To reduce the vibration and sound radiation of underwater cylindrical shells,a skin composed of micro floating raft arrays and a compliant wall is proposed in this paper.A vibroacoustic coupling model of a finite cyli...To reduce the vibration and sound radiation of underwater cylindrical shells,a skin composed of micro floating raft arrays and a compliant wall is proposed in this paper.A vibroacoustic coupling model of a finite cylindrical shell covered with this skin for the case of turbulence excitation is established based on the shell theories of Donnell.The model is solved with the modal superposition method to investigate the effects of the structural parameters of micro floating raft elements on the performance of reducing vibration and sound radiation of the cylindrical shell of this skin.The results indicate that increasing the stiffness ratio,damping ratio,mass ratio,or decreasing the interval betweenmicro floating raft elements can improve the vibration and sound radiation reduction performance of this skin over the frequency range 0∼2000 Hz.Moreover,the mean quadratic velocity level and sound radiation power level of the finite cylindrical shell with this skin can be reduced by 12.00 dB and 9.65 dB respectively compared to the finite cylindrical shell with homogeneous viscoelastic coating in the frequency range from0∼2000Hz,implying a favorable performance of this skin for reducing the vibration and sound radiation of cylindrical shells.展开更多
The Donnell theory of shell is applied to describe shell motion and layer motion is described by means of three-dimensional Navier equations.Using deformation harmonious condi- tions of the interface,the effects of st...The Donnell theory of shell is applied to describe shell motion and layer motion is described by means of three-dimensional Navier equations.Using deformation harmonious condi- tions of the interface,the effects of stiffeners and layer are treated as reverse forces and moments acting on the cylindrical shell.In studying the acoustic field produced by vibration of the sub- merged ring-stiffened cylindrical coated shell,the structure dynamic equation,Helmholtz equation in the fluid field and the continuous conditions of the fluid-structure interface compose the cou- pling vibration equation of the sound-fluid-structure.The extract of sound pressure comes down to the extract of coupling vibration equation.By use of the solution of the equation,the influ- ences of hydrostatic pressure,physical characters and geometric parameters of the layer on sound radiation are discussed.展开更多
The research on structural vibration and sound radiation of underwater ring-ribbed cylindrical shell, which is coated with a kind of deadening and decoupling materials, becomes a focus in recent years. This paper anal...The research on structural vibration and sound radiation of underwater ring-ribbed cylindrical shell, which is coated with a kind of deadening and decoupling materials, becomes a focus in recent years. This paper analyzes the problem on two aspects: model experiment and numerical calculation. The model experiment is carried out including three cases firstly, in which the structural vibration response and radiating acoustic field are measured respectively, and the results gained in these three cases are analyzed to discuss the effect of reducing structural vibration and radiating noise of the deadening and decoupling materials. The coupling FEM/BEM and the SEA methods are both used in numerical calculation, i.e. the arithmetic of the coupling FEM/BEM method is adopted to calculate the low frequency characteristics and the SEA method is adopted to calculate the medium-high frequencies characteristics of the model. By comparing experimental results with numerical calculation results, it is proved that the algorithm adopted in this paper is reasonable.展开更多
Based on the motion differential equations of vibration and acoustic coupling system for thin elastic shells with ribs, by means of the Fourier integral transformation and the Fourier inverse transformation, as well a...Based on the motion differential equations of vibration and acoustic coupling system for thin elastic shells with ribs, by means of the Fourier integral transformation and the Fourier inverse transformation, as well as the stationary phase method, an analytic solution, which has satisfying computational effectiveness and precision, is derived for the solution to the vibration and acoustic radiation from a submerged stiffened infinite circular cylinder with both ring and axial ribs. It is easy to analyze the effect of stiffening supports in the acoustic radiation field by use of the formulas obtained by the presented method and corresponding numerical computation. It is shown that the axial-stiffeners can improve the mechanical and acoustical characteristics. Moreover, the present method can be used to study the acoustic radiation mechanism of the type of structure.展开更多
