Aerodynamic and aerothermal instrumentation - Measurement uncertainty in the NSWC Hypervelocity Wind Tunnel No. 9

Hedlund, Eric; Kammeyer, Mark

doi:10.2514/6.1996-2210

Cited by 8 publications

(1 citation statement)

References 4 publications

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“…The speci c procedures employed in Tunnel 9 are given in Ref. 15. In general, the uncertainty in a measurement was composed of a combination of xed error or bias B, and random error or precision P. The rss model was used to estimate the uncertainties at the 95% con dence level: …”

Section: Measurement Uncertaintymentioning

confidence: 99%

Experimental Results on a Mach 14 Waverider with Blunt Leading Edges

Gillum

Lewis

1997

Journal of Aircraft

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The results of wind-tunnel tests of a Mach 14 waverider were analyzed to assess its overall performance. The waverider was optimized using a gure of merit that included viscosity, volume, and lift-to-drag considerations. The nal design included a 0.25-in. leading-edge radius. The general performance of the tested waverider was analyzed and compared to the theoretical design from which it was derived. The theoretical design was generated from a conical ow eld, where the vehicle's in nitely sharp leading edges were everywhere-attached to the conical shock. Since the tested waverider featured blunt leading edges, it was important to assess the performance losses associated with ow spillage; these losses were found to be relatively small. However, the increased drag due to the blunt leading edges contributed greatly to reducing the aerodynamic performance of the tested waverider. Also, it was found that the aerodynamic coef cient data were insensitive to changes in Mach number and Reynolds number, indicating excellent off-design performance for the ranges of values tested. Nomenclature B= bias error at 95% con dence level C D = drag coef cient C L = lift coef cient C M = pitching-moment coef cient Cw = Chapman -Rubesin parameter, (ru) w/ (ru)L /D = lift-to-drag ratio M`= freestream Mach number P = precision error at 95% con dence level, t 95 S P`= freestream pressure, psia Re = unit Reynolds number S = sample standard deviation t 95 = 95th percentile point for Student's t distribution U rss = uncertainty [B 2 1 P 2 ] 1/2 XCP p = pitch c.p., fraction of model length aft of nosē x = viscous interaction parameter

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Section: Measurement Uncertaintymentioning

confidence: 99%

Experimental Results on a Mach 14 Waverider with Blunt Leading Edges

Gillum

Lewis

1997

Journal of Aircraft

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Uncertainty of Aerodynamic Coefficients at Hypersonic Wind Tunnels

Nagai¹,

Tsuda²,

Koyama³

et al. 2003

JOURNAL OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCE

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In order to estimate the wind tunnel data uncertainty, it is necessary to consider the error propagation caused by the tunnel flow quality. At the NAL 1.27 m hypersonic wind tunnel, multi point calibration tests of the flow field and 6-component force tests of a winged vehicle model were conducted to estimate uncertainties of aerodynamic coefficients. A statistical assessment of Mach number distributions in the uniform core flow gave us an uncertainty of dynamic pressure. Contributions of each uncertainty to the result uncertainties were examined and the large contributions of the dynamic pressure uncertainty were found. These estimated uncertainties were validated by repeat test results and comparisons of the same model test results obtained in another wind tunnel at the same test condition. This uncertainty estimation method is appropriate for hypersonic wind tunnel testing since the model existence gives little effect on the upstream flow.

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