scholarly journals Study on acoustic radiation response characteristics of sound barriers

Open Physics ◽  
2021 ◽  
Vol 19 (1) ◽  
pp. 602-608
Author(s):  
Jiyong Jin ◽  
Congyun Zhu ◽  
Rui Wu ◽  
Yanming Liu ◽  
Miao Li
Keyword(s):  
Natural Frequencies ◽  
Acoustic Radiation ◽  
Structural Parameters ◽  
Power Level ◽  
Low Noise ◽  
Superposition Method ◽  
Noise Attenuation ◽  
Arbitrary Boundary ◽  
Attenuation Effect ◽  
Sound Barrier

Abstract The influence of acoustic radiation is considered in the prediction of noise attenuation effect of sound barrier, which provides a theoretical reference for further improving the insertion loss of sound barrier. Based on the theory of thin plate vibration, the vibration mode and natural frequencies of sound barrier under arbitrary boundary conditions are established by using two-dimensional beam function method, and the forced vibration response of the sound barrier is calculated based on the modal superposition method. MATLAB software (MathWorks Company, Natick, Massachusetts, USA) is used to calculate the natural frequencies and the radiated sound power level of the sound barrier, which indicated that the sound radiation caused by external excitation would significantly increase the sound pressure level at the received point, which should be considered as one of the influencing factors in the prediction of noise attenuation effect. The influence of diverse structural parameters on the radiated acoustic power is compared, providing an excellent reference for the design of sound barrier with low noise.

Comparative noise reduction effect of sound barrier based on statistical energy analysis

2021 ◽  
pp. 1-9
Author(s):  
Jiyong Jin ◽  
Congyun Zhu ◽  
Rui Wu ◽  
Yanming Liu ◽  
Miao Li
Keyword(s):  
Energy Analysis ◽  
Mineral Wool ◽  
Theoretical Formula ◽  
Noise Attenuation ◽  
Statistical Energy Analysis ◽  
Acoustic Source ◽  
Attenuation Effect ◽  
Sound Barrier ◽  
Absorbing Materials ◽  
Reduction Effect

In this paper, based on statistical energy analysis (SEA), the noise attenuation effect of highway sound absorbing barrier is predicted. The theoretical formula value is compared with the calculated value of statistical energy analysis (SEA) to verify its effectiveness in the prediction of sound barrier. And the insertion loss of sound barrier of mineral wool with diverse material thicknesses and coverage are calculated. The results showed that the noise attenuation of the sound barrier increased by 1.5 dB when the sound absorbing materials are attached to the sound barrier near the acoustic source. The noise attenuation effect of mineral wool is improved in the frequency band below 600 Hz when the thickness is increased. The coverage of mineral cotton increased by 25%, and the noise attenuation increased by 0.4 dB. Meanwhile, it also reflects the advantages of fast and convenient statistical energy analysis (SEA) – only one time modelling and changing its parameters can obtain the corresponding statistical results, which has some excellent reference function.

Optimal Design of Structural Parameters of Flexible Linkage Mechanisms for Noise Attenuation

2003 ◽  
Author(s):  
Xianmin Zhang ◽  
Jianwei Lu
Keyword(s):  
Optimal Design ◽  
Design Variable ◽  
Acoustic Radiation ◽  
Structural Parameters ◽  
Radiation Energy ◽  
Noise Attenuation ◽  
Variable Metric ◽  
Variable Metric Method ◽  
Weighted Measure ◽  
Flexible Linkage

Optimal design of structural parameters of flexible linkage mechanisms for noise attenuation is studied in this paper. The sum of weighted mass of the structure and weighted measure of acoustic radiation energy is taken as the performance index, and the thickness of the links of the mechanism is taken as the design variable. Optimization is carried out based on the modified constrained variable metric method. Simulation demonstrates that the proposed method is valid.

scholarly journals Numerical Analysis of Structure Acoustic Radiation Based on Wave Superposition Method

2011 ◽  
Vol 2-3 ◽  
pp. 733-738
Author(s):  
Sheng Yao Gao ◽  
De Shi Wang ◽  
Yi Qun Du
Keyword(s):  
Integral Equation ◽  
Acoustic Field ◽  
Acoustic Radiation ◽  
Boundary Surface ◽  
Impact Factors ◽  
Power Calculation ◽  
Superposition Method ◽  
Sound Power ◽  
Wave Superposition ◽  
Equivalent Sources