A theoretical model is developed to predict the sound radiation ability of a cylindrical thin elastic shell of finite length, covered with a damp layer and terminated with infinite cylindrical rigid baffles. This shel...A theoretical model is developed to predict the sound radiation ability of a cylindrical thin elastic shell of finite length, covered with a damp layer and terminated with infinite cylindrical rigid baffles. This shell is immersed in a heavy fluid extending up to infinity, and excited by a constant point load continuously traveling along the circumferential direction. A frequency-domain representation of the rotating load and three equations of the vibroacoustic coupling problem are given. The equations are solved by means of modal analysis method and asymptotic expansion method. Also, a mathematical expression of modal amplitude of shell radial displacement is obtained. The sound radiation ability of this kind of shell is evaluated and the corresponding numerical results are given.展开更多
The vibration and sound radiation of a submerged spherical shell are studied in the time-domain by Laplace transform method, where a CW pulse force acts at the apex of the shell. The numerical results for the case of ...The vibration and sound radiation of a submerged spherical shell are studied in the time-domain by Laplace transform method, where a CW pulse force acts at the apex of the shell. The numerical results for the case of long pulse show that the different vibrational modes and the resonant or beat radiated sound are excited for different carrier-frequencies, but litle sound is radiated for some vibrational modes. For the case of short pulse the waveforms of the pulse become widened and deformed, when the pulse propagates between apexes of the shell. Then, the Doubly Asymptotic Approximations (DAA2) and Kirchhoff's Retarded Potential Formulate (KRPF)are used to solve the same problem. It is shown that the results of DAA2 and KRPF method have a good agreement with the results of Laplace transform method.展开更多
A finite element / boundary element-modified modal decomposition method (FBMMD) is presented for predicting the vibration and sound radiation from submerged shell of revolution. Improvement has been made to accelerate...A finite element / boundary element-modified modal decomposition method (FBMMD) is presented for predicting the vibration and sound radiation from submerged shell of revolution. Improvement has been made to accelerate the convergence to FBMD method by means of introducing the residual modes which take into accaunt the quasi -state contributiort of all neglected modes. As an example, the vibration and sound radiation of a submerged spherical shell excited by axisymmetric force are studied in cases of ka=l,2,3 and 4. From the calculated results we see that the FBMMD method shows a significant improvement to the accuracy of surface sound pressure, normal displacement and directivity patterns of radiating sound, especially to the directivity patterns.展开更多
Based on the fundamental dynamic equations of functionally graded material (FGM) cylindrical shell, this paper investigates the sound radiation of vibrational FGM shell in water by mobility method. This model takes in...Based on the fundamental dynamic equations of functionally graded material (FGM) cylindrical shell, this paper investigates the sound radiation of vibrational FGM shell in water by mobility method. This model takes into account the exterior fluid loading due to the sound press radiated by the FGM shell. The FGM cylindrical shell was excited by a harmonic line radial force uniformly distributing along the generator. The FGM shell equations of motion, the Helmholtz equation in the exterior fluid medium and the continuity equation at fluid-shell interface are used in this vibroacoustic problem. The expressions of sound radiation efficiency and sound field of the FGM shell have been derived by mobility method. Radiation efficiency, modal mobility and the directivity pattern of the sound field are solved numerically. In particular, radiation efficiency and directivity pattern with various power law index are analyzed.展开更多
Based on the extended homogeneous capacity high precision integration method and the spectrum method of virtual boundary with a complex radius vector, a novel semi-analytical method, which has satisfactory computation...Based on the extended homogeneous capacity high precision integration method and the spectrum method of virtual boundary with a complex radius vector, a novel semi-analytical method, which has satisfactory computation efectiveness and precision, is presented for solving the acoustic radiation from a submerged infnite non-circular cylindrical shell stifened by longitudinal ribs by means of the Fourier integral transformation and stationary phase method. In this work, besides the normal interacting force, which is commonly adopted by some researchers, the other interacting forces and moments between the longitudinal ribs and the non-circular cylindrical shell are considered at the same time. The efects of the number and the size of the cross-section of longitudinal ribs on the characteristics of acoustic radiation are investigated. Numerical results show that the method proposed is more efcient than the existing mixed FE-BE method.展开更多
