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

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+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