Experimental Verification of the Asymptotic Modal Analysis Method as Applied to a Rectangular Acoustic Cavity Excited by Structural Vibration

1992 ◽  
Vol 114 (4) ◽  
pp. 546-554 ◽  
Author(s):  
L. F. Peretti ◽  
E. H. Dowell
Keyword(s):  
Modal Analysis ◽  
Sound Pressure ◽  
Power Spectra ◽  
Rigid Wall ◽  
Structural Vibration ◽  
Flexible Plate ◽  
Acoustic Cavity ◽  
Rigid Walls ◽  
End Wall ◽  
Good Agreement

An experiment was performed on a rigid wall rectangular acoustic cavity driven by a flexible plate mounted in a quarter of one end wall and excited by white noise. The experiment was designed so that the assumptions of Asymptotic Modal Analysis (AMA) were satisfied for certain bandwidths and center frequencies. Measurements of sound pressure levels at points along the boundaries and incrementally into the interior were taken. These were compared with the theoretical results predicted with AMA, and found to be in good agreement, particularly for moderate (1/3 octave) bandwidths and sufficiently high center frequencies. Sound pressure level measurements were also taken well into the cavity interior at various points along the 5 totally rigid walls. The AMA theory, including boundary intensification effects, was shown to be accurate provided the assumption of large number of acoustic modes is satisfied, and variables such as power spectra of the wall acceleration, frequency, and damping are slowly varying in the frequency bandwidth.

Structural-Acoustic Responses of a Coupled Panel Cavity System Using a Deterministic-Statistical Approach

2015 ◽  
Author(s):  
Renqiang Jiao ◽  
Jianrun Zhang ◽  
Fei Xue ◽  
Xin Liao ◽  
Xin Liu
Keyword(s):  
Sound Pressure ◽  
Pressure Response ◽  
Structural Vibration ◽  
Response Analysis ◽  
Flexible Plate ◽  
Concentrated Force ◽  
Acoustic Cavity ◽  
Cavity System ◽  
Elastically Restrained Edges ◽  
Acoustic Responses

The coupled panel cavity system composed of an acoustic space and a wall surface is a reasonable representation of many engineering applications. A good understanding of the structural-acoustic interaction between the structural vibration and sound pressure response inside the cavity is of critical importance to, for instance, the control of sound fields in car compartments, airplane and ship cabins, etc. Motivated by above, an investigation on the structural-acoustic responses of a coupled panel cavity system is presented. A rectangular acoustic cavity bounded by a flexible panel with elastically restrained edges is examined. In this paper, for the so called “mid-frequency” problem, a hybrid deterministic and statistic approach is employed to overcome the defects in application of pure deterministic or statistical methods. Then the vibration and interior sound pressure response analysis for the panel-cavity system are conducted using this method under external normal concentrated force acting at the flexible plate. Finally, comparisons between the numerical and test results are presented and the relevant frequency ranges for which the hybrid deterministic and statistical approaches work in are discussed for the given structure.

Global Active Control of Transmitted Sound Into Acoustic Cavity With Speakers and Piezoelectric Patch Actuators

2009 ◽  
Author(s):  
Masih Hanifzadegan ◽  
Abdolreza Ohadi
Keyword(s):  
Active Control ◽  
Plane Waves ◽  
Sound Field ◽  
Coupled System ◽  
Mode Shapes ◽  
Flexible Plate ◽  
Acoustic System ◽  
Acoustic Cavity ◽  
Piezoelectric Patch ◽  
Rigid Walls

In this work modeling of a vibro-acoustic system and global sound field control with both acoustic and structural actuators have been studied. The model of the system consists of a 3D rectangular cavity with five acoustically rigid walls and a flexible plate on the top of cavity. First, modeling of the vibro-acoustic system has been acquired and subsequently the mode shapes and natural frequencies of the coupled system have been calculated. Plane waves on the plate surface are the main sources of disturbances in this system. Undesired sound (noise) which is propagated into the enclosure is controlled by mounted piezoelectric patch actuators on the plate and acoustic piston sources (speakers) inside cavity. The global active control is designed to minimize the acoustic potential energy inside the cavity. The control performance has been investigated by acoustic and structural actuators separately and simultaneously.