To overcome the non-uniqueness of solution at eigenfrequencies in the boundary integral equation method for structural acoustic radiation, wave superposition method is introduced to study the acoustics characteristics including acoustic field reconstruction and sound power calculation. The numerical method is implemented by using the acoustic field from a series of virtual sources which are collocated near the boundary surface to replace the acoustic field of the radiator, namely the principle of equivalent. How to collocate these equivalent sources is not indicated definitely. Once wave superposition method is applied to sound power calculation, it is necessary to evaluate its accuracy and impact factors. In the paper, the basic principle of wave superposition method is described, and then the integral equation is discretized. Also, the impact factors including element numbers, frequency limitation, and distance between virtual source and integral surface are analyzed in the process of calculate the acoustic radiation from the simply supported thin plate under concentrated force. The extensive measures of acoustic field at the thin plate are compared with results obtain using different numerical methods. The results show that: (a) The agreement between the results from the above numerical methods is excellent. The wave superposition method requires fewer elements and hence is faster. But the extensive numerical modeling suggests that as long as the volume velocity matching yields more than adequate accuracy. (b) The equivalent sources should be collocated inside the radiator. And the accuracy of a given Gauss integration formula will decrease as the source approaches the boundary surface. (c) The numerical method is applicable to the acoustic radiation of structure with complicated shape. (d) The method described in this paper can be used to perform effectively sound power calculation, and its application range can be extended on the basis of these conclusions.

Analysis of Modal Parameters of Adhesively Bonded Double-Strap Joints by the Modal Strain Energy Method

1993 ◽  
Author(s):  
Mohan D. Rao ◽  
Krishna M. Gorrepati
Keyword(s):  
Strain Energy ◽  
Natural Frequencies ◽  
Structural Parameters ◽  
Flexural Vibration ◽  
Mode Shapes ◽  
Modal Parameters ◽  
Adhesively Bonded ◽  
Modal Strain Energy ◽  
Joint System ◽  
Damping Material

Abstract This paper presents the analysis of modal parameters (natural frequencies, damping ratios and mode shapes) of a simply supported beam with adhesively bonded double-strap joint by the finite-element based Modal Strain Energy (MSE) method using ANSYS 4.4A software. The results obtained by the MSE method are compared with closed form analytical solutions previously obtained by the first author for flexural vibration of the same system. Good agreement has been obtained between the two methods for both the natural frequencies and system loss factors. The effects of structural parameters and material properties of the adhesive on the modal properties of the joint system are also studied which are useful in the design of the joint system for passive vibration and noise control. In order to evaluate the MSE and analytical results, some experiments were conducted using aluminum double-strap joint with 3M ISD112 damping material. The experimental results agreed well with both analytical and MSE results indicating the validity of both analytical and MSE methods. Finally, a comparative study has been conducted using various commercially available damping materials to evaluate their relative merits for use in the design of these joints.

scholarly journals Wave Based Method for Free Vibration Analysis of Ring Stiffened Cylindrical Shell with Intermediate Large Frame Ribs

2013 ◽  
Vol 20 (3) ◽  
pp. 459-479 ◽  
Author(s):  
Meixia Chen ◽  
Jianhui Wei ◽  
Kun Xie ◽  
Naiqi Deng ◽  
Guoxiang Hou
Keyword(s):  
Cylindrical Shell ◽  
Free Vibration ◽  
Boundary Conditions ◽  
Natural Frequencies ◽  
Free Vibration Analysis ◽  
Structure Type ◽  
Vibration Characteristics ◽  
Mode Shapes ◽  
Arbitrary Boundary ◽  
Stiffened Cylindrical Shell

Wave based method which can be recognized as a semi-analytical and semi-numerical method is presented to analyze the free vibration characteristics of ring stiffened cylindrical shell with intermediate large frame ribs for arbitrary boundary conditions. According to the structure type and the positions of discontinuities, the model is divided into different substructures whose vibration field is expanded by wave functions which are exactly analytical solutions to the governing equations of the motions of corresponding structure type. Boundary conditions and continuity equations between different substructures are used to form the final matrix to be solved. Natural frequencies and vibration mode shapes are calculated by wave based method and the results show good agreement with finite element method for clamped-clamped, shear diaphragm – shear diaphragm and free-free boundary conditions. Free vibration characteristics of ring stiffened cylindrical shells with intermediate large frame ribs are compared with those with bulkheads and those with all ordinary ribs. Effects of the size, the number and the distribution of intermediate large frame rib are investigated. The frame rib which is large enough is playing a role as bulkhead, which can be considered imposing simply supported and clamped constraints at one end of the cabin and dividing the cylindrical shell into several cabins vibrating separately at their own natural frequencies.

scholarly journals Identification of Mistuning Characteristics of Bladed Disks From Free Response Data

1998 ◽  
Author(s):  
Marc P. Mignolet ◽  
Alejandro Rivas-Guerra
Keyword(s):  
Dynamic Models ◽  
Natural Frequencies ◽  
Dynamic Properties ◽  
Structural Parameters ◽  
Identification Problem ◽  
Forced Response ◽  
Mode Shapes ◽  
Likelihood Principle ◽  
Bladed Disks ◽  
Block Test

