Modelling of sound radiation from a beam-stiffened plate and a clamped rectangular plate based on a modal method

2014 ◽  
Vol 228 (16) ◽  
pp. 2900-2914 ◽  
Author(s):  
Ji Woo Yoo
Keyword(s):  
Rectangular Plate ◽  
Acoustic Radiation ◽  
Radiation Power ◽  
Sound Radiation ◽  
Radiation Efficiency ◽  
Flexible Plate ◽  
Stiffened Plate ◽  
Edge Mode ◽  
Flexible Rectangular Plate ◽  
Modal Method

The farfield acoustic radiation efficiency and power of a flexible rectangular plate coupled to a relatively stiffer beam are investigated. A numerical model based on a modal method that consists of a plate with sliding edges surrounded by four stiff beams is studied. Assuming that each beam is a heavy mass, a plate with clamped edges is realised, and this model is verified. This model is then extended to a beam-stiffened plate. If the bending stiffness of the excited beam is large, the radiation efficiency increases in the corner- and edge-mode frequency regions and is higher than that of the clamped plate in terms of the averaged response for randomly selected excitations. The reason for this effect is that the corner and edge areas that radiate sound are broader because the behaviour of the plate is governed by the motion of the stiff beam. This is explained in terms of the wavenumber and the wavelength of a stiff beam and a flexible plate. It is shown that this is true only when the excitation is applied to the beam, and the radiation efficiency is similar if the plate is excited. In addition, it was found that the radiation power decreases with increasing beam stiffness because the vibration of the plate actually decreases. In addition, it was shown that the variation in the radiation efficiency of the beam-stiffened plate is smaller when the beam is excited than when the plate is excited.

scholarly journals A Comparative Study on Acoustic Optimization and Analysis of CLD/Plate in a Cavity Using ESO and GA

2018 ◽  
Vol 2018 ◽  
pp. 1-16 ◽  
Author(s):  
Dongdong Zhang ◽  
Shuwen Wang ◽  
Ling Zheng
Keyword(s):  
Boundary Conditions ◽  
Radiation Power ◽  
Sound Radiation ◽  
Computational Time ◽  
Sound Power ◽  
Normal Velocity ◽  
Flexible Plate ◽  
Rejection Ratio ◽  
Sound Radiation Power ◽  
Element Method

An acoustic radiation model of a cavity with a flexible plate treated with constrained layer damping (CLD) is developed by a combination of finite element method (FEM) and boundary element method (BEM). An acoustic topology optimization model is established with the objective of minimizing sound radiation power at specific modal frequency and design variables defined as locations of CLD treatments. The evolutionary structural optimization (ESO) method and genetic algorithm (GA) are employed to search optimal CLD configurations. Sound power sensitivity for CLD/plate is derived to determine search direction in ESO optimization procedure. The optimal CLD layouts for the flexible plate with two different boundary conditions are obtained and analyzed. Computational time, optimal layouts, and minimum sound power obtained using ESO and GA are compared. The results demonstrate effectiveness of the two methods, and ESO is more efficient to obtain deterministic and more practical optimal CLD material layouts for minimizing sound radiation power. The influences of CLD materials thickness and exciting force locations on optimal results obtained using ESO are discussed in detail. It is shown that the optimal rejection ratio varies with thicknesses of CLD materials and distribution of normal velocity of the flexible plate. Variation trend of the optimal rejection ratio is opposite for the two boundary conditions.

Research on Vibration and Sound Radiation from Submarine Functionally Graded Material Nonpressure Cylindrical Shell

2013 ◽  
Vol 690-693 ◽  
pp. 3046-3049
Author(s):  
Yan Bing Zhang ◽  
Chun Yu Ren ◽  
Xi Zhu
Keyword(s):  
Cylindrical Shell ◽  
Acoustic Radiation ◽  
Radiation Power ◽  
Sound Radiation ◽  
Functionally Graded ◽  
Underwater Sound ◽  
Graded Materials ◽  
Graded Material ◽  
Vibration And Sound Radiation ◽  
Sound Radiation Power

In this paper, we establish the finite element (FEM) and boundary element (BEM) models of a submarine section, and study the underwater sound radiation field of three different non-pressure shells made of steel, steel with anechoic tile, and the functionally graded materials (FGM) separately using a method combining of FEM and BEM . Research shows that the combination of FEM and BEM can address the acoustic radiation calculation problem of FGM, and in comparison with steel and anechoic tile laying submarine section, the weight of FGM non-pressure shell reduces 1600kg, and the sound radiation power decreases 4db and 2.5db respectively, thus having better performance in vibration and noise reduction.

scholarly journals Prediction of Sound Radiation from Submerged Cylindrical Shell Based on Dominant Modes