Low Frequency Acoustic Performance of Close-Fitting Sandwich Panels

1998 ◽  
Vol 5 (3) ◽  
pp. 143-161 ◽  
Author(s):  
W.C. Tang ◽  
C.F. Ng
Keyword(s):  
Porous Material ◽  
Low Frequency ◽  
Coupled System ◽  
Sound Insulation ◽  
Flexible Plate ◽  
Cavity Depth ◽  
Acoustic Cavity ◽  
Air Cavities ◽  
Rigid Walls ◽  
Double Wall

The experiment presented in this paper was to investigate and analyse the noise reduction at low frequency of porous material used to line the cavity between two panels of a double-panel structure. The effects of panel construction, fibreglass and cavity depth have also been studied. The structural-acoustic coupled system of a sandwich structure, backed by a rectangular acoustic cavity of rigid walls is discussed. It is found that the sound insulation of a combination of a stiff thick and a thin flexible plate panel, with air cavities and porous material in-between, is more effective than that of the conventional double-wall panel at low frequency.

Effect of Boundary Layer Suction on Aerodynamic Performance of High-Turning Compressor Cascade

2013 ◽  
Author(s):  
Longxin Zhang ◽  
Shaowen Chen ◽  
Hao Xu ◽  
Jun Ding ◽  
Songtao Wang
Keyword(s):  
Experimental Data ◽  
Boundary Layer ◽  
Experimental Studies ◽  
Aerodynamic Performance ◽  
Parameter Distribution ◽  
Compressor Cascade ◽  
Boundary Layer Suction ◽  
End Wall ◽  
Low Speed Wind Tunnel ◽  
Good Agreement

Compared with suction slots, suction holes are (1) flexible in distribution; (2) alterable in size; (3) easy to fabricate and (4) high in strength. In this paper, the numerical and experimental studies for a high turning compressor cascade with suction air removed by using suction holes in the end-wall at a low Mach numbers are carried out. The main objective of the investigation is to study the influence of different suction distributions on the aerodynamic performance of the compressor cascade and to find a better compound suction scheme. A numerical model was first made and validated by comparing with the experimental results. The computed flow visualization and exit parameter distribution showed a good agreement with experimental data. Second, the model was then used to simulate the influence of different suction distributions on the aerodynamic performance of the compressor cascade. A better compound suction scheme was obtained by summarizing numerical results and tested in a low speed wind tunnel. As a result, the compound suction scheme can be used to significantly improve the performance of the compressor cascade because the corner separation gets further suppressed.

scholarly journals Unsteady pressure measurement and numerical simulations in an end-wall region of a linear blade cascade

2021 ◽  
Vol 3 (8) ◽  
Author(s):  
Erik Flídr ◽  
Petr Straka ◽  
Milan Kladrubský ◽  
Tomáš Jelínek
Keyword(s):  
Numerical Simulations ◽  
Pressure Measurement ◽  
Power Spectra ◽  
Surface Flow ◽  
Wall Region ◽  
Suction Surface ◽  
Flow Angle ◽  
Unsteady Pressure ◽  
Flow Visualizations ◽  
End Wall

AbstractThis contribution describes experimental and numerical research of an unsteady behaviour of a flow in an end-wall region of a linear nozzle cascade. Effects of compressibility ($$M_\mathrm {2,is}$$ M 2 , is ) and inlet flow angle ($$\alpha _1$$ α 1 ) were investigated. Reynolds number ($$Re_\mathrm {2,is}$$ R e 2 , is $$=8.5\times 10^5$$ = 8.5 × 10 5 ) was held constant for all tested cases. Unsteady pressure measurement was performed at the blade mid-span in the identical position $${\mathfrak {s}}$$ s to obtain reference data. Surface flow visualizations were performed as well as the steady pressure measurement to support conclusions obtained from the unsteady measurements. Comparison of the surface Mach number distributions obtained from the experiments and from the numerical simulations are presented. Flow visualizations are then compared with calculated limiting streamlines on the blade suction surface. It was shown, that the flow structures in the end-wall region were not affected by the primary flow at the blade mid-span, even when the shock wave formed. This conclusion was made from the experimental, numerical, steady as well as unsteady points of view. Three significant frequencies in the power spectra suggested that there was a periodical interaction between the vortex structures in the end-wall region. Based on the data analyses, anisotropic turbulence was observed in the cascade.

