Structural Acoustics Branch at NASA Langley Research Center

Transcription

1 National Aeronautics and Space Administration Structural Acoustics Branch at NASA Langley Research Center Kevin P. Shepherd Head Richard J. Silcox Asst. Head Overview by Noah H. Schiller 2010 CAV Workshop, Penn State

2 Where we fit Science Space Operations Aeronautics Exploration Overview 2 of 22

3 Where we fit Airspace Systems Science Aeronautics Space Operations Exploration Integrated Systems Research Aviation Safety Fundamental Aeronautics Aeronautics Test Environmentally Responsible Aviation Subsonic Fixed Wing Subsonic Rotary Wing Hypersonics Supersonics Overview 3 of 22

4 What we do Structural Acoustics Human Response Interior Noise Transmission Modeling Measurement Methods Active/passive Control Sonic Fatigue Response Modeling Qual Testing Fatigue Mitigation Psychoacoustics Sonic Boom, Flyover Noise, Interior Noise Simulation & Assessment Noise Impact Modeling Sound Propagation Noise Metrics Engine Nacelle Acoustics Material Characterization Acoustic Design Normal/Flow Impedance Flow resistivity Propagation constant Duct propagation/radiation Liner design Nacelle design Overview 4 of 22

5 Facilities Overview 5 of 22

6 Structural Acoustic Test Facilities Anechoic Room: TL Testing of Aircraft panel Thermal Acoustic Fatigue Apparatus Reverberant Room: Qualification Testing of X-37 Article Overview 6 of 22

7 Human Response Test Facilities Sonic Boom Simulator Interior Effects Room Exterior Effects Room Overview 7 of 22

8 Acoustic Liner Technology Facility Grazing Flow Impedance Tube Curved Duct Test Rig Raylometer Normal Incidence Tube (NIT) Overview 8 of 22

9 Recent Activities Overview 9 of 22

10 Quiet Honeycomb Panels Recessed Core Panel Voided Core Panel Solid Core Panel Overview 10 of 22

11 Structural Concepts: Polyimide Foam Collaboration between NASA, PolyuMAC, Purdue, Gulfstream, Boeing relate acoustic performance to physics-based empirical model couple chemistry/fabrication process with desired acoustic performance Advantages of Polyimide foam: formed at room temperature, cured using microwave energy low density: 0.2 to 1.0 pcf reduced flammability relative to fiberglass insulation Overview 11 of 22

12 Gulfstream/Boeing/NASA Flight Test Objective: Accurate characterization of TBL for structural-acoustic modeling Approach: Heavily instrument a large window blank in a Gulfstream GV Instrumented Window 62 flush-mounted sensors 28 surface-mount sensors Exterior View Interior View Improved Model Overview 12 of 22

13 Sonic Boom Testing - Simulation & Flight NASA Langley Gulfstream NASA Dryden Lockheed-Martin Overview 13 of 22

14 Quiet rotorcraft cabins Overview 14 of 22

15 Technical Challenge: Quiet Cabin Goal: Cabin noise 77 dba SPL with no additional weight penalty Powertrain noise is important high frequency tones Approach: reduce source noise improve modeling tools develop novel structural concepts Overview 15 of 22

16 High Frequency Vibroacoustic Modeling Goal: Get noise into vehicle design support beams, trans. housing: long wavelength Statistical Energy Analysis (SEA) is preferred expertise required separate model must be generated Energy finite elements (EFE) are alternative analyzes coarse finite element model automates structure partitioning acoustic space, sidewall panels: short wavelength Overview 16 of 22

17 Test Structure: Composite Cylinder Overview 17 of 22

18 Automated Impulse Response Decay Method Measured FRFs* 1/3-octave response Impulse responses filter* FFT -1 Schroeder decays regression: fit with single exponential Fit initial [-2,-17] db of decay Results loss factor: goodness of fit metric: R 2 (0<R 2 <1) *Important details: Jacobsen and Bao, JSV, 115(3): , Overview 18 of 22

19 Vibroacoustic modeling v 2 prediction in 2 khz 1/3-octave band using default power transmission coefficients Horizontal variation of v 2 at 2 khz drive point due to errors in pwr. trans. coeffs due to model errors Overview 19 of 22

20 Estimate damping and statistics Overview 20 of 22

21 Propagate damping uncertainty through model Overview 21 of 22

22 Concluding remark Structural Acoustics Branch conducts research to understand and control noise and its effects on aircraft, passengers, crew, and the community Overview 22 of 22

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