2020 ◽  
Vol 10 (9) ◽  
pp. 3073 ◽  
Author(s):  
Chao Zhang ◽  
Sihui Li ◽  
Dejiang Shang ◽  
Yuyuan Han ◽  
Yuyang Shang
Keyword(s):  
Cylindrical Shell ◽  
Radiation Power ◽  
Cylindrical Shells ◽  
Low Frequency ◽  
Sound Radiation ◽  
Radiation Efficiency ◽  
Frequency Sound ◽  
Comparison Results ◽  
Sound Radiation Efficiency ◽  
Sound Radiation Power

A sound radiation calculation method by using dominant modes is proposed to predict the sound radiation from a cylindrical shell. This method can provide an effective way to quickly predict the sound radiation of the structure by using as few displacement monitoring points as possible on the structure surface. In this paper, modal analyses of a submerged cylindrical shell are carried out by taking the vibration mode of a cylindrical shell in a vacuum, as a set of orthogonal bases. The modal sound radiation efficiency and modal contributions to sound radiation power are presented, and comparison results show that a few modes dominantly contribute to the sound radiation power at low frequencies. These modes, called dominantly radiated structural modes in this paper, are applied to predict the sound radiation power of submerged cylindrical shells by obtaining the modal participant coefficients and sound radiation efficiency of these dominant modes. Aside from the orthogonal decomposition method, a method of solving displacement modal superposition equations is proposed to extract the modal participant coefficients, because few modes contribute to the vibration displacement near the resonant frequencies. Some simulations of cylindrical shells with different boundaries are conducted, and the number of measuring points required are examined. Results show that this method, based on dominant modes, can well predict the low-frequency sound radiation power of submerged cylindrical shells. In addition, compared with the boundary element method, this method can better reduce the number of required measuring points significantly. The data of these important modes can be saved, which can help to predict the low-frequency sound radiation of the same structure faster in the future.

Sound Radiation Response of a Rectangular Plate Having a Side Crack of Arbitrary Length, Orientation, and Position

2015 ◽  
Vol 137 (2) ◽  
Author(s):  
Tanmoy Bose ◽  
Amiya R. Mohanty
Keyword(s):  
Rectangular Plate ◽  
Ritz Method ◽  
Sound Radiation ◽  
Radiation Efficiency ◽  
Sound Power ◽  
Cracked Plate ◽  
Side Crack ◽  
Radiated Sound ◽  
Radiated Sound Power ◽  
Element Method

Here, sound radiation characteristics of a rectangular plate having a side crack of different crack lengths, orientations, and positions are studied considering clamped boundary conditions. First, a free and forced vibration response analysis of a cracked plate is done using the Ritz method. Orthogonal polynomials are used for faster convergence and some corner functions are used to generate the effect of a crack. Radiated sound power and radiation efficiency of the cracked plate are computed by the quadruple integration. A convergence test of radiation efficiency is carried out to fix the number of polynomials and corner functions in the analysis. It is found that the radiation efficiency and radiated sound power computed by the Ritz method are close to the same obtained from the boundary element method (BEM). The natural frequencies computed using the Ritz method are also found to be close to that obtained from the finite element method (FEM). The radiation efficiency curves of different modes are shown for a change in crack length, orientation and position. Finally, the variations of normalized sound power are shown to be due to a change in the crack parameters.

scholarly journals Vibro-Acoustic Performance of a Sandwich Plate with Periodically Inserted Resonators

2019 ◽  
Vol 9 (18) ◽  
pp. 3651 ◽  
Author(s):  
Zhiwei Guo ◽  
Jie Pan ◽  
Meiping Sheng
Keyword(s):  
Band Gap ◽  
Effective Mass ◽  
Periodic Structure ◽  
Sandwich Plate ◽  
Acoustic Radiation ◽  
Radiation Power ◽  
Frequency Component ◽  
Radiation Efficiency ◽  
Closed Form Solutions ◽  
Acoustic Performance

The vibro-acoustic performance of a sandwich plate with periodic locally resonant (LR) units is examined in this paper, with specific focus on the effect of periodic resonators on the average radiation efficiency and the acoustic radiation to the far field. In order to assess the radiation performance, the band-gap properties of an infinite periodic structure and the vibrational response of a finite periodic structure are first studied with closed-form solutions. Subsequently, the acoustic radiation efficiency of the LR sandwich plate is obtained using the concepts of modal radiation. It is shown that the acoustic radiation power can be reduced significantly, not only in the band-gap but also at frequencies close below the band-gap, due to either the decrease in radiation efficiency or the decrease in the vibration response. Thus, the periodic resonators provide a broader attenuation band for the purposes of noise reduction than for vibration reduction. However, for frequencies close above the band-gap, the acoustic performance became worse, owing to the increase in acoustic radiation efficiency. Fortunately, the increased sound radiation above the band-gap can be reduced by adding a small damping to the resonator, which further broadens the attenuation frequency band. The reason for the variation of acoustic radiation efficiency is also studied and can be physically explained by the effective mass of an LR unit, where increased mass corresponds to decreased radiation efficiency and decreased mass corresponds to increased radiation efficiency. Thus, the effective mass can be a useful parameter for designers to estimate which frequency component will be acoustically reduced or acoustically enhanced in a practical design.