The focus of the present investigation is on the estimation of the dynamic properties, i.e. masses, stiffnesses, natural frequencies, mode shapes and their statistical distributions, of turbomachine blades to be used in the accurate prediction of the forced response of mistuned bladed disks. As input to this process, it is assumed that the lowest natural frequencies of the blades alone have been experimentally measured, for example in a broach block test. Since the number of measurements is always less than the number of unknowns, this problem is indeterminate in nature. Two distinct approaches will be investigated to resolve the shortfall of data. The first one relies on the imposition of as many constraints as needed to insure a unique solution to this identification problem. Specifically, the mode shapes and modal masses of the blades are set to their design/tuned counterparts while the modal stiffnesses are varied from blade-to-blade to match the measured natural frequencies. The second approach, based on the maximum likelihood principle, yields estimates of all the structural parameters of the blades through the minimization of a specified “cost function”. The accuracy of these two techniques in predicting the forced response of mistuned bladed disks will be assessed on simple dynamic models of the blades.

Verification of the carbonate double-porosity conductivity model based on digital cores

2017 ◽  
Vol 5 (2) ◽  
pp. T173-T183 ◽  
Author(s):  
Huaimin Dong ◽  
Jianmeng Sun ◽  
Yafen Li ◽  
Likai Cui ◽  
Weichao Yan ◽  
...  
Keyword(s):  
Pore Structure ◽  
Structural Parameters ◽  
Double Porosity ◽  
Pore Network Model ◽  
Superposition Method ◽  
Conductivity Model ◽  
Model Based ◽  
Core Technology ◽  
Distribution Ranges ◽  
Digital Core

Carbonate reservoirs have complicated pore structure and reserving space, and the pore size distribution ranges are very large. Pore structure distributions represent a bimodal or trimodal state, which is also accompanied with an obviously non-Archie phenomenon. Double- and triple-porosity conductivity models based on the classification of pore dimensions were of a good coincidence with the non-Archie behavior. We have adopted digital core technology to verify the carbonate double-porosity conductivity model. Also, many rock-physical experiments and numerical simulations were performed. Through CT scanning under appropriate resolutions, macro- and micropore digital cores, which could respectively characterize the different pores, were constructed for the carbonate samples. Then the superposition method was further applied to construct the superposition digital cores, which can characterize different pores simultaneously. To quantitatively analyze and compare the effect of basic structural parameters to different digital cores, the pore network model was extracted using the Lee-Kashyap-Chu algorithm to furtherly verify the differences between scanning resolutions and pore selection characterization. In terms of qualitative validation of the double-pore conductivity model, the electrical characteristics and resistivity index (RI) under different saturations were simulated using the finite-element method and the lattice Boltzmann method. The RI curves indicated that the calculation results from the double-pore conductivity model based on a digital core are coincident with the numerical simulation results. In other words, the digital core technology can verify the double-porosity conductivity model effectively.

Simulation of the Ultrasonic Diffraction in Viscous Fluids

2003 ◽  
Author(s):  
N. Bouaoua ◽  
A. Alia ◽  
H. Djelouah
Keyword(s):  
Finite Difference ◽  
Viscous Fluid ◽  
Impulse Response ◽  
Acoustic Radiation ◽  
Viscous Fluids ◽  
Attenuation Effect ◽  
Ultrasonic Diffraction ◽  
Response Method ◽  
Good Agreement

In this paper, Impulse Response Method (IRM) and Finite Difference (FD) are used to model the acoustic radiation in a viscous fluid where the attenuation is obeying a squared frequency law. Some results are presented to illustrate the attenuation effect on the diffraction. A good agreement between the IRM results and those numerically predicted by FDM is observed.

The Research of Structural Parameters on Natural Frequency of Laminated Composite Plates

2013 ◽  
Vol 740 ◽  
pp. 461-464
Author(s):  
Fei Zhao ◽  
Jin Wu Wu
Keyword(s):  
Natural Frequencies ◽  
Structural Parameters ◽  
Orientation Angle ◽  
Laminated Composite ◽  
Composite Plates ◽  
Element Model ◽  
Laminated Composite Plates ◽  
Laminated Composite Plate ◽  
Modulus Ratio ◽  
Depth Ratio

In this paper, natural frequencies of laminated composite plates were studied. The layerwise finite element model is imposed to determine the natural frequencies of laminated composite plates. The effects of panel orientation angle, elastic modulus ratio and width-depth ratio on the natural frequencies of the laminated composite are then discussed. With an example of a sixteen-laying laminated plate, the numerical simulations show that the factor of key structural parameters to the natural frequencies of the laminated composite plate is panel orientation angle and width-depth ratio.

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