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Published Articles

The Volume 15, No 2, June 2010

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1-D Acoustical Analysis of Axial-Inlet, Transverse-