Structural-acoustic Coupling Research Articles

Study on the deformation of inter-rib shell plate of reinforced conical shell structure under deep-water-explosion loading

The reinforced cylindrical and conical column structures are widely used structural forms in underwater vehicle structures. In this paper, the reinforced conical shell structure in the transition compartment of underwater vehicles was used as the research object. Based on the shock wave propagation theory and ABAQUS acoustic structure coupling numerical simulation method, the numerical simulation model of conical shell structure under deep-water explosion load was established.The deep-water explosion simulation of conical shell structure under the conditions of different water depths, charges and explosion distances was carried out, and the deformation and failure mode of small depressions in the shell plate between ribs of stiffened conical shell structure was obtained, that was, independent small pits were formed along the axis direction. According to the theory of elastic-plastic deformation of plate and shell structure, the small pits of shell and plate between ribs were approximated as the deformation of trapezoidal plate, and the deformation function of trapezoidal plate was obtained by coordinate transformation. The deformation energy of plate and shell was divided into bending deformation energy and midplane strain energy. By establishing the correlation between explosion energy and deformation energy, the theoretical calculation model of the small pit deformation mode of shell and plate between ribs was obtained.

Analysis of the influencing factors of the acoustic performance of the muffler considering acoustic structural coupling

Analysis of the influencing factors of the acoustic performance of the muffler considering acoustic structural coupling

Study on acoustic characteristics of air pipeline with guide vane and bionic guide vane

In this paper, experiments and numerical simulations have been performed to demonstrate that both the guide vane and bionic guide vane can effectively reduce the aerodynamic noise. Both the hybrid calculation method and the acoustic-structure coupling method are employed to calculate the aerodynamic noise of the air pipeline. The impact of the guide vane positioning on the pipeline velocity field and fluctuating pressure is scrutinized and deliberated. Utilizing principles from bionics technology, the bionic groove structure is applied to the bend guide vane, forming a new bionic guide vane. The results show that the bionic guide vane can improve the flow field distribution and substantially mitigates the aerodynamic noise of the elbow effectively.

Characteristics and factors of mode families of axial turbine runner

Axial turbines are widely used in hydropower systems. Owing to the complex hydraulic excitation force during operation, its flow-passing components, particularly the runner, are prone to severe vibrations. To further understand the vibration of the runner under different excitation forces, this study systematically investigated the modal characteristics of an axial turbine runner through numerical simulation using the example of a prototype Kaplan runner, including a shaft. The finite element method (FEM) and acoustic-structure coupling method were used to solve the natural modes of the runner in vacuum and the added mass effect of water, respectively. It was found that the modes of cantilever-blade structures without a shaft are mainly represented as vibrations of the blades, which can be classified into a series of mode families based on the single-blade modes, corresponding to a series of frequency bands with very small widths. The composition of members in each mode family depended strictly on the number of blades with a clear rule. For axial turbines, the modal vibration of the shaft and blades is prone to coupling, which leads to abnormal changes in some modes in the mode family, resulting in the scattering of the natural frequencies and greatly improving the possibility of resonance. The law of mode coupling was revealed, and the effects of the blade opening and bearing stiffness on the mode coupling and frequency bandwidth were explored. The stiffness of the bearing close to the runner significantly affected the frequency bandwidths. The greater the stiffness, the smaller are the bandwidths. This study can provide a reference for resonance cause analysis and vibration avoidance design of axial turbines and similar structures.

Sound transmission of active elastic wave metamaterial with double locally resonant substructures surrounded by external mean flow

The elastic wave metamaterial with active feedback control is presented to discuss its dynamic effective parameter and sound transmission properties. Both studies are initiated from the local resonance with the active feedback control and dynamic structural response. The acoustic-structure coupling of the metamaterial with resonators and orthogonal stiffeners are analyzed with effects of the external mean flow. Different analytical methods are used to derive the effective mass density and sound transmission loss (STL) of the elastic wave metamaterial. The effective density is obtained by the dynamic effective medium method firstly. And the second one applies the spatial harmonic expansion method with the principle of virtual work for the STL based on the Bloch–Floquet theorem and Poisson summations. The effective mass density shows frequency-dependent properties and appears positive and negative values in a certain frequency region simultaneously. This research also illustrates both characteristics can be tuned by the active feedback control with the acceleration and displacement feedback control actions. Numerical results of coupled structures show that the changes of transmission characteristics in the certain frequency region are consistent with the effective mass density properties of uncoupled unit cell structure. In addition, influences of the lattice constants, incident angles and Mach number on the STL are illustrated and discussed.