The resonance sound radiation from submerged infinite elastic cylindricalshell, excited by internal harmonic line force, is investigated. The shell radiation power ispresented in terms of resonant modal radiation deri...The resonance sound radiation from submerged infinite elastic cylindricalshell, excited by internal harmonic line force, is investigated. The shell radiation power ispresented in terms of resonant modal radiation derived from resonance radiation theory (RRT). Theresonance radiation formulae are derived from classical Rayleigh normal mode solution, which areuseful for understanding the mechanism of sound radiation from submerged shells. As an example,numerical calculation of a thin steel cylindrical shell is done by using these two methods. It seemsthat the results of RRT solutions are in good agreement with that of Rayleigh normal modesolutions.展开更多
In this paper, analytical formularions of radiated sound pressure of ring-stiffenedcylindrical shells in fluid medium are derived by means of Hamilton's principleHuygens principle and Green function . These formul...In this paper, analytical formularions of radiated sound pressure of ring-stiffenedcylindrical shells in fluid medium are derived by means of Hamilton's principleHuygens principle and Green function . These formulations Can be used to compute the sound pressure of the shell's surface nearfield and farfield.展开更多
This work examines the physical effect of the edge-induced acoustic radiation force and torque on an acoustically radiating infinitely-long circular cylindrical source,located near a rigid corner.Assuming harmonic(lin...This work examines the physical effect of the edge-induced acoustic radiation force and torque on an acoustically radiating infinitely-long circular cylindrical source,located near a rigid corner.Assuming harmonic(linear)radiating waves of the source,vibrating in monopole or dipole radiation modes near a rigid corner-space in a non-viscous fluid,the modal series expansion method in cylindrical coordinates,the classical method of images and the translational addition theorem are applied to obtain the mathematical expressions for the radiation force and torque components in exact partial-wave series.Computational results illustrate the theory,and examine some of the conditions where the radiation force and torque components vanish,which has the potential to achieve total motion suppression(i.e.,translation or rotation).Furthermore,depending on the size parameter of the source and the distances from the rigid corner space,these physical observables take positive or negative values,anticipating the prediction of pulling/pushing motions toward the corner space,and possible spinning of the source clockwise or counter-clockwise.The present analysis and its results may be useful in some applications related to underwater acoustical oceanographic engineering of submerged objects,cloaking and stealth technology development and the experimental design of elongated unmanned autonomous vehicles or submarines,as well as the manipulation of an active carrier or ultrasound contrast agents of elongated cylindrical shapes near a corner space or chamber walls at a right angle.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.51775123,52075111)the Fundamental Research Funds for the Central Universities(Grant No.3072021CF0702).
文摘To reduce the vibration and sound radiation of underwater cylindrical shells,a skin composed of micro floating raft arrays and a compliant wall is proposed in this paper.A vibroacoustic coupling model of a finite cylindrical shell covered with this skin for the case of turbulence excitation is established based on the shell theories of Donnell.The model is solved with the modal superposition method to investigate the effects of the structural parameters of micro floating raft elements on the performance of reducing vibration and sound radiation of the cylindrical shell of this skin.The results indicate that increasing the stiffness ratio,damping ratio,mass ratio,or decreasing the interval betweenmicro floating raft elements can improve the vibration and sound radiation reduction performance of this skin over the frequency range 0∼2000 Hz.Moreover,the mean quadratic velocity level and sound radiation power level of the finite cylindrical shell with this skin can be reduced by 12.00 dB and 9.65 dB respectively compared to the finite cylindrical shell with homogeneous viscoelastic coating in the frequency range from0∼2000Hz,implying a favorable performance of this skin for reducing the vibration and sound radiation of cylindrical shells.
基金Project supported by the National Defence Science and Technology Emphases Laboratory Foundation of China(No.99JS23.2.1.JWO506).
