ISSN:0029-5981    

DOI:10.1002/nme.1620371702

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractSeveral new issues related to the project described in References 1–3 are reported. The presented problems include1sensitivity ofp‐convergence results to geometric parametrizations and an idea of a new mesh generation forhp‐approximations,2a posteriorierror estimation for the coupled problem,3a better understanding of the meaning of the asymptotic convergence.A few typical numerical examples conclude the present

ISSN:0029-5981    

DOI:10.1002/nme.1620371703

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractThe analysis of fluid‐filled thin shells is discussed in this paper. It is well known that a boundary element formulation of the exterior acoustic problem becomes ill‐conditioned at certain critical frequencies. For a coupled boundary‐element/finite element formulation of the coupled elasioacoustic problem the formulation suffers from the same numerical ill‐conditioning. However, for fluid‐filled thin shell problems the resulting coupled formulation is unique at all frequencies. In this paper the condition numbers of the coupled and uncoupled formulations are calculated and the uniqueness of the coupled formulation is demonstrated for submerged fluid‐filled

ISSN:0029-5981    

DOI:10.1002/nme.1620371704

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

ISSN:0029-5981    

DOI:10.1002/nme.1620371705

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractThe propagation and decay of acoustic waves in exterior domains in an essential ingredient in the study of fluid–structure interaction. A strategy must be devised to compute solutions over domains which are unbounded. Exact impedance conditions at an artificial external boundary are specified by the DtN method, yielding an equivalent problem that is suitable for domain‐based computation. The DtN boundary condition is non‐reflective, giving rise to exact (and thereby unique) solutions. The truncated DtN operator, which is employed in practice, fails to inhibit the reflection of higher modes, so that non‐unique solutions may occur at their harmonics. Simple expressions determine a sufficient number of terms in the truncated operator for unique solutions at any given wave number. There are three characteristic length scales in the computational problem: the radius of the artificial boundary, the geometry of the body (represented by the internal boundary) and the mesh size. Numerical studies examine the dependence of the conditioning of finite element coefficient matrices on the number of terms in the truncated DtN operator vs. the wave number non‐dimensionalized by each of the length scales. Analytic results regarding the number of terms sufficient for unique solutions are confirmed. As long as this criterion is respected, no upper limit on the allowable wave number is detected. A local approximation of the boundary conditions restores uniqueness for all wav

ISSN:0029-5981    

DOI:10.1002/nme.1620371706

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractThe problem of axisymmetric shells submerged in an infinite fluid subjected to an arbitrary loading is usually solved by reducing the system to a set of two‐dimensional problems. This is accomplished by using Fourier series, thereby uncoupling the circumferential harmonics of the axisymmetric system. Thus, a computationally expensive three‐dimensional solution is replaced by a computationally efficient set of two‐dimensional solutions without any loss of accuracy. However, with the addition of arbitrary three‐dimensional subsystems internal to the submerged axisymmetric shell, the circumferential harmonics become coupled. In this case, the computational advantage attributable to the circumferential Fourier decomposition compared to a fully three‐dimensional solution is greatly reduced.This paper introduces a novel method to solve such three‐dimensional systems while keeping the circumferential harmonics of the axisymmetric shell uncoupled. This is accomplished by relating the admittance matrix of the three‐dimensional substructure, expressed in terms of its connection degrees of freedom, and the response of the empty system to solve for the interaction forces between the axisymmetric shell and the internal system. Using these interaction forces, the response of the full system can be obtained, Thus, the efficiency of the two‐dimensional solution is maintained while solving an arbitrary three‐dimensional problem. Sample problems illustrating the performance of this approa

ISSN:0029-5981    

DOI:10.1002/nme.1620371707

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractA new method for obtaining the response of a baffled, fluid‐loaded, finite cylindrical shell using the finite element method is presented. The Galerkin finite element formulation for this problem utilizes a Neumann Green's function representation of the pressure loading on the shell. By representing the pressure loading in this manner, only the structure need be discretized. Both

ISSN:0029-5981    

DOI:10.1002/nme.1620371708

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractThe effect of fluid loading on a structure embedded with a periodic distribution of piezoelectric transducers is considered in a hybrid formulation that involves a finite element formulation for the structure and transducers that is coupled to an analytical series representation of the acoustic field in the fluid. The passive fluid loading redefines the stiffness matrix via a radiation impedance term. Modal analysis of the array can be effected for elastic vibrations, open and close circuited electrical boundary conditions. General damping in the stiffness as well as dielectric constants is considered. Sensor and actuator equations are then formulated. The actuator equations permit computation of the displacement and stress distribution in the transducer and structure when a known voltage is applied to the transducer electrodes. The sensor equation is illustrated for the case of a known incident plane harmonic wave obliquely incident on the array. The voltage induced in the transducer elements can then be computed.

ISSN:0029-5981    

DOI:10.1002/nme.1620371709

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractSince Soize introduced the concept of fuzzy structures in structural acoustics there has been little activity clarifying the basic elements which underlie his theory. Soize's papers are not easy reading due to the high level of mathematical formalism. In addition Soize simultaneously bases this fuzzy structure theory on two components: (1) a model for one Degree Of Freedom (DOF) fuzzy oscillators, and (2) a medium frequency solution method developed previously. It is unclear as to the role of the two components, although others have already undertaken a study of the medium frequency method by itself.In the present paper a fundamental analysis of the first component, the one‐DOF fuzzy oscillators, is undertaken. The symbolic manipulation programMathematicais utilized to gain insight into this component of Soize's fuzzy theory. The resultingMathematicasimulations are easy to use and interpret, and they provide valuable insight into the parameters composing Soize's fuzzy oscillators. It is determined that in many cases of structural acoustics, where there is small damping and a medium to high modal density, the fuzzy mass primarily determines what effect a discrete fuzzy oscillator will have as an attachmen

ISSN:0029-5981    

DOI:10.1002/nme.1620371710

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY

ISSN:0029-5981    

DOI:10.1002/nme.1620371711

出版商:John Wiley&Sons, Ltd    

年代:1994

数据来源: WILEY