Prediction of Vibration-Mode-Induced Noise of Structure–Acoustic Coupled Systems

The exposure of a structure to an acoustic domain induces a sound field owing to the interaction of the air-fluid and structure at the acoustic–structure boundaries. It is difficult to predict sound pressure level through vibration mode, due to the acoustic mode of the coupling effect between vibration and sound in addition to the acoustic mode induced by vibration mode generated by external force. In this study, the acoustic mode induced by structural vibration modes were predicted through a numerical analysis. A finite element model of a reverberation chamber with a shell at one side was constructed, and modal parameters of the vibration and acoustic modes were evaluated through an eigenvalue analysis. In addition, the sound pressure generated by impact loading of the shell were predicted by vibration mode through a time-domain structure–acoustic coupling analysis. The vibration and acoustic modal responses were identified from the measured responses, and the acoustic mode associated with a specific vibration mode was examined. The results showed that the acoustic mode from the coupling effect was verified, and sound pressure prediction from vibration mode was possible if considered as the coupling effect. The proposed approach can be applied to predict the heavy-weight floor impact sound from the vibration of slabs in apartments.

A new method for location of the main contribution modes by the decomposed sound pressure

The control of loud structure-borne noise inside car cabins is commonly by analyses such as panel acoustic contribution analysis, sensitivity analysis, and optimization analysis, to find suitable and practical structural modifications. However, these analyses are usually repeated dozens of times before accessing effective structural modifications, which requires more computation and time. This paper presents a new way to decompose sound pressure and quickly locate structural and acoustic modes of the main contribution for efficient access of feasible structural modifications. The decomposition process of the sound pressure inside structure-acoustic coupled systems was summarized by analyzing specific mathematical formulas. The details for locating the structural and acoustic modes of the main contribution by the decomposed sound pressure were investigated, taking a typical structure-acoustic coupled system of a rigid box with one flexible wall at bottom as an example. To evaluate the correctness of the main contribution modes, modifications were suggested in the structural modes of the main contribution, based on the mechanics of structure-acoustic coupling. The results indicated that the interior sound pressures of structure-acoustic coupled systems are decomposed into matrices by certain mathematical formulas. The main contribution modes are located by analyzing larger data in the decomposition matrices. The modifications in the structural modes of the main contribution reduce the corresponding sound pressure, which shows the correctness of the main contribution modes found. Furthermore, one way for quick suggestion of effective structural modifications was proposed, which offers a potential option for the reduction of structure-borne noise inside car cabins.

Vibration cause analysis and elimination of stagnant branch pipeline

Fluid acoustic structure coupling vibration is rare in nuclear power plant (NPP), especially in the stagnant branch of reactor coolant loop (RCL). This paper reports the phenomenon of fluid acoustic solid coupling vibration of one stagnant branch pipeline founding in the hot function test (HFT) of NPP. Field measurement shows that the vibration exceeds the limit value so it is necessary to determine the root cause of pipeline vibration and provide the modified layout. Based on the data of single point measurement, on-line monitoring, knocking test, acoustic modal calculation and modal analysis, the authors obtain the vibration characteristics and laws of pipelines and infers the acoustic solid coupling. The computational fluid dynamics (CFD) analysis and Strouhal number calculation, the inference of fluid acoustic coupling is identified. According to the above inference, the modified layout and the vibration prediction of the modified layout are proposed. After modification the HFT and the power up test was started. The vibration trend was consistent with the prediction, which verified that the fluid acoustic structure coupling was the root cause of the stagnant branch vibration. The amplitude of the modified the stagnant branch pipeline reduced in the whole process of temperature rise. The operation meets the limit requirements. The stagnant branch can operate normally.

Reconfigurable Acoustic Absorber Comprising Flexible Tubular Resonators for Broadband Sound Absorption

Typical acoustic metamaterial absorbers rely on relatively rigid materials for acoustic resonances, which, however, poses a challenge in reshaping and reconfiguring them. Here, we demonstrate soft reconfigurable acoustic absorbers, which are realized by the use of flexible tubular resonators. Owing to the structural compliance, the tube absorbers promote intriguing acoustic-structure coupling and exhibit hybrid resonances of acoustic and structural modes, which are characterized by Rabi splitting in the strong-coupling regime and Fano-like resonance in the weak-coupling regime. Also, the soft walls of the flexible resonators induce decreased resonance frequencies for low-frequency absorption by reducing the effective sound speed inside the tube. Moreover, we find that these hybrid resonances are critically influenced by the structural loss of the flexible resonators. While elucidating the role of the material rigidity and structural loss in acoustic resonances, this work allows us to design versatile broadband absorbers that can be reconfigured depending on the topology of a target substrate.