Effect of In-Plane Forces on Sound Radiation From Convected, Fluid Loaded Plates

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
Peter L. Schmidt ◽  
Kenneth D. Frampton
Keyword(s):  
Acoustic Radiation ◽  
Sound Radiation ◽  
Radiation Efficiency ◽  
Theoretical Development ◽  
Sound Power ◽  
Flow Speeds ◽  
Modes Of Vibration ◽  
Radiated Sound ◽  
Sound Radiation Efficiency ◽  
Power Radiation

The purpose of this work is to study the effects that plane stress has on the acoustic radiation from structures subjected to convected fluid loading. It is well established that fluid flow can have significant effects on structural acoustic behavior, along with the fact that induced coupling between discrete modes of vibration becomes significant as flow velocity increases. Work in this area has been confined to flows in air, over unloaded structures, with the effects on sound radiation efficiency, kinetic energy, and sound power radiation quantified and compared for various flow speeds. Theoretical development of the equations governing the vibration of a simply-supported plate subjected to in-plane forces in an infinite baffle and a semi-infinite flowing medium is presented along with a method for coupling these systems. Computational results are presented illustrating the effect of coupling on the sound power radiated from the plate in both subsonic and supersonic flows, for a variety of stress loading cases. It is shown that the state of stress in the plate affects the radiation efficiency of the plate, and that increasing stress eliminates a frequency shift in radiated sound power shown to exist for both subsonic and supersonic flow in previous work.

Vibration and acoustic radiation of an orthotropic composite cylindrical shell in a hygroscopic environment

2016 ◽  
Vol 23 (4) ◽  
pp. 673-692 ◽  
Author(s):  
Xin Zhao ◽  
Bo Zhang ◽  
Yueming Li
Keyword(s):  
Cylindrical Shell ◽  
Moisture Content ◽  
Acoustic Radiation ◽  
Radiation Power ◽  
Orthotropic Cylindrical Shell ◽  
Sound Radiation ◽  
Composite Cylindrical Shell ◽  
Buckling Mode ◽  
Concentrated Force ◽  
Orthotropic Composite

An analytical study is presented for vibration and acoustic radiation of a finite thin orthotropic composite cylindrical shell excited by a harmonic concentrated force in a hygroscopic environment. The modal analysis method is used to solve the governing equations. Theoretical results are presented in natural vibration, radial quadratic velocity, sound power and radiation efficiency, with uniform incremental moisture content. Furthermore, different stiffness, length and thickness are set respectively to research the effects of the material and structure parameters variation of the orthotropic cylindrical shell on the vibration and acoustic radiation characteristics. It is found that the natural frequencies decrease with an increase of moisture content. The modal indices associated with the lowest frequency mode reaches the modal indices corresponding to the lowest buckling mode near the critical buckling moisture content with moisture content. The radial quadratic velocity and sound radiation power decrease with the incremental moisture content in the lower frequency band. The vibration and acoustic response decrease with the enhanced stiffness. The increasing length has little impact on the sound radiation and the thickened cylindrical shell weakens the sound radiation response.

A MODAL METHOD FOR COUPLED FLUID-STRUCTURE INTERACTION ANALYSIS

2004 ◽  
Vol 12 (02) ◽  
pp. 217-231 ◽  
Author(s):  
SHENG LI ◽  
DEYOU ZHAO
Keyword(s):  
Sound Radiation ◽  
Mode Shapes ◽  
Sound Power ◽  
Stiffened Plate ◽  
Modal Interaction ◽  
Fluid Structure ◽  
Structure System ◽  
Radiated Power ◽  
Vibration And Sound Radiation ◽  
Modal Method

A modal method is developed for solving, analyzing, and controlling vibration and sound radiation of coupled fluid-structure systems. The method recasts the coupled equation of a coupled fluid-structure system in the classical matrix structural dynamic equation by modeling the acoustic load vector as direct linear function of the acceleration, velocity, and displacement vector. With the Rayleigh damping assumption of the coupled fluid-structure system the resulting equation can be uncoupled via a transformation to modal coordinates and analyzed by solving independent equations of single degree of freedom system. The modal radiation efficiencies, effect of modal interaction on sound radiation, mode shapes, and modal control of the coupled fluid-structure system are presented and discussed. Numerical example of the vibration and sound radiation of a fluid-loaded stiffened plate is presented solely as a vehicle to demonstrate the method. The comparisons in terms of computed sound power of the present method with the standard coupling method and available published results show a very good agreement. The mode shapes and the self- and mutual-radiation efficiencies of modes of the fluid-loaded stiffened plate are given and discussed. The study of the effect of modal interaction on sound power shows that the power radiated by a single mode is to increase total radiated power and the interaction of modes may lead to an increase or a decrease or no change in the total radiated power. Numerical results also show that the modal control achieves good reductions in the mean square velocity and the sound power of the fluid-loaded stiffened plate.

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