11

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

22

aperture pad locationsaperture pad locations

33

rake & rake & HIMIL HIMIL

locationlocationscheduleschedule

44

aperture pads on G-5aperture pads on G-5

related measurementsrelated measurements

55

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

66

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

77

pressure rake & scannerpressure rake & scanner

∆p = 16 channels

ethernet

50 Hz

88

rake mounted on bellyrake mounted on belly

99

flight test maneuversflight test maneuvers

speeds & altitudesspeeds & altitudes• normal operating rangenormal operating range

1010

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.

1111

dynamic pressure profilesdynamic pressure profiles - different aperture pad locations -- different aperture pad locations -

1212

pitch, side-slip & speed run maneuverspitch, side-slip & speed run maneuvers- rake at belly 250-R -- rake at belly 250-R -

1313

BL depthBL depth

1414

pitch & side-slip maneuverspitch & side-slip maneuvers- rake at belly 250-R -- rake at belly 250-R -

1515

zoom-inzoom-in

1616

profiles during pitch maneuversprofiles during pitch maneuvers

1717

profiles during side-slipprofiles during side-slip

1818

BL DEPTH - measured vs GAC studyBL DEPTH - measured vs GAC study

1919

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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/

2020

speed & AOAspeed & AOA- envelope of flight conditions -- envelope of flight conditions -

color = flight i.d.

dot = 1 sec of flight