Case study: Analysis of acoustic-structure coupling noise characteristics of the exhaust muffler of an internal combustion engine

Exhaust noise produced by internal combustion engines is one of the main problems of vehicle noise, and exhaust mufflers can significantly improve this problem. In fact, the sound waves inside the exhaust muffler will cause the muffler shell to vibrate, causing the muffler to produce shell radiation noise. Therefore, it is necessary to carry out the acoustic-structure coupling analysis of the muffler. This paper improved the design of a prototype straight-through perforated pipe-resistant muffler (design A) and designed a straight-through perforated pipe-resistant muffler with a corrugated lining (design B). Structural modal analysis, acoustic modal analysis, and transmission loss analysis of the two mufflers were carried out. The coupling of the acoustic cavity and structure was considered, and the radiation noise of two kinds of resistant mufflers was comparatively analyzed by the direct-boundary-element method. The acoustic radiation of two kinds of resistant mufflers was studied. The pressure loss of the two kinds of mufflers was studied by aerodynamic analysis. The results suggested that the design B muffler effectively improved the noise reduction performance of the prototype muffler, reduced the vibration displacement amplitude of the shell, and reduced the sound power level of the design A muffler.

Modal-interaction approach to the strong structural–acoustic coupling of an elastic Helmholtz resonator and an acoustic cavity containing a heavy fluid

This paper focuses on the development of a method for the accurate representation of the strong structural–acoustic coupling between an elastic Helmholtz resonator, a heavy fluid and an impedance tube. The Helmholtz resonator has an elastic wall and is connected to the impedance tube, yielding a system with two acoustic cavities coupled through a neck and the fluid–structure interaction between a liquid medium and a plate. The proposed analytical formulation is based on the modal superposition method in combination with a lumped parameter model of the neck. The effect of the evanescent waves is taken into account in the form of both the inertial attached length of the neck and the terms of the evanescent pressure modes in the governing equations, which are omitted in other methods. The formulation of the evanescent pressure field is redefined to include the reflected waves, thus expanding the application to the acoustic cavity of an arbitrary shape. Strong coupling between the heavy fluid and the plate is accomplished with the implementation of the non-resonant acoustic modes. Furthermore, the improved performance of the model for moderately thick plates is achieved with the combined approach of the Mindlin–Reissner theory mode shapes and the Kirchhoff–Love theory governing equations. The proposed model is validated with FEA simulations of three different resonator configurations and compared to other applicable methods. The results demonstrate substantially increased accuracy in the predicted response of the coupled structural–acoustic system.

Dynamics analysis of high-speed water entry of axisymmetric body using fluid-structure-acoustic coupling method

The high-speed water entry problem of a rotating body has instantaneous and strong nonlinear characteristics. In order to study the unsteady evolution of the multiphase flow field entering the water and the coupling effect of multiple media and analyze the influence of the noise of different structures, the fluid–structure-acoustic coupling method is used to analyze the numerical simulations of high-speed vertical water entry with different structures are carried out. In this article, we use different materials and structural forms of rigid cylinder, elastic cylinder and concave-head cylinder to analyze the unsteady evolution of the flow field during the water entering process, the dynamic response of the structure and the water flow noise. Through the comparison and analysis of different materials and structural forms, it can be found that the impact load of the rigid cylinder to the water has increased significantly and appeared earlier, the diameter of the cavity contour of the rigid cylinder is small, and the cavity and contraction of the tail of the concave-head cylinder faster. At the same time, the stress distribution of the elastic cylinder and the bottom of the concave-head cylinder is annular, and expands outward along the bottom center, and the stress transmission of the side surface of the concave-head cylinder is faster. Finally, the overall sound pressure level (OSPL) of the three different structures inflow noise at different distances in the four azimuths has basically the same change, and shows a ”saddle-shaped” trend. The research results in this paper can provide a certain reference for the study of multiphase flow field evolution, structural dynamic response characteristics and noise characteristics of high-speed entering water.

