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Measuring the flow boundary layer on HIAPER's fuselage Rogers, Fox, Lord, Stith, Maclean, EOL technical staff, Friehe, McClusky. goal: measure air speed at aperture pad locations where air sample inlets and other equipment can be mounted motivation:

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  1. Measuring the flow boundary layer on HIAPER's fuselageRogers, Fox, Lord, Stith, Maclean, EOL technical staff, Friehe, McClusky • goal: • measure air speed at aperture pad locations where air sample inlets and other equipment can be mounted • motivation: • inlets must sample air outside the BL to avoid contamination or interactions with aircraft skin • estimate thickness of flow boundary layer • adjust inlet suction rates to optimize air sampling • tasks • design & build a pressure rake • acquire other hardware • develop software to log data • Progressive Science:13 flights, Dec 1-22, 2005 • results: measured profiles of dynamic pressure within 30 cm of the aircraft skin at four aperture pads June 2006

  2. aperture pad locations

  3. rake & HIMIL locationschedule

  4. aperture pads on G-5 related measurements

  5. true air speed ~ (Δp)1/2 • Bernoulli’s equation: p = p0 + ½ x density x velocity2 • RAF Bulletin No. 23, Measurement Techniques: Air Motion Sensing, http://www.atd.ucar.edu/raf/Bulletins/bulletin23.html

  6. velocity profile • law of the wall logarithmic velocity profile within inertial sublayer U / u* = (1/к) ln y+ + const where u* = friction velocity, y+ = scale height к = von Karmen’s constant

  7. pressure rake & scanner ∆p = 16 channels ethernet 50 Hz

  8. rake mounted on belly

  9. flight test maneuvers • speeds & altitudes • normal operating range

  10. dynamic pressure profiles- speed runs - • “boundary layer depth” • distance from skin where speed = 99% of local asymptotic velocity, (or 98% of asymptotic dynamic pressure) • not necessarily the “freestream” value, which is further away from the aircraft.

  11. dynamic pressure profiles- different aperture pad locations -

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

  13. BL depth

  14. pitch & side-slip maneuvers- rake at belly 250-R -

  15. zoom-in

  16. profiles during pitch maneuvers

  17. profiles during side-slip

  18. BL DEPTH - measured vs GAC study

  19. next • Univ. California Irvine studies (Friehe, McClusky) • GAC interest in collaborative study of G-V fuselage BL • acoustics, cabin noise • CFD flow modeling & compare vs rake data • ProgSci project web site • http://www.atd.ucar.edu/raf/Projects/ProgSci/ • more about pressure rake • http://www.atd.ucar.edu/~dcrogers/ProgSci/PressureRake/

  20. speed & AOA- envelope of flight conditions - color = flight i.d. dot = 1 sec of flight

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