Forced excitation (loudspeakers) Fluid-loaded steady-state vibration (vibrating plates, shells) Acoustic waves impinging on structures (submarines)
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vibrating plate
fluid u
plate u
fluid u plate if r 0 : u fluid u plate if r 0 : u
Webinar Title – Month Year – See View>Slide Master to change Improving Acoustic Performance
Acoustic Analysis in Abaqus
2011 Feb web-training Simutech ution Corporation
Agenda
Acoustic Analysis in Abaqus
Structural Acoustic Applications Acoustic Problem Types Possible with Abaqus Acoustic 名詞解釋 Acoustic analysis的準備事項 Acoustic Analysis建模指引 Examples
Example of Volumetric Acceleration
A horizontal, flat rigid plate oscillating vertically imposes an acceleration on the acoustic fluid. An acoustic load is equal to this acceleration times the surface area of the plate. The load is the acceleration of a fluid particle if the volumetric drag (r) is zero.
Volumetric drag (r) is related to material impedance (Zmat) by the following relationship :
r
2 Re Z mat Im Z mat Kf
The imaginary part affects the pressure amplitude. The real part affects the wavelength.
Such flow resistance effects are commonly characterized in the frequency domain by a complex, frequency-dependent:
Density Impedance
or
Propagation constant
Acoustics Terminology
Volumetric drag
The medium supporting acoustic waves may be flowing through a porous matrix.
Examples: fiberglass used for sound deadening, ultrasonic sound in the human body
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Acoustic Problem Types Possible with Abaqus
Uncoupled acoustics problems (pure acoustics problems)
Piezoelectric
Tire noise
Underwater
Courtesy: Honeywell FM&T
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Air and other gases Water and other liquids Solid media, if:
– Shear is unimportant compared to dilatational stresses. – Example: some soils or rubber structures, especially in small-vibration analysis.
Modal solution methods (Abaqus/Standard only)
Eigenfrequency extraction
– Both uncoupled and fully coupled mode extraction
Modal dynamic analysis
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Acoustic analysis的準備事項
General Capabilities
Acoustic element Structural-acoustic interface coupling elements Acoustic infinite elements
Tetrahedral element model with one‐eighth symmetry
Transmission loss of a body due to surface effects
Impedance
The acoustic impedance, Zn, is defined as the ratio of acoustic pressure to the associated particle speed in a certain direction:
Interior sound problems (automobiles, airplanes, rooms) Exterior sound propagation problems (radiation from machinery, engines)
Coupled structural-acoustics problems
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2
Structural Acoustic Applications
Engine noise Human perception and comfort Architectural acoustics Design and analysis of electro-acoustic systems Underwater applications Vibrations of structures interacting with fluids
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Acoustics Terminology
Volumetric Acceleration
Acoustic load due to acoustic particle motion fluid
General Capabilities
Acoustic medium and surface properties
Material properties may be dependent on temperature, and/or on user-defined field variables.
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Acoustic 名詞解釋
Acoustics Terminology
What is impedance (physically)?
Solution procedures
Direct solution methods
Transient dynamic analysis (Abaqus/Standard and Abaqus/Explicit) Steady-state dynamic analysis (Abaqus/Standard only)
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General Capabilities
Boundary conditions
Nonreflecting boundary conditions for the following domains, with or without volumetric drag effects
Acoustic Problem Types Possible with Abaqus