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Acoustic Engineering Overview
Presented to:Center for Acoustics and Vibration
Penn State University
Presented by:
Mike ThielSenior Engineer, Ship Signatures
May 9, 2011Approved for Public Release
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What is Electric Boat?
Designer and builder of nuclear submarines for the US Navy Large and very diverse engineering and design organization
Naval architecture Mechanical Electrical Software Electronic systems Materials Fluid Mechanics / Dynamics Structural Acoustic Fluid systems / HVAC Production / Manufacturing / Process
Program / Project Management Technology Integrator
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A Nuclear Submarine Is the Ultimate “System of Systems”
VIRGINIA Class:• 377’ long, 34’ diameter, 7835 tons• Dives deeper than 800’• Exceeds 25 knots underwater• Missions in excess of 90 days• Crew complement of 113• 12 cruise missile tubes• 4 torpedo tubes• 9 man SOF lock-out trunk• And houses a nuclear power plant
“ A Crown Jewel in America’s Arsenal”Defense Science Board, 1998
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EB is a Full Service Provider of Acoustic Services to the Submarine Navy
Science & Technology
Research, Development, Test & Evaluation
Concept Formulation
Design & Design Review
Construction & Audit
Test & Trials
Fleet Support
•Hydroacoustic research & tools•Structural acoustic research & tools
•Component development•Noise Control feature & tech. development•Test & Evaluation programs
•Ship systems design & analysis•Structural acoustic design / analysis•Hydroacoustic design / analysis•Spec development•Drawing development•Component criteria / specs•Vendor oversight
•Inspections•Design changes•Noise Review Program•Component PIT
•Dockside tests•Acoustic survey•Underway trials•Problem evaluations•Develop & test solutions
•Respond to fleet deficiencies•Test & Evaluation•Problem resolution•Backfit design•Support NAVSEA trials
•Develop new technologies•Support ship concept development•Integration of new technologies
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Our Work is Focused on Five Sub-Disciplines
Advanced Concepts
Structural Acoustics
Testing & Noise Reduction Program
Systems & Components
Hydro-acoustics
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Advanced Concepts•Technology Development and Demonstration
•Future Platform Concept Formulation (CONFORM)
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Structural Acoustics
Analysis of ship structures using Finite element, Statistical energy, and analytic methods Calculate transfer functions for
vibration and sound propagation Wavenumber decomposition to
enhance understanding of transmission mechanisms
Estimate benefits of noise control features
Validate methods by comparison to test data
Provide design guidance
(A)
S. Gavin, THE WAVENUMBER SPECTRA OF VIBRATIONS ON A RIB STIFFENED CYLINDER, Pennsylvania State University, 2003
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Computational Structural Acoustics
Example: Fluid-loaded Elastic Sphere
Elastic Sphere (Shell Finite Elements)
Radiation Boundary Condition (Acoustic Infinite Elements)
Near-field Fluid Mesh (Acoustic Finite Elements)
Reference:
Botelho, R. M., M. J. Butler, J. F. Waters, “Numerical study of fluid loading approximations for submerged spherical shells using finite, infinite and boundary element methods,” 149th
Meeting of Acoustical Society of America, May 16-20 2005.
Frequency Response for Maximum Field Pressure
Frequency Dependence of Fluid Loading
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Computational Structural Acoustics (Cont.)
Fluid-loaded Elastic Sphere with Uniform Pressure Loading
Breathing Motions of the Spherical Shell Acoustic Monopole for the Field Pressure
Fluid-loaded Elastic Sphere with a Point Force N=2 Response for the low frequency resonance N=4 Response for the mid-frequency resonance
Low Frequency Mid-frequency
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When You Model Something as Complex as a Submarine, Interpretation is Challenging and the Lessons Learned are Very Valuable
(A)
S. Gavin, THE WAVENUMBER SPECTRA OF VIBRATIONS ON A RIB STIFFENED CYLINDER, Pennsylvania State University, 2003
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Hydroacoustics – Flow Noise
Buoyant Vehicle Testing inCollaboration with NSWCTo Assess Flow Noise
CFD Simulation & Design of Flow Exposed StructuresTo Avoid Flow Tones
Acoustic Wind Tunnel at NUWC SupportsQuiet Design of Flow Exposed Bodies
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Performance Goal
Path 1
+
+
+Path m
Component 1
Component k
Whole Ship Model
Allowable Source
Speed 1Speed 2Speed n
Condition 1
Condition jComponent 1
Condition 1
Component k
Achievable Criteria
Condition 1
Condition jComponent 1
Condition 1
Component k
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Speed n
Speed 1Speed 2
Plug criteria back into whole ship model and predict as-designed performance
Predicted Performance
Generate Component Criteria Based on Allowable Source
Levels and Achievability
We Combine Analyses of Hundreds of Sources and Transmission Paths Into an Iterative Submarine Noise Prediction Model
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Shipyard Testing and SupportShipyard Testing
•Reactor Plant Testing
•Component Pre-Installation Testing
•Problem diagnosis
Shipyard Support
•Review Construction Deficiencies
•Analyses to demonstrate acceptable deviations from plan
•Monitoring of quality control
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At-Sea Testing
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Summary EB designs & builds a very challenging and
complex product…the nuclear submarine We collaborate heavily with Navy labs and
other businesses Acoustics is integrated into the entire R&D,
design and construction process as a key attribute
Empirical and numerical tools are used to estimate noise sources and noise transmission characteristics