Vibro-acoustic characteristics analysis of the rotary composite plate and conical–cylindrical double cavities coupled system

PurposeThe purpose of the study is to obtain and analyze vibro-acoustic characteristics.Design/methodology/approachA unified analysis model for the rotary composite laminated plate and conical–cylindrical double cavities coupled system is established. The related parameters of the unified model are determined by isoparametric transformation. The modified Fourier series are applied to construct the admissible displacement function and the sound pressure tolerance function of the coupled systems. The energy functional of the structure domain and acoustic field domain is established, respectively, and the structure–acoustic coupling potential energy is introduced to obtain the energy functional. Rayleigh–Ritz method was used to solve the energy functional.FindingsThe displacement and sound pressure response of the coupled systems are acquired by introducing the internal point sound source excitation, and the influence of relevant parameters of the coupled systems is researched. Through research, it is found that the impedance wall can reduce the amplitude of the sound pressure response and suppress the resonance of the coupled systems. Besides, the composite laminated plate has a good noise reduction effect.Originality/valueThis study can provide the theoretical guidance for vibration and noise reduction.

Numerical simulation of structure design of magnetoelectric composite ultrasonic levitation device based on multi-physical field coupling

Aiming at the coupling simulation problem that ignores the acoustic structure boundary in the traditional acoustic suspension simulation, based on the magnetostrictive effect, the piezoelectric effect, and the acoustic-structure coupling model, this paper uses a magnetoelectric structure composed of the magnetostrictive material Terfenol-D and the piezoelectric ceramic PZT-5H. The composite material is used as, and the magneto-electric-acoustic fully coupled model of the magneto-electric composite material is established and compared with the one-way coupling model; The particle levitation of magnetoelectric composite materials in the multi-field coupling environment of the magnetic field, electric field, sound field, and displacement field was simulated and calculated; the influence of different widths of magneto-electric composite materials and the size of the resonant cavity on the effect of acoustic levitation was analyzed, and the best results were obtained. The geometric parameters required for optimal suspension are analyzed; the sound pressure output performance of the overall magnetoelectric composite ultrasonic suspension device under the optimal size and the judgment of the suspension position is analyzed, and I displayed the good suspension of the simulated particles in the sound field visually. The research results show that the difference in the amplitude output of the transducer will affect the sound pressure output performance of the transducer, and there is a large error in the one-way coupling; the magnetoelectric composite material can be used as an ultrasonic transducer to achieve acoustic suspension, and suspended particles It shows a good acoustic levitation effect in the simulation. The fully coupled simulation of ultrasonic transducers and the research on such ultrasonic transducers can open new ideas for the research and development of new ultrasonic transducers in the future.

Analysis of ultrasonic partial discharge characteristics of GIS’s reducing unit based on Finite Element Method

GIS’s reducing unit is a new and environment-friendly structural unit, which can greatly reduce the consumption of aluminum alloy material and insulating gas. The structural size of this unit is much smaller than the conventional one. In this paper, an acoustic-structure coupling interaction model of partial discharge in reducing unit of gas insulated switchgear (GIS) is presented. The interaction between the internal acoustic source of partial discharge and structure of GIS is simulated with the finite element analysis, and the acoustic pressure levels distribution of GIS is obtained. The results show that the sound pressure distribution of the reducing unit is basically the same as that of the conventional one, but the amplitude is larger. At the same time, the high-frequency part of the acoustic signal attenuates more quickly in the reducing unit. This paper provides a theoretical guidance basis for the ultrasonic partial discharge detection of the GIS reducing unit.

Sound absorption performance analysis of anechoic coating under hydrostatic pressure considering cavity pressure

Objectives An underwater anechoic coating layer laid on the hull surface of a submarine is squeezed under the action of high hydrostatic pressure, changing its shape and material parameters, which has a great impact on sound absorption performance. Therefore, studying the sound absorption performance of underwater anechoic coating layers under high hydrostatic pressure is of great significance for the stealth performance of submarines. Methods Considering the effects of cavity pressure on deformation and sound absorption performance of the annechoic coating layer under hydrostatic pressure, this paper uses axisymmetric finite element simulation to calculate the deformation of single cell with a cylindrical cavity, and the sound absorption coefficient curve is then obtained by converting the deformations into one-dimensional theoretical model. After that, structural-acoustic coupling analysis with the geometric model after deformation is carried out to verify the effectiveness of theorectical and numerical approaches for soloving the sound absorption coefficient. Results The results indicate that, without considering the changes of material parameters, the unit cells of the layer shrink axially and the cavity shrinks radially under hydrostatic pressure, while the sound absorption curve moves towards high frequency. The air pressure inside the cavity resists contraction under the action of hydrostatic pressure, weakening the trend of moving to high frequency. The sharp valley in the sound absorption curve is caused by the excitation of cavity mode. Conclusions The results of this study can provide valuable references for predicting the sound absorption performance of an anechoic coating layer under hydrostatic pressure.

