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Measuring the flow boundary layer on HIAPER's Measuring the flow boundary layer on HIAPER's fuselagefuselage
Rogers, Fox, Lord, Stith, Maclean, EOL technical staff, Friehe, McCluskyRogers, Fox, Lord, Stith, Maclean, EOL technical staff, Friehe, McClusky
goal:goal:
• measure air speed at aperture pad locations where air sample inlets measure air speed at aperture pad locations where air sample inlets and other equipment can be mountedand other equipment can be mounted
motivation: motivation: • inlets must sample air outside the BL to avoid contamination or inlets must sample air outside the BL to avoid contamination or
interactions with aircraft skininteractions with aircraft skin• estimate thickness of flow boundary layerestimate thickness of flow boundary layer• adjust inlet suction rates to optimize air samplingadjust inlet suction rates to optimize air sampling
taskstasks• design & build a pressure rakedesign & build a pressure rake• acquire other hardwareacquire other hardware• develop software to log datadevelop software to log data
Progressive Science:Progressive Science: 13 flights, Dec 1-22, 200513 flights, Dec 1-22, 2005
results:results:
measured profiles of dynamic pressure within 30 cm of the aircraft skin measured profiles of dynamic pressure within 30 cm of the aircraft skin at four aperture padsat four aperture pads
June 2006June 2006
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true air speed ~ (true air speed ~ (ΔΔp)p)1/21/2
Bernoulli’s equation: Bernoulli’s equation: p = pp = p00 + ½ + ½ xx density density xx velocity velocity22
RAF RAF Bulletin No. 23Bulletin No. 23, , Measurement Techniques: Air Motion SensingMeasurement Techniques: Air Motion Sensing, ,
http://www.atd.ucar.edu/raf/Bulletins/bulletin23.htmlhttp://www.atd.ucar.edu/raf/Bulletins/bulletin23.html
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velocity profilevelocity profile
law of the walllaw of the wall
logarithmic velocity profile within inertial logarithmic velocity profile within inertial sublayersublayer
U / uU / u** = (1/ = (1/кк) ln y) ln y++ + const + const
where uwhere u** = friction velocity, y = friction velocity, y++ = scale height = scale height
кк = von Karmen’s constant = von Karmen’s constant
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flight test maneuversflight test maneuvers
speeds & altitudesspeeds & altitudes• normal operating rangenormal operating range
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dynamic pressure profilesdynamic pressure profiles - speed runs -- speed runs -
““boundary layer depth”boundary layer depth”• distance from skin distance from skin
where speed = 99% of where speed = 99% of local asymptotic local asymptotic velocity, (or 98% of velocity, (or 98% of asymptotic dynamic asymptotic dynamic pressure)pressure)
• not necessarily the not necessarily the “freestream” value, “freestream” value, which is further away which is further away from the aircraft. from the aircraft.
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dynamic pressure profilesdynamic pressure profiles - different aperture pad locations -- different aperture pad locations -
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pitch, side-slip & speed run maneuverspitch, side-slip & speed run maneuvers- rake at belly 250-R -- rake at belly 250-R -
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pitch & side-slip maneuverspitch & side-slip maneuvers- rake at belly 250-R -- rake at belly 250-R -
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Univ. California Irvine Univ. California Irvine studies (Friehe, McClusky)studies (Friehe, McClusky)
GAC interest in collaborative study of G-V fuselage BLGAC interest in collaborative study of G-V fuselage BL
• acoustics, cabin noise acoustics, cabin noise
• CFD flow modeling & compare vs rake dataCFD flow modeling & compare vs rake data
ProgSci project web siteProgSci project web site
http://www.atd.ucar.edu/raf/Projects/ProgSci/http://www.atd.ucar.edu/raf/Projects/ProgSci/
more about pressure rakemore about pressure rake
http://www.atd.ucar.edu/~dcrogers/ProgSci/PressureRake/http://www.atd.ucar.edu/~dcrogers/ProgSci/PressureRake/