Modelling a Structural-Acoustic Coupled System with an Equivalent Lumped Parameter Mechanical System

1999 ◽  
Vol 121 (4) ◽  
pp. 453-459 ◽  
Author(s):  
S. M. Kim ◽  
M. J. Brennan
Keyword(s):  
Coupled System ◽  
Acoustic Mode ◽  
Physical Parameters ◽  
Acoustic System ◽  
Acoustic Modes ◽  
Lumped Parameter ◽  
Resonance Frequencies ◽  
Mechanical Models ◽  
Equivalent Mass ◽  
Physical Insight

This paper describes the way in which a structural acoustic coupled system can be modelled using an equivalent lumped parameter mechanical model. The impedance-mobility approach is first used to model the system, and by relating the physical parameters to equivalent mass and stiffness, lumped parameter models can be derived provided that damping in the acoustic system is neglected in all modes, but the first (zero order) mode. A limitation of this approach, however, is that these simple mechanical models formulated in terms of the uncoupled structural and acoustic modes are only possible for either a single structural mode coupled to many acoustic modes, or a single acoustic mode coupled to many structural modes. These models facilitate physical insight into the dynamic behavior of a lightly-damped structural-acoustic system at frequencies close to the resonance frequencies of the coupled system.

Damping Performance of Material Candidates for Service at 350K

2021 ◽  
Vol 315 ◽  
pp. 43-49
Author(s):  
Si Bin Zhang ◽  
Ze Chao Jiang ◽  
Qing Chao Tian
Keyword(s):  
Internal Friction ◽  
Single Phase ◽  
Vibration Reduction ◽  
Physical Parameters ◽  
Heating Rates ◽  
Friction Mechanism ◽  
Obvious Effect ◽  
Negative Linear Correlation ◽  
Resonance Frequencies ◽  
Damping Materials

Vibration systems require the damping materials operating at high service temperature. In this paper, damping performance of HT100, M2052 and S316L at 350K were evaluated by applying different frequencies, strain amplitudes and heating rates. It is found that the internal friction dependence of frequency of HT100, M2052 and S316L all show a characteristic of Check function, and the resonance frequency has a negative linear correlation with the material physical parameters. The strain amplitude as well as heating rate has no obvious effect on the resonance frequencies of the materials, but significantly enhance the internal friction of the interface damping alloys such as M2052 and HT100, but small on single-phase alloys such as S316L. The internal friction mechanism for HT100 and M2052 are of static hysteresis at 350K, and HT100 and M2052 are applicable candidates for working at temperatures around 350K from the viewpoint of vibration reduction.

An Experimental Investigation of High Level Vibration on the Residual Heat Removal Line of a Pressurized Water Reactor

2009 ◽  
Author(s):  
Jeffrey A. Brown ◽  
Robert D. Blevins ◽  
H. Joseph Fernando
Keyword(s):  
Heat Removal ◽  
Coupled System ◽  
Acoustic Resonance ◽  
Acoustic Mode ◽  
Side Branch ◽  
Pressurized Water Reactor ◽  
Pressurized Water ◽  
Water Reactor ◽  
High Level ◽  
Residual Heat

This paper presents the results of a scaled aero acoustic test that modeled a side branch resonance observed in the residual heat removal suction line of a large pressurized water reactor. Resolution of the acoustic resonance was sought by detuning the eddy shedding frequency from the fundamental side branch acoustic mode. The specific physical modifications and their ability to detune the coupled system are presented.

Azimuthal Behaviour of Self-Excited Diametral Modes of Internal Cavities

2009 ◽  
Author(s):  
K. Aly ◽  
S. Ziada
Keyword(s):  
Acoustic Mode ◽  
Free Shear Layer ◽  
Complex Flow ◽  
Complex Behaviour ◽  
Pressure Transducers ◽  
Acoustic Modes ◽  
Mode Amplitude ◽  
Temporal Phase ◽  
Internal Cavities ◽  
Shallow Cavities

The aerodynamic excitation of ducted cavity diametral modes, which are inherently antisymmetric acoustic modes, by the oscillation of the axisymmetric free shear layer gives rise to complex flow-sound interaction mechanisms, in which the acoustic diametral modes do not possess a preferred azimuthal orientation. The azimuthal behaviour of this self-excitation mechanism is investigated experimentally. The study is performed for axisymmetric shallow cavities in a duct for a range of cavity length to depth ratio of L/d = 1 to 4, and for Mach numbers up to 0.4. Three pressure transducers flush mounted to the cavity floor are used to determine the acoustic mode amplitude and orientation. The excited acoustic modes are classified into spinning, partially spinning and stationary diametral modes. An analytical model based on the superposition of two orthogonal modes with 90° temporal phase shift is developed to reproduce the spinning and the partially spinning diametral modes. The developed model clarifies the observed complex behaviour of the azimuthal modes.

