Step-Temperature Effects on Direct Measurements of Drag

Westkaemper, J. C.

doi:10.2514/3.1907

Cited by 9 publications

(2 citation statements)

References 2 publications

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“…Westkaemper examined the effects of temperature mismatch on direct measurements of drag at Mach 5 and mismatch temperature ratios from 0.92 to 1.09 on a flat plate. 21 He found that "there was no apparent correlation of the drag variation with the conditions of temperature mismatch." The drag variation found in Westkaemper's experiment was within the repeatability of ±2 percent of his measurements; therefore, "the variation in drag did not appear to be related to the mismatch condition, but appeared rather to be random in nature."…”

Section: Flight Test Resultsmentioning

confidence: 99%

In-Flight Capability for Evaluating Skin-Friction Gages and Other Near-Wall Flow Sensors

Bui

Pipitone

Krake

2003

41st Aerospace Sciences Meeting and Exhibit

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An 8-in.-square boundary-layer sensor panel has been developed for in-flight evaluation of skin-friction gages and other near-wall flow sensors on the NASA Dryden Flight Research Center F-15B/Flight Test Fixture (FTF). Instrumentation on the sensor panel includes a boundary-layer rake, temperature sensors, static pressure taps, and a Preston tube. Space is also available for skin-friction gages or other near-wall flow sensors. Pretest analysis of previous F-15B/FTF flight data has identified flight conditions suitable for evaluating skin-friction gages. At subsonic Mach numbers, the boundary layer over the sensor panel closely approximates the two-dimensional (2D), law-of-the-wall turbulent boundary layer, and skin-friction estimates from the Preston tube and the rake (using the Clauser plot method) can be used to evaluate skin-friction gages. At supersonic Mach numbers, the boundary layer over the sensor panel becomes complex, and other means of measuring skin friction are needed to evaluate the accuracy of new skin-friction gages. Results from the flight test of a new rubber-damped skin-friction gage confirm that at subsonic Mach numbers, nearly 2D, law-of-the-wall turbulent boundary layers exist over the sensor panel. Sensor panel data also show that this new skin-friction gage prototype does not work in flight. Subscripts aw adiabatic wall e edge of boundary layer w w all REPORT DOCUMENTATION PAGE Form Approved OMB No. 0704-0188 Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to

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Section: Flight Test Resultsmentioning

confidence: 99%

In-Flight Capability for Evaluating Skin-Friction Gages and Other Near-Wall Flow Sensors

Bui

Pipitone

Krake

2003

41st Aerospace Sciences Meeting and Exhibit

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“…Westkaemper found little error for the temperature mismatch for small differences, as opposed to the large differences of the Voisinet work. 76 However, when one reinterprets the Westkaemper data in the terms Voisinet used, the two correlate. An extensive computational and experimental study of this problem was undertaken by Debieve, et al 77 The major conclusion is that the error is caused largely through changes in the local thermal properties and not on any in the boundary layer profile.…”

Section: Step-temperature Effectsmentioning

confidence: 99%

Development of fiber optic aerodynamic sensors for high Reynolds number supersonic flows

Pulliam¹,

Schetz²

2001

39th Aerospace Sciences Meeting and Exhibit

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Aerospace Engineering (ABSTRACT)The purpose of the project was to examine fiber optic sensors for the measurement of pressure, skin friction, temperature, and heat flux in high Reynolds number, supersonic flow. Using a standard fiber optic signal conditioning unit (specifically a broadband interferometric system using spectra), the work centered around determining under what conditions these sensors will work effectively and quantifying the total system limitations.An interferometric-based, fiber optic skin friction sensor was developed for the measurement of wall shear stress in complex, supersonic flows. This sensor type was tested successfully in laminar, incompressible flow, and supersonic flow up to Mach 1.92, Mach 2.4 and 3.0 flow, in which the sensor operated with varying success. A micromachined, fiber optic pressure sensor was also tested in these supersonic conditions, also with varying success. The accurate operation of these sensors was found to be tied to the flow conditions and the fiber optic, signal processing system.A correlation was found to exist between the energy of the flow, either through its dynamic pressure or through external disturbances such as shocks or separation, and the noise in the signals, expressed by the variance of the gap estimate, for the pressure and skin friction sensors in these flows. The energy of the flow couples with the mechanical properties of the sensor reducing the fringe contrast of the signal used by the optical signal processing system to determine a gap estimate. As the energy of the flow is increased and the sensor is excited, the fringe contrast is reduced. A practical limit of a normalized fringe contrast of 0.10 was found for producing accurate gap estimates in real flows. A consequence is that there is a limit to the dynamic pressure of the flow for the sensors to operate accurately, which is demonstrated by the varying success of the supersonic wind tunnel tests. This correlation is sensor specific, meaning that sensors can be designed to operate successfully in any flow. Also, the signal processing system, which forms the other end of the total system, could be improved to allow accurate measurements with the current sensors.iii

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An outline of the techniques available for the measurement of skin friction in turbulent boundary layers

Winter¹

1979

Progress in Aerospace Sciences

271

109

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Step-Temperature Effects on Direct Measurements of Drag

Cited by 9 publications

References 2 publications

In-Flight Capability for Evaluating Skin-Friction Gages and Other Near-Wall Flow Sensors

In-Flight Capability for Evaluating Skin-Friction Gages and Other Near-Wall Flow Sensors

Development of fiber optic aerodynamic sensors for high Reynolds number supersonic flows

An outline of the techniques available for the measurement of skin friction in turbulent boundary layers

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