emeritus professor bob randall - pennsylvania state university · • structural and acoustic...
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Acoustics and vibration research at the University of New South Wales, Australia
Emeritus Professor Bob RandallSchool of Mechanical and Manufacturing Engineering
UNSW AustraliaWith contributions from
Associate Professor Nicole KessissoglouAssociate Professor Con Doolan and Dr Danielle Moreau
Overview of UNSW
• Located in Sydney• Founded in 1949• 45,000 students• 5,000 staff
8 Faculties of UNSW
• Arts and Social Sciences• Australian School of Business• Built Environment• College of Fine Arts• Engineering• Law• Medicine• Science
Faculty of Engineering
9 Engineering Schools• Biomedical Engineering• Chemical Engineering• Civil and Environmental Engineering• Computer Science and Engineering• Electrical Engineering and Telecommunications• Mechanical and Manufacturing Engineering• Mining Engineering• Photovoltaics and Renewable Energy Engineering• Petroleum Engineering
UNSW Engineering RankingsQS World University Rankings by Faculty of Engineering• 27 in 2014• 33 in 2013
Shanghai Jiao Tong World University Rankings by Faculty of Engineering• 42 in 2014• 57 in 2013
School of Mechanical &Manufacturing Engineering5 Bachelor degrees offered within the School of Mechanical and Manufacturing Engineering:• Mechanical• Mechatronic• Manufacturing• Aerospace• Naval Architecture
Personnel• Academic and research staff 40• Laboratory & workshop staff 22• Administrative staff 12• Undergraduate students 1100• Masters by coursework students 140• PhD students 140
Vibration and Acoustics Group
Associate Professor Nicole KessissoglouSchool of Mechanical and Manufacturing Engineering
UNSW Australia
Research Activities
• Structural and acoustic responses of underwater vehicles
• Numerical finite element / boundary element modelling
• Flow induced noise / vorticity induced vibration
• Vibration analysis of structures with uncertainties
• Barrier acoustics
• Porous materials
• Analytical models
Caresta, Kessissoglou, Structural and acoustic responses of a fluid‐loaded cylindrical hull withstructural discontinuities, Applied Acoustics, 70, 954–963 (2009)
Caresta, Kessissoglou, Free vibrational characteristics of isotropic coupled cylindrical‐conical shells, Journal of Sound and Vibration, 329, 733‐751 (2010)
Caresta, Kessissoglou, Vibration of fluid loaded conical shells, Journal of the Acoustical Society of America, 124, 2068–2077 (2008)
Underwater Vehicles
Merz, Kinns, Kessissoglou, Structural and acoustic responses of a submarine hull due to propeller forces, Journal of Sound and Vibration, 325, 266‐286 (2009)
• Analytical / numerical models
Dylejko, Kessissoglou, Tso, Norwood, Optimisation of a resonance changer to minimise the vibration transmission in marine vessels, Journal of Sound and Vibration, 300, 101‐116 (2007)
Merz, Kessissoglou, Kinns, Marburg, Minimisation of the sound power radiated by a submarine through optimisation of its resonance changer, Journal of Sound and Vibration, 329, 980‐993 (2010)
Propeller/Shafting System
Caresta, Kessissoglou, Active control of sound radiated by a submarine hull in axisymmetric vibration using inertial actuators, Journal of Vibration and Acoustics, Transactions of the ASME, 134, 011002 (2012).
Merz, Kessissoglou, Kinns, Marburg, Passive and active control of the radiated sound power from a submarine excited by propeller forces, Journal of Ship Research, 57, 1–13 (2013)
Active Control Strategies
Internal Mass Isolation
Peters, Kinns, Kessissoglou, Effects of internal mass distribution and its isolation on the acoustic characteristics of a submerged hull, Journal of Sound and Vibration, 333, 1684‐1697 (2014)
Intensity‐Based Numerical Techniques
Marburg, S., Lösche, E., Peters, H. and Kessissoglou, N. Surface contributions to radiated sound power, Journal of the Acoustical Society of America, 133 (6), 3700–3705, (2013).
