Document
Partially-Dressed Cavity-Closed Nose
Landing Gear (PDCC-NLG) Problem
Experiment Description and Results
Dan Neuhart Flow Physics and Control Branch Mehdi Khorrami and Meelan Choudhari Computational Aerosciences Branch NASA Langley Research Center Hampton, Virginia Workshop on Benchmark problems for Airframe Noise Computations (BANC) – I, June 10-11, 2010
This talk describes the nose landing gear
experiments in BART
Model
Background
Experiments
Data Facility
The experimental model was derived from a high-
fidelity model of the Gulfstream G550 aircraft NLG
! High-Fidelity, 25% Scale ! Cavity, Lower Fuselage Section ! 16 Dynamic Pressure Transducers (1 Roving/Mobile) ! 120+ Static Pressure Ports ! PDCC => remove…..
" Hydraulic Lines " Steering Mechanism " Light Cluster " Seal Gear Cavity " All Above # Partially dressed model (simplified gear) Baseline open geometry configuration for benchmarking aeroacoustic simulations
The model component details
Removal of select components produces the PDCC-NLG
configuration
The Basic Aerodynamics Research Tunnel (BART) is
where the NLG was tested
BART Specifications Test section: 0.711m x 1.016m x 3.028m Test Conditions Velocity: 56.6 m/s Re/m: 3.832 x 10 (Re = 73,000) D Mach No: 0.166 Turbulence Intensity: 0.077% * !"#" 0.61” (1.55 cm), ! = 0.086” (0.22 cm)
The experimental data in the problem statement consists
of steady and unsteady surface pressure and PIV
Port wheel – Steady surface pressures - two radial rows Starboard wheel – Door – five spanwise rows one circumferential row Fuselage – one streamwise and two spanwise rows Fluctuating surface pressures - P and PSD – all ten fixed sensors rms (mobile sensor at various gear locations can be made available) p’ time history - one on port wheel one on torque arm two on door Planar PIV data – multiple planes around the model The estimated experimental uncertainties are…….
! Steady Cp ~ 0.02
*
! PIV : Umean,Vmean ~ 1.4 m/s (2.5 % of U )
inf
! PIV: Vorticity ~ 729/s
! PIV: TKE ~ 4%
! PSD ~ 10-14%
! Cp’ ~ 5-7%
rms * the uncertainty in PIV quantities is based on the system velocity resolution, which relates to the minimum displacement (velocity) the system can measure.
The steady Cp on the starboard wheel was invariant with
rotation angle (M=0.166)
Steady pressure orifices spaced 20 deg uncertainty
The steady Cp on the door showed mild variation
spanwise
uncertainty Y (in)
The removal of gear components shows the increase in
coefficient of RMS Unsteady Pressure
(13) (7) (15) (3,4) (12) (10) (8) (5)
The effect of component removal on PSD is significant for
areas of the model in the vicinity of the removed parts
Upper sensor on door Lower sensor on door Upper sensor on drag brace Sensor on back wall of wheel hub
The PIV laser light sheets are shown relative to the model
Starboard_wheel_X-Y_plane1, Z= 16.228 inches Wheel_wake_X-Y_plane1, Z= 17.228 inches Wheel…_plane2, Z= 16.228 inches Wheel…_plane3, Z= 15.228 inches Starboard…_plane2, Z= 15.228 inches Wheel…_plane4, Z= 14.228 inches Wheel…_plane5, Z= 13.228 inches Starboard…_plane3, Z= 14.228 inches Torque-arm_wake, Z= 10.79 inches Door_wake_X-Y_plane1, Z= 9.1 inches Door…_plane2, Z= 7.44 inches Door…_plane3, Z= 6.44 inches Tunnel floor, Z= 0.0 inches
The details of the 2-D PIV system are………
! Lightsheet thickness – 2 mm
! Dual, 220 mJ, Nd-YAG lasers
! Digital camera frame rate – 5 Hz
! Sensor size – 1360X1036 pixels
! Measurement volume –
- 1.3 mm (50 mm lens, 24X24 interrogation window)
(0.0175D)
! 50% interrogation window overlap
! Flow seeded by commercial fog generator
! 1000 image pairs per configuration
The TKE in plane 2 (behind door) shows the concentration
of energy in the shear layers trailing downstream
Port Starboard
Plane 2 (behind door) shows the flow of out-of-plane
vorticity around edges trailing downstream
The instantaneous vorticity and PSD give no evidence of
persistent, coherent structure shed downstream of door
PSD on Starboard Door Edge PORT STARBOARD
The TKE in X-Y PIV plane (Mid-wheel, Starboard Side)
shows concentration of energy in aft wheel hub area
Final Comments – 1 of 2
! Surface pressure spectra were found to be primarily broadband in character and devoid of any local peaks associated with Strouhal shedding ! Removal of select components resulted in stronger pressure fluctuations in certain surface locations ! PIV revealed no large-scale vortical structures shed from gear components corroborating unsteady pressure measurements ! The highest levels of TKE and Cp’ for the PDCC were measured in the rms area of the wheel hub, torque arm, door, and the drag brace
Final Comments - concluded
$ simplified geometry, complicated physics $ ease/difficulty of performing the tests • Instrumentation – in-situ calibration • Model changes " Clocking wheels " Removing components " Moving mobile transducer • Data acquisition and processing $ what (if anything) would make the dataset better $ Comments solicited during open discussion
Background material
The details of the data acquisition are…………
! Signal gain incorporated into sensitivity coefficients through in-situ calibration ! AC-coupled data ! Sample rate: 51.2 kHz ! Blocksize: 16384 ! Number of blocks acquired: 100 ! Anti-alias filter in front of A/D: 20 kHz, elliptic ! AC coupling frequency: 1 Hz ! Range: set as needed for each channel ! DC-coupled data ! Sample rate: 50 Hz ! Number of samples acquired: 1600 ! DC coupling frequency: 1 Hz
References
! Neuhart, D.H., Khorrami, M.R., and Choudhar i, M.M., “Aerodynamics of a Gulfstream G550 Nose Land ing Gear Model,” AIAA Paper 2009-3152, Miami, May 11-13, 2009.
! Neuhart, D. H., Jenkins, L. N., Choudhari, M. M., Khorrami, M. R. , “Measurements of the Flowfield Interaction Between Tandem Cylinders,” AIAA Paper 2009-3152, Miami, May 11-13, 2009.
! Jenkins, L. N., Neuhart, D. H., McGinley, C. B., Khorrami, M. R. , and Choudhari, M. M., “Measurements Of Unsteady Wake Interference Between Tandem Cylinders”, AIAA-2006-3202 (2006).
! Lockard, D. P., Choudhari, D. P., Khorami, M. R., Neuhart, D. H., M. M., Hutcheson, F. V., and Brooks, T. F.,”Aeroacoustic Simulations of Tandem Cylinders with Subcritical Spacing,” AIAA-2008-2862 (2008).
! Coleman, H.W., and Steele, W.G., Experimentation and Uncertainty Analysis for Engineers , John Wiley & Sons, 1999.
! Bendat, J.S. and Piersol, A.G., Random Data , John Wiley & Sons, 2000 ! Raffel, M.,Willert, C., Wereley, S., and Kompenhaus, J., Particle Image Velocimetry , Springer, 2007.