文摘The Donnell theory of shell is applied to describe shell motion and layer motion is described by means of three-dimensional Navier equations.Using deformation harmonious condi- tions of the interface,the effects of stiffeners and layer are treated as reverse forces and moments acting on the cylindrical shell.In studying the acoustic field produced by vibration of the sub- merged ring-stiffened cylindrical coated shell,the structure dynamic equation,Helmholtz equation in the fluid field and the continuous conditions of the fluid-structure interface compose the cou- pling vibration equation of the sound-fluid-structure.The extract of sound pressure comes down to the extract of coupling vibration equation.By use of the solution of the equation,the influ- ences of hydrostatic pressure,physical characters and geometric parameters of the layer on sound radiation are discussed.
文摘The research on structural vibration and sound radiation of underwater ring-ribbed cylindrical shell, which is coated with a kind of deadening and decoupling materials, becomes a focus in recent years. This paper analyzes the problem on two aspects: model experiment and numerical calculation. The model experiment is carried out including three cases firstly, in which the structural vibration response and radiating acoustic field are measured respectively, and the results gained in these three cases are analyzed to discuss the effect of reducing structural vibration and radiating noise of the deadening and decoupling materials. The coupling FEM/BEM and the SEA methods are both used in numerical calculation, i.e. the arithmetic of the coupling FEM/BEM method is adopted to calculate the low frequency characteristics and the SEA method is adopted to calculate the medium-high frequencies characteristics of the model. By comparing experimental results with numerical calculation results, it is proved that the algorithm adopted in this paper is reasonable.
基金This work was financially supported by the National Natural Science Foundation of China(Grant No.10172038)
文摘Based on the motion differential equations of vibration and acoustic coupling system for thin elastic shells with ribs, by means of the Fourier integral transformation and the Fourier inverse transformation, as well as the stationary phase method, an analytic solution, which has satisfying computational effectiveness and precision, is derived for the solution to the vibration and acoustic radiation from a submerged stiffened infinite circular cylinder with both ring and axial ribs. It is easy to analyze the effect of stiffening supports in the acoustic radiation field by use of the formulas obtained by the presented method and corresponding numerical computation. It is shown that the axial-stiffeners can improve the mechanical and acoustical characteristics. Moreover, the present method can be used to study the acoustic radiation mechanism of the type of structure.
文摘A theoretical model is developed to predict the sound radiation ability of a cylindrical thin elastic shell of finite length, covered with a damp layer and terminated with infinite cylindrical rigid baffles. This shell is immersed in a heavy fluid extending up to infinity, and excited by a constant point load continuously traveling along the circumferential direction. A frequency-domain representation of the rotating load and three equations of the vibroacoustic coupling problem are given. The equations are solved by means of modal analysis method and asymptotic expansion method. Also, a mathematical expression of modal amplitude of shell radial displacement is obtained. The sound radiation ability of this kind of shell is evaluated and the corresponding numerical results are given.
文摘The vibration and sound radiation of a submerged spherical shell are studied in the time-domain by Laplace transform method, where a CW pulse force acts at the apex of the shell. The numerical results for the case of long pulse show that the different vibrational modes and the resonant or beat radiated sound are excited for different carrier-frequencies, but litle sound is radiated for some vibrational modes. For the case of short pulse the waveforms of the pulse become widened and deformed, when the pulse propagates between apexes of the shell. Then, the Doubly Asymptotic Approximations (DAA2) and Kirchhoff's Retarded Potential Formulate (KRPF)are used to solve the same problem. It is shown that the results of DAA2 and KRPF method have a good agreement with the results of Laplace transform method.
文摘A finite element / boundary element-modified modal decomposition method (FBMMD) is presented for predicting the vibration and sound radiation from submerged shell of revolution. Improvement has been made to accelerate the convergence to FBMD method by means of introducing the residual modes which take into accaunt the quasi -state contributiort of all neglected modes. As an example, the vibration and sound radiation of a submerged spherical shell excited by axisymmetric force are studied in cases of ka=l,2,3 and 4. From the calculated results we see that the FBMMD method shows a significant improvement to the accuracy of surface sound pressure, normal displacement and directivity patterns of radiating sound, especially to the directivity patterns.