Acoustic impedance matrix
Eigenvalue decomposition
Acoustic radiation modes
Non-negative intensity
• Non‐negative intensity based on the boundary element method
100 Hz
• Hybrid computational fluid dynamics (CFD) / boundary element model (BEM)• A CFD model is used to predict the hydrodynamic flow field • Acoustic sources are extracted from the CFD data• Acoustic sources then applied to a boundary element model of the body to predict the scattered field
• A technique has been developed to reduce the amount of CFD data and accelerate the calculation of the acoustic wave propagation to the BEM surface
Croaker, Kessissoglou, Kinns, Marburg, Fast low‐storage method for evaluating Lighthill’s volume quadrupoles, AIAA Journal, 51, 867‐885 (2013)
Flow Induced Noise
• Hybrid Reynolds Averaged Navier‐Stokes (RANS) ‐ boundary element method (BEM) technique• Statistical noise sources extracted from steady state RANS data; BEMs used to predict the scattered
sound field produced by these statistical noise sources
Croaker, Karimi, Doolan, Kessissoglou, Prediction of low Mach number flow induced noise using a hybrid RANS‐BEM technique, Journal of Sound and Vibration (under review)
Hybrid RANS‐BEM Technique
2D Plate excited by Vortex Shedding
Radiated Sound
• Continuous and discrete structures are modelled using a periodic boundary element method
• For periodic structures, the nodal coordinates for the entire structure can be extracted from the nodal coordinates of a unit cell
Karimi, Croaker, Kessissoglou, Boundary element solution for periodic acoustic problems, International Journal for Numerical Methods in Engineering (under review)
Periodic Boundary Element Method
Discontinuous periodic structureContinuous periodic structure
Sonic Crystal Noise Barriers
• A sonic crystal noise barrier can be modelled using the periodic BEM technique (SPL in dB at 265 Hz)
Facilities
4’ × 3’ closed circuit wind tunnel
4’ × 3’ wind tunnel test section
18” wind tunnel
64 Channel ArrayBeamforming/NAH
Acoustic and flow Instrumentation:• Beamforming arrays• Hot‐wire anemometry• Laser diagnostics• Surface pressure• High‐channel‐count DAQ systems
Instrumentation
Owl‐inspired quiet airfoils
Wind Tunnel Testing
Controlled fan/turbine testing: beamforming
RMS
Phase Averaged
Wall‐Mounted Finite Airfoils
Flow
CFD
Experimental campaign performed in the Virginia Tech Stability Wind Tunnel
3 kHz 60 m/s, 0⁰
3.55 kHz 60 m/s, 0⁰
Test model
Microphonearray
Wall Mounted Cylinder
Flow
Flow
Trailing vortex
Separation line
Wavelet analysis at z/L = 0.8 : bimodal shedding
Sub‐boundary layer steps
LES
Experiment
Experimental Time Reversal for Aeroacoustics
RMS Time Reversal Localisation
Anechoic Wind Tunnel Experiment
Line Array
Line Array
Cylinder in Cross‐Flow
Dipole Source Field Revealed
Machine Condition Monitoring and Diagnostics
Bob Randall and Zhongxiao Peng
Research Areas
• Diagnostics of gears and bearings• Diagnostics of internal combustion engines• Simulation of faults in gears, bearings, engines• Diagnostics under varying speed and load conditions
(wind turbines)• Phase demodulation based order tracking• Operational modal analysis• Combining vibration with oil analysis
WIND TURBINE GEARBOX – Use of SKBarszcz & Randall MSSP
Spectral kurtos is in 9-11kHz band
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7-06 17-06 27-06 7-07 17-07 27-07 6-08 16-08
Date
Kur
tosi
s
Spectrum
kurtogram
Optimally filtered signal
Trend of normal kurtosis
Trend of spectral kurtosisCould have been detected earlier
Tooth damage
Helicopter Gearbox Bearing
Simulation and Diagnostics of IC Engine FaultsDr Jian ChenMisfire diagnostics
Crankshaft torsional vibration
Block rotational acceleration
Piston slap (FE model)
Bearing knock (Reynolds equation)
Inertia properties of engine components
Phase demodulation based order tracking
by phase demodulation
Resample from uniform time to uniform phase intervals
Maximum speed range is 2:1 (first harmonic) so use overlapping windows
Segment 1 Segment 5
Machine Run-up divided into five segments
Tacho signal before and after order tracking
Order tracking of Run-up signal
Five order-tracked segments overlaid
Order spectrum of response signal
Spectrograms before and after order tracking
The Cepstrum – Inverse FT of a Log Spectrum
Comparison with the autocorrelation – both are a “spectrum of a spectrum”
Echo removal in complex cepstrum
Cepstra
Spectra
Removal of high speed shaft effects
Enhancement of modal information using an exponential “lifter” (gas turbine signal)
0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1-0.02
00.020.040.06
0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10
0.5
1
0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1-0.02
00.020.040.06
Time (s)
0 0.5 1 1.5 2 2.5 3 3.5 4
x 104
101
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104
Frequency (Hz)
0 0.5 1 1.5 2 2.5 3 3.5 4
x 104
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Frequency (Hz)
(a)
(b)
(c)
(e)
(d)
(a) Cepstrum (from (d))(b) Shortpass lifter(c) Liftered cepstrum(d) Original log spectrum(e) Liftered spectrum (from (c))
