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In this paper, the vibro-acoustic behaviour of a laminated glass plate composed of two elastic skins, a viscoelastic core and two ultra-thin adhesive films; is investigated. Here, the coupled dynamic model is derived by mixing the classical plate’s theories (Mindlin and Kirchhoff models) and the specific behaviour law for the ultra-thin films, previously introduced in our published works in Applied Acoustics Journal [1], with an integral equation formulation for the acoustic radiation of the studied structure. The discretized coupled dynamic equation associated to the energy functional is solved in order to determine the vibratory and acoustic efficiency of the designed laminate. For this purpose, a numerical validation of the finite element model is achieved by using the calculated results corresponding to a standard sandwich plate. In order to predict the vibro-acoustic responses, a modal recombination method is developed by taking into account the external fluid radiation. Hence, the effects of many parameters on some vibro-acoustic indicators (deflection, strain energy, transmission loss) such as core thickness, geometrical property, modal damping and boundary condition are presented and discussed. Especially, the influence of the ultra-thin adhesive films due to the coupling with the viscoelastic core on both dynamic and vibro-acoustic behaviours of the laminate is presented and analyzed.

This paper deals with a new numerical model for predicting the dynamical behaviour of a laminated plate composed of two glass skins and a viscoelastic core (PVB: butyral polyvinyl) assembled by two adhesive ultra-thin films. In order to introduce the effect of the ultra-thin films, some suggestions are considered in the kinematic hypothesis. Therefore, a new dynamic model is highlighted by mixing Kirchhoff and Mindlin plate’s theories, respectively for the two skins and the core with a specific behaviour law for the adhesive ultra-thin films. Then, the finite element method is used to calculate the elastic eigenmodes which are compared to those corresponding to the experimental study. Besides, a hysteretic structural damping is considered in the viscoelastic core model. Hence, the aim of this work is to characterize the modal damping due to the coupling between the different layers of the complex structure. Thus, a dynamic modal analysis is carried out via both, the calculation of the vibratory responses and the modal recombination method. The influence of some parameters such as; the thickness of the core, the length, the width and the area of laminate on the modal structural plate damping have been investigated in details. Then, numerical results show the importance of the adhesive film shear effects on the modal damping of the studied structure.

A theoretical analysis on transient flow inside a centrifugal pump was carried out, building on unsteady and incompressible fluid equations applied to the impeller during the starting periods. The transient flow behavior is governed by two hyperbolic partial differential equations; namely continuity and motion equations. The characteristics method of the specified time intervals was used to analyze the dynamic characteristic of the pump. To follow the dynamic behavior of the pump during startup periods, a numerical study was performed on the pump impeller with different openings of the discharge valve. The comparison between the numerical and experimental results of the pump characteristic curve has shown a good concordance. The results have also revealed that the pressure increase is important in the case of a short starting period of the pump and a large mass of water in the pipelines. In this study, the effect of the impeller diameter and number of blades on the pressure evolution was also analyzed.

This paper deals with the effect of the temperature and the frequency on the acoustic behavior of lined duct partially treated with usual material used in acoustic insulation. First, the effect of frequencies and temperature on the acoustic impedance of usual materials used in lined duct such as glass or rock wools in order to reduce acoustic level is investigated. Secondly, the variational formulation of the acoustic duct problem taking into account velocity and temperature effects is established. Then, a numerical model is derived which permits to compute the reflection and the transmission coefficients of such duct for different temperatures and several flow velocities. The acoustic power attenuation is then computed from these coefficients and the effect of the temperature and flow velocities on this energetic quantity is evaluated. The numerical results are obtained for three configurations of a lined duct treated for different temperature ranges and several velocities. Numerical coefficients of transmission and reflection as well as the acoustic power attenuation show the relative influence of temperature.

This paper presents a new numerical model to investigate the vibro-acoustic behaviour of two laminated glass plates enclosing a thin viscothermal fluid cavity. The aim of this work is to develop an original five layer (two skins plies, two adhesive films and a core ply) laminated plate finite element by mixing Kirchhoff and Mindlin plate’s theory. The formulation is based on the theory that accounts for the transverse shear in the adhesive films and in the core. The acousto-elastic model is established in dimensionless appropriate form including the effects of viscosity and thermal conductivity of fluid and by taking into account the fluid-structure interaction. The discretization of the energy functional by finite element method gives after minimisation a symmetrical coupled matrix system in which the acoustic matrices are frequency dependent. Therefore, an iterative procedure is derived to determine the eigenmodes of the coupled system. The modal approach is adopted to determine the vibro-acoustic system’s response. Then, the validation of the new laminate finite element model is achieved by comparing the sandwich plate results against data obtained from literature. Subsequently, predicted responses, such as the vibration transmissibility and the transmission loss of the coupled system, for a given laminated double glazing under an imposed homogeneous pressure are presented and discussed. Numerical results show the importance of both lamination and viscothermal fluid effects on double glazing vibro-acoustic behaviour.