基金supported by the Key Project of the National Natural Science Foundation of China (10932006)Hebei Natural Science Foundation (2011210055)Hebei Key Basic Research Project (10963528D)
文摘Based on the fundamental dynamic equations of functionally graded material (FGM) cylindrical shell, this paper investigates the sound radiation of vibrational FGM shell in water by mobility method. This model takes into account the exterior fluid loading due to the sound press radiated by the FGM shell. The FGM cylindrical shell was excited by a harmonic line radial force uniformly distributing along the generator. The FGM shell equations of motion, the Helmholtz equation in the exterior fluid medium and the continuity equation at fluid-shell interface are used in this vibroacoustic problem. The expressions of sound radiation efficiency and sound field of the FGM shell have been derived by mobility method. Radiation efficiency, modal mobility and the directivity pattern of the sound field are solved numerically. In particular, radiation efficiency and directivity pattern with various power law index are analyzed.
基金Project supported by the National Natural Science Foundation of China(No.10172038),the Doctoral Foundation ofthe National Education Ministry(No.20040487013)and the Natural Science Foundation of Guangxi(No.0339019).
文摘Based on the extended homogeneous capacity high precision integration method and the spectrum method of virtual boundary with a complex radius vector, a novel semi-analytical method, which has satisfactory computation efectiveness and precision, is presented for solving the acoustic radiation from a submerged infnite non-circular cylindrical shell stifened by longitudinal ribs by means of the Fourier integral transformation and stationary phase method. In this work, besides the normal interacting force, which is commonly adopted by some researchers, the other interacting forces and moments between the longitudinal ribs and the non-circular cylindrical shell are considered at the same time. The efects of the number and the size of the cross-section of longitudinal ribs on the characteristics of acoustic radiation are investigated. Numerical results show that the method proposed is more efcient than the existing mixed FE-BE method.
基金This project is supported by National Natural Science Foundation of China(No.19974024).
文摘The resonance sound radiation from submerged infinite elastic cylindricalshell, excited by internal harmonic line force, is investigated. The shell radiation power ispresented in terms of resonant modal radiation derived from resonance radiation theory (RRT). Theresonance radiation formulae are derived from classical Rayleigh normal mode solution, which areuseful for understanding the mechanism of sound radiation from submerged shells. As an example,numerical calculation of a thin steel cylindrical shell is done by using these two methods. It seemsthat the results of RRT solutions are in good agreement with that of Rayleigh normal modesolutions.
文摘In this paper, analytical formularions of radiated sound pressure of ring-stiffenedcylindrical shells in fluid medium are derived by means of Hamilton's principleHuygens principle and Green function . These formulations Can be used to compute the sound pressure of the shell's surface nearfield and farfield.
基金Foundation item: Supported by the National Natural Science Foundation of China under Grant No. 11274080, and the Young Scientists Fund of the National Natural Science Foundation of China under Grant No. 11404313.
文摘This work examines the physical effect of the edge-induced acoustic radiation force and torque on an acoustically radiating infinitely-long circular cylindrical source,located near a rigid corner.Assuming harmonic(linear)radiating waves of the source,vibrating in monopole or dipole radiation modes near a rigid corner-space in a non-viscous fluid,the modal series expansion method in cylindrical coordinates,the classical method of images and the translational addition theorem are applied to obtain the mathematical expressions for the radiation force and torque components in exact partial-wave series.Computational results illustrate the theory,and examine some of the conditions where the radiation force and torque components vanish,which has the potential to achieve total motion suppression(i.e.,translation or rotation).Furthermore,depending on the size parameter of the source and the distances from the rigid corner space,these physical observables take positive or negative values,anticipating the prediction of pulling/pushing motions toward the corner space,and possible spinning of the source clockwise or counter-clockwise.The present analysis and its results may be useful in some applications related to underwater acoustical oceanographic engineering of submerged objects,cloaking and stealth technology development and the experimental design of elongated unmanned autonomous vehicles or submarines,as well as the manipulation of an active carrier or ultrasound contrast agents of elongated cylindrical shapes near a corner space or chamber walls at a right angle.