SPECTRAL PROPERTIES OF AN ELASTIC ROD-SPRING COUPLED SYSTEM IMMERSED IN A FLUID

1992 ◽  
Vol 02 (04) ◽  
pp. 441-460 ◽  
Author(s):  
J. SANCHEZ-HUBERT ◽  
S. BÉRÉTÉ ◽  
J. PLANCHARD
Keyword(s):  
Heat Exchangers ◽  
Spectral Properties ◽  
Nuclear Reactor ◽  
Dynamical Behavior ◽  
Coupled System ◽  
Elastic Tube ◽  
Elastic Rod ◽  
Resonance Frequencies ◽  
Continuous Material ◽  
Very High

The study of vibrations of elastic tube bundles immersed in a fluid is very important in Engineering, for example concerning the dynamical behavior of heat exchangers, nuclear reactor cores, etc. This paper is concerned with the investigation of the resonance frequencies when the number of rods is very high. That requires us to use the homogenization technique for modelling this coupled system by an equivalent continuous material. We then show that this equivalent system may have an essential spectrum.

scholarly journals Vibro-acoustic analysis of a trapezoidal cavity with a clamped flexible wall

2018 ◽  
Vol 37 (4) ◽  
pp. 801-815 ◽  
Author(s):  
Yuan Wang ◽  
Jianrun Zhang ◽  
Xinzhou Zhang ◽  
Bo Wu
Keyword(s):  
Acoustic Analysis ◽  
Coupled Model ◽  
Coupled System ◽  
Coupling Theory ◽  
Incident Plane ◽  
Resonance Frequencies ◽  
Modal Coupling ◽  
Cavity Coupling ◽  
Flexible Wall ◽  
Matching Degree

The coupled model between trapezoidal cavity and its clamped flexible wall is developed using classical modal coupling theory. Based on the coupled model, the resonance frequencies of coupled system are obtained and compared with the corresponding uncoupled one. Meanwhile, the reason for the variation of resonance frequencies of coupled system modes is analyzed in detail. Then, the response of coupled system is investigated using the acoustic potential energy in the cavity and panel vibration kinetic energy when it is excited by an incident plane wave outside of the cavity. Coupling coefficient between trapezoidal cavity and its clamped flexible wall is proposed to assess the modal matching degree between them. It is shown that the coupling selection is not satisfied except in the axis direction which is parallel to the inclined wall. In addition, a rectangular cavity with a clamped flexible wall is also considered and compared with that of the trapezoidal one.

scholarly journals Analytical Modelling of Three-Dimensional Squeezing Nanofluid Flow in a Rotating Channel on a Lower Stretching Porous Wall

2014 ◽  
Vol 2014 ◽  
pp. 1-14 ◽  
Author(s):  
Navid Freidoonimehr ◽  
Behnam Rostami ◽  
Mohammad Mehdi Rashidi ◽  
Ebrahim Momoniat
Keyword(s):  
Differential Equations ◽  
Ordinary Differential Equations ◽  
Volume Fraction ◽  
Three Dimensional ◽  
Porous Wall ◽  
Coupled System ◽  
Physical Parameters ◽  
Nonlinear Ordinary Differential Equations ◽  
Suction Parameter ◽  
Rotating Channel

A coupled system of nonlinear ordinary differential equations that models the three-dimensional flow of a nanofluid in a rotating channel on a lower permeable stretching porous wall is derived. The mathematical equations are derived from the Navier-Stokes equations where the governing equations are normalized by suitable similarity transformations. The fluid in the rotating channel is water that contains different nanoparticles: silver, copper, copper oxide, titanium oxide, and aluminum oxide. The differential transform method (DTM) is employed to solve the coupled system of nonlinear ordinary differential equations. The effects of the following physical parameters on the flow are investigated: characteristic parameter of the flow, rotation parameter, the magnetic parameter, nanoparticle volume fraction, the suction parameter, and different types of nanoparticles. Results are illustrated graphically and discussed in detail.

