of disturbances in the tunnel [17,18].…”

Section: A Signal Ensemble Mean and Standard Deviationmentioning

confidence: 99%

Nearfield Summary and Statistical Analysis of the Second AIAA Sonic Boom Prediction Workshop

Park

Nemec

2019

Journal of Aircraft

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A summary is provided for the Second AIAA Sonic Boom Workshop held 8-9 January 2017 in conjunction with AIAA SciTech 2017. The workshop used three required models of increasing complexity: an axisymmetric body, a wing body, and a complete configuration with flow-through nacelle. An optional complete configuration with propulsion boundary conditions is also provided. These models are designed with similar nearfield signatures to isolate geometry and shock/expansion interaction effects. Eleven international participant groups submitted nearfield signatures with forces, pitching moment, and iterative convergence norms. Statistics and grid convergence of these nearfield signatures are presented. These submissions are propagated to the ground, and noise levels are computed. This allows the grid convergence and the statistical distribution of a noise level to be computed. While progress is documented since the first workshop, improvement to the analysis methods for a possible subsequent workshop are provided. The complete configuration with flow-through nacelle showed the most dramatic improvement between the two workshops. The current workshop cases are more relevant to vehicles with lower loudness and have the potential for lower annoyance than the first workshop cases. The models for this workshop with quieter ground noise levels than the first workshop exposed weaknesses in analysis, particularly in convective discretization. * Research Scientist, Computational AeroSciences Branch, Mike.Park@NASA.gov, AIAA Senior Member. † Aerospace Engineer, Computational Aerosciences Branch, Marian.Nemec@NASA.gov, AIAA Senior Member.

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Section: A Signal Ensemble Mean and Standard Deviationmentioning

confidence: 99%

Nearfield Summary and Statistical Analysis of the Second AIAA Sonic Boom Prediction Workshop

Park

Nemec

2019

Journal of Aircraft

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“…However, wind tunnels have varying degrees of flow nonuniformities (spatial and temporal fluctuations in Mach number, static pressure, and humidity) [53][54][55] and the models are subject to aeroelastic effects since they are slender and have thin wing sections. This vibration can cause a 10-20% variation in normal force, which is used to infer angle of attack.…”

Section: Test Cases and Resultsmentioning

confidence: 99%

Summary of the 2008 NASA Fundamental Aeronautics Program Sonic Boom Prediction Workshop

Park

Aftosmis

Campbell

et al. 2014

Journal of Aircraft

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The Supersonics Project of the NASA Fundamental Aeronautics Program organized an internal sonic boom workshop to evaluate near-and mid-field sonic boom prediction capability at the Fundamental Aeronautics Annual Meeting in Atlanta, Georgia on October 8, 2008. Workshop participants computed sonic boom signatures for three non-lifting bodies and two lifting configurations. A cone-cylinder, parabolic, and quartic bodies of revolution comprised the non-lifting cases. The lifting configurations were a simple 69-degree delta wing body and a complete low-boom transport configuration designed during the High Speed Research Project in the 1990s with wing, body, tail, nacelle, and boundary layer diverter components. The AIRPLANE, Cart3D, FUN3D, and USM3D flow solvers were employed with the ANET signature propagation tool, output-based adaptation, and a priori adaptation based on freestream Mach number and angle of attack. Results were presented orally at the workshop. This article documents the workshop, results, and provides context on previously available and recently developed methods.

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“…• Spatially average the data over limited model movements in the X or Z direction • Operate the 9x7 tunnel at a higher total pressure (2300 psf) than in previous sonic boom tests • Reduce the freestream humidity to less than 250 ppm and maintain within 4 ppm • Position the model upstream of the leading edge shocks from the rails • Optimize the sampling duration of the reference and data runs The spatial averaging technique was developed to reduce the effect of tunnel flow field spatial distortions on the data at single model positions during supersonic wind tunnel testing. 2,3,30 In sonic boom testing in the 9x7 wind tunnel, the non-uniform flow field causes pressure signatures on the rail to be different for different model positions in the test section. To enable the spatial averaging technique, the model is typically translated a short distance longitudinally (X direction) or vertically (Z direction, away from the rail), and a number of sonic boom signatures are acquired at multiple positions as shown in the waterfall plot in Fig.…”

Section: Test Technique Improvementsmentioning

confidence: 99%

“…However, further testing with rails showed that spatially averaging a series of pressure signatures from a number of model positions significantly improved measurement accuracy. 3 Small ambient pressure oscillations and disturbances caused by small shocks emanating from the tunnel structure are nearly eliminated by spatial averaging techniques.…”

Section: Introductionmentioning

confidence: 99%

Experimental and Computational Sonic Boom Assessment of Boeing N+2 Low Boom Models

Durston

Elmiligui

Cliff

et al. 2014

32nd AIAA Applied Aerodynamics Conference

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Near-field pressure signatures were measured and computational predictions made for several sonic boom models representing Boeing's Quiet Experimental Validation Concept (QEVC) supersonic transport, as well as for three axisymmetric calibration models. The concept was designed under a NASA Research Announcement (NRA) contract to address environmental and performance goals, specifically for low sonic boom loudness levels and high cruise efficiency, for an aircraft anticipated to enter service in the 2020-timeframe. Wind tunnel tests were conducted on the aircraft and calibration models during Phases I and II of the NRA contract from 2011 to 2013 in the NASA Ames 9-by 7-Foot and NASA Glenn 8-by 6-Foot Supersonic Wind Tunnels. Sonic boom pressure signatures were acquired primarily at Mach 1.6 and 1.8, and force and moment data were acquired from Mach 0.8 to 1.8. The sonic boom test data were obtained using a 2-in. flat-top pressure rail and a 14-in. tapered "reflection factor 1" (RF1) pressure rail. Both rails capture an entire pressure signature in one data point, and successive signatures at varying positions along or above the rail were used to improve data quality through spatial averaging. The sonic boom data obtained by the rails were validated with high-fidelity numerical simulations of offbody pressures. The test results showed good agreement between the computational and experimental data when a variety of testing techniques including spatial averaging of a series of pressure signatures were employed. The two wind tunnels generally produced comparable data. NomenclatureCAD = computer-aided design CoR = center of rotation h, h_nose = model altitude at model nose, in. h/L, h_nose_L = model altitude non-dimensionalized by model length HumidAvg = average humidity from wind tunnel sensors, ppm by weight L = model reference length, in. M = Mach number

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How to Accurately Measure Low Sonic Boom or Model Surface Pressure in Supersonic Wind Tunnels

Cited by 24 publications

References 4 publications

Nearfield Summary and Statistical Analysis of the Second AIAA Sonic Boom Prediction Workshop

Nearfield Summary and Statistical Analysis of the Second AIAA Sonic Boom Prediction Workshop

Summary of the 2008 NASA Fundamental Aeronautics Program Sonic Boom Prediction Workshop

Experimental and Computational Sonic Boom Assessment of Boeing N+2 Low Boom Models

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