The Elucidation of Mechanism of Local Sound Pressure Increase Phenomenon

2004 ◽  
Author(s):  
Reiko Koganei ◽  
Shigemasa Ando ◽  
Qinzhong Shi ◽  
Ichiro Hagiwara
Keyword(s):  
Structural Damage ◽  
Sound Pressure ◽  
Pressure Increase ◽  
Narrow Gap ◽  
Local Pressure ◽  
Acoustic Environment ◽  
Space Instruments ◽  
Acoustic Cavity ◽  
Lift Off ◽  
Component Interface

Payloads of satellite are exposed on the severe acoustic environment at the process of lift-off and supersonic zone of a launcher. This acoustic environment excites the payload in high pressure and broad frequency band of random acoustical excitation, which may cause serious damage to the structures or instruments of the spacecraft inside. Space instruments are designed and verified to the acoustic environment by ground reverberant acoustic chamber in order to specify random vibration level at component interface and to verify the payloads are working in function and the structure does not have structural damage. The present load sound pressure specification assumes that the sound pressure interior fairing is uniformly distributed. In spacecraft system acoustic tests, local pressure increase occurs in the narrow gap between spacecraft primal structure and components facing toward the fairing wall. This acoustical environment load to the components differs from that the components were tested alone and the flight acoustic environment may not be actually simulated in the ground testing. It is important to clarify the mechanism of sound pressure increase in the narrow gap in order to predict the level of sound pressure increase. In this study, we focus to the investigation of the mechanism by basic experiment including acoustic testing and vibration modal survey. It is clarified that the main reason of the phenomenon is dominated by the acoustic cavity on the appropriate boundary condition rather than structure vibration. And more, we predict the frequency at which the sound pressure increase at the narrow gap and compare analysis results with experiment results by using Boundary Element Method (BEM).

Sound absorption of a finite flexible micro-perforated panel absorber back by a rigid air cavity filled with a fibrous porous material

2021 ◽  
Vol 263 (3) ◽  
pp. 3625-3632
Author(s):  
Ho Yong Kim ◽  
Yeon June Kang
Keyword(s):  
Energy Dissipation ◽  
Porous Material ◽  
Fibrous Material ◽  
Alternative Energy ◽  
Sound Absorption ◽  
Sound Pressure ◽  
Absorption Coefficients ◽  
Air Cavity ◽  
Acoustic Cavity ◽  
Absorption Performance

Back by a rigid cavity filled with a layer of porous layer, the sound absorption performance of a micro-perforated panel (MPP) can be enhanced in comparison with other resonance based sound absorbers. In this paper, a theoretical model of a finite flexible MPP back by a rigid air cavity filled with a fibrous porous material is developed to predict normal sound absorption coefficients. Displacements of MPP and sound pressure field in fibrous porous material and acoustic cavity are expressed using a series of modal functions, and the sound absorption coefficients of MPP system are obtained. Additionally, comparison of energy dissipation by MPP and fibrous material is performed to identify effects of a fibrous material on the sound absorption of a MPP. As expected, at anti-resonance frequency of an MPP, the fibrous material provide an alternative energy dissipation mechanism.

scholarly journals Modal Analysis of the Structural Vibration of an Oil-hydraulic Pump.

1996 ◽  
Vol 27 (2) ◽  
pp. 315-327 ◽  
Author(s):  
Eiichi KOJIMA ◽  
Hirokazu IWATA ◽  
Norikazu HYODO ◽  
Shinji MATSUSHIMA ◽  
Kakuei WATANABE
Keyword(s):  
Modal Analysis ◽  
Structural Vibration ◽  
Hydraulic Pump

Numerical Calculation of Pressure Fluctuations in the Volute of a Centrifugal Fan

2005 ◽  
Vol 128 (2) ◽  
pp. 359-369 ◽  
Author(s):  
Rafael Ballesteros-Tajadura ◽  
Sandra Velarde-Suárez ◽  
Juan Pablo Hurtado-Cruz ◽  
Carlos Santolaria-Morros
Keyword(s):  
Fluid Dynamics ◽  
Pressure Fluctuations ◽  
Three Dimensional ◽  
Power Spectra ◽  
Operating Conditions ◽  
Experimental Results ◽  
Time Dependent ◽  
Centrifugal Fan ◽  
Wall Pressure Fluctuations ◽  
Good Agreement

In this work, a numerical model has been applied in order to obtain the wall pressure fluctuations at the volute of an industrial centrifugal fan. The numerical results have been compared to experimental results obtained in the same machine. A three-dimensional numerical simulation of the complete unsteady flow on the whole impeller-volute configuration has been carried out using the computational fluid dynamics code FLUENT®. This code has been employed to calculate the time-dependent pressure both in the impeller and in the volute. In this way, the pressure fluctuations in some locations over the volute wall have been obtained. The power spectra of these fluctuations have been obtained, showing an important peak at the blade passing frequency. The amplitude of this peak presents the highest values near the volute tongue, but the spatial pattern over the volute extension is different depending on the operating conditions. A good agreement has been found between the numerical and the experimental results.

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