Three-Dimensional Electromechanical Impedance Model for Damaged Beams with Imperfectly Bonded Piezoelectric Patches

2011 ◽  
Vol 52-54 ◽  
pp. 1285-1290
Author(s):  
Wan Chun Li ◽  
Wei Yan ◽  
Wei Wang
Keyword(s):  
Crack Depth ◽  
Damage Index ◽  
Three Dimensional ◽  
Adhesive Layer ◽  
Coupled System ◽  
Physical Parameters ◽  
Cracked Beam ◽  
Electromechanical Impedance ◽  
Lag Model ◽  
Peel Stress

Dynamic analysis is conducted for a cracked beam with imperfectly bonded piezoelectric patches using the finite element method in the paper. The property of adhesive between the PZT patches and the host beam is taken into account based on the peel stress model as well as the shear lag model and thus the three-dimensional (3D) model of piezoelectric patch-adhesive-host beam coupled system is developed. Based on the established three-dimensional EMI model, the effect of some physical parameters such as vibration mode of main structure, the mass of adhesive layer and crack depth etc. on electromechanical impedance signatures is investigated. Finally, the root-mean-square deviation (RMSD), a kind of non-parametric damage index, is also employed to identify the damage severity of the cracked beam.

Finite-wavelength scattering of incident vorticity and acoustic waves at a shrouded-jet exit

2008 ◽  
Vol 612 ◽  
pp. 407-438 ◽  
Author(s):  
ARNAB SAMANTA ◽  
JONATHAN B. FREUND
Keyword(s):  
Mach Number ◽  
Acoustic Waves ◽  
Vortex Sheet ◽  
Acoustic Mode ◽  
Uniform Flow ◽  
Sharp Edge ◽  
Potential Mechanism ◽  
Ambient Flow ◽  
Acoustic Modes ◽  
Cylindrical Vortex

As the vortical disturbances of a shrouded jet pass the sharp edge of the shroud exit some of the energy is scattered into acoustic waves. Scattering into upstream-propagating acoustic modes is a potential mechanism for closing the resonance loop in the ‘howling’ resonances that have been observed in various shrouded jet configurations over the years. A model is developed for this interaction at the shroud exit. The jet is represented as a uniform flow separated by a cylindrical vortex sheet from a concentric co-flow within the cylindrical shroud. A second vortex sheet separates the co-flow from an ambient flow outside the shroud, downstream of its exit. The Wiener–Hopf technique is used to compute reflectivities at the shroud exit. For some conditions it appears that the reflection of finite-wavelength hydrodynamic vorticity modes on the vortex sheet defining the jet could be sufficient to reinforce the shroud acoustic modes to facilitate resonance. The analysis also gives the reflectivities for the shroud acoustic modes, which would also be important in establishing resonance conditions. Interestingly, it is also predicted that the shroud exit can be ‘transparent’ for ranges of Mach numbers, with no reflection into any upstream-propagating acoustic mode. This is phenomenologically consistent with observations that indicate a peculiar sensitivity of resonances of this kind to, say, jet Mach number.

Excitation of geodesic acoustic mode continuum by drift wave turbulence

2012 ◽  
Vol 78 (6) ◽  
pp. 651-655 ◽  
Author(s):  
JUN YU ◽  
J. Q. DONG ◽  
X. X. LI ◽  
D. DU ◽  
X. Y. GONG
Keyword(s):  
Growth Rate ◽  
Acoustic Mode ◽  
Kinetic Approach ◽  
Wave Turbulence ◽  
Ion Temperature ◽  
Drift Wave Turbulence ◽  
Acoustic Modes ◽  
Drift Wave ◽  
Radial Structure ◽  
Geodesic Acoustic Mode

AbstractExcitation of the geodesic acoustic mode continuum by drift wave turbulence is studied using the wave kinetic approach. For a model profile of weak non-uniform ion temperature, the forms of growth rate and radial structure of geodesic acoustic modes are obtained analytically. The growth rate is analyzed for several conditions for present-day tokamaks and compared with that for uniform ion temperature, as well as that given by the coherent mode approach for non-uniform ion temperature.

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