Vibro-acoustic characteristics of rubber matrix cord-reinforced combined shells of revolution under hydrostatic pressure

The vibro-acoustic characteristics of rubber matrix cord-reinforced combined shells of revolution under hydrostatic pressure are investigated. Under internal pressure of the shell, stress and deformation is generated in the rubber matrix cord-reinforced shell. According to the deformation characteristics of the rope structure under hydrostatic pressure, the axial and circumferential deformation of the shell is discussed. The stress of shell caused by the hydrostatic pressure is considered in the differential equation of motion. Then the transformation relationships of different coordinate systems, and the continuous conditions of state vectors of the shell are established. The transfer matrices for the connection position of the spherical shell and the cylindrical shell, the position of the ring-stiffener are derived. Therefore, the whole vibration transfer equation of the combined shells is assembled. The response of the shell under the excitation force and the generalized sound pressure is calculated separately, and the sound pressure coefficient is solved by the continuous condition at the acoustic-structure coupling boundary. The radiated sound power of the combined shells is obtained. Eventually, the reliability and accuracy of the proposed method is verified by experimental results. Effects of the number of circumferential waves, radius of curvature of spherical shell, the hydrostatic pressure, the ring-stiffeners on the acoustic radiation characteristics of the combined shells are also discussed.

Research on acoustic behaviors of water pipelines with guide vanes

In this paper, the pipeline with guide vanes was taken as the research object, the flow noise was studied based on the hybrid calculation method, then the acoustic-structure coupling method was introduced to study the vibration and radiation noise, and then explored the best position of the guide vanes. Based on the pipeline experimental platform and improved experimental methods, it was found that the guide vanes had a better noise reduction effect on the elbows; based on that, a simulation study was carried out on the elbow with guide vanes, and the mechanism of the guide vanes on the velocity field and pulsating pressure of the pipeline was explored. Finally, the noise reduction effect at different positions of the guide vanes under different flow speeds was studied. The results indicated that the guide vane at the middle of the elbow had the best effect on improving the flow field and reducing noise in the working conditions studied in this article, providing a calculation basis for the design of the guide vane.

구조-음향 연성 시스템의 진동모드에 의한 소음 예측

An acoustic domain combined with a flexible structure induces a unique sound field due to the interaction between a fluid and the structure at acoustic-structure boundaries. In this study, the characteristics of the acoustic modes induced by a structural vibration mode were examined, and the acoustic noise from the vibration mode was predicted using a numerical analysis. For this, a reverberation chamber with a shell at one side was constructed as a finite-element model, and the modal parameters of the vibration and acoustic modes were evaluated using an eigenvalue analysis. In addition, the structural vibration and sound pressure caused by a impulse load impacting the shell were analyzed with a time-domain acoustic-structure coupling analysis, and an acoustic mode was analyzed from a specific vibration mode by identifying the vibration and acoustic modal response from the measured responses. The framework for predicting the acoustic mode presented in this study can enhance the understanding of sound pressure induced by vibration. Further, it is expected that this framework could be applied to predict the heavy weight floor impact sound from the vibration of a slab in an apartment.

Coupled vibro-acoustic analysis of submerged double cylindrical shells with stringers, rings, and annular plates in a symplectic duality system

A wave propagation analysis model of a submerged double cylindrical shell with stringers, rings, and annular plates is established in a symplectic duality system, accounting for acoustic-structure coupling. First, the vibration problem of the double cylindrical shell with stringers is introduced into the symplectic duality system by the Hamiltonian function. The wave propagation parameters and wave shape matrices with symplectic orthogonal relations are obtained by solving a symplectic eigenvalue problem. Then, according to the wave propagation relations, the wave amplitudes are derived by accounting for unknown forces, moments, and pressures induced by the rings, annular plates, and fluid. Finally, the vibration and acoustic responses are obtained through the wave shape matrices and wave amplitudes. In this study, the wave propagation parameters and wave shape matrices are calculated in the symplectic dual space, and the axial thickness discontinuity induced by the rings and annular plates is addressed through the cutting of the wave propagation path. Consequently, the convergence is not affected by the number of rings and annular plates, and the method achieves higher calculation accuracy and efficiency compared with the modal superposition method based on analytical beam functions. The parameter analysis indicates that proper combinations of the number and thickness of the annular plates can significantly reduce the vibro-acoustic responses for the same total mass of the annular plates, while changing the number of rings and stringers cannot. When the inner and outer cylindrical shells lose the same mass, altering the thickness of the outer shell has a greater impact.