1 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 measure air speed at aperture pad locations where air sample inlets and other equipment can be mountedmotivation: inlets must sample air outside the BL to avoid contamination or interactions with aircraft skin inlets must sample air outside the BL to avoid contamination or interactions with aircraft skin estimate thickness of flow boundary layer estimate thickness of flow boundary layer adjust inlet suction rates to optimize air sampling adjust inlet suction rates to optimize air samplingtasks design & build a pressure rake design & build a pressure rake acquire other hardware acquire other hardware develop software to log data 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 location schedule

4 aperture pads on G-5 related measurements

5 true air speed ~ (Δp) 1/2 Bernoulli’s equation: p = p 0 + ½ x density x velocity 2 RAF Bulletin No. 23, Measurement Techniques: Air Motion Sensing,

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 rangenormal 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)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.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 noiseacoustics, cabin noise CFD flow modeling & compare vs rake dataCFD flow modeling & compare vs rake data ProgSci project web site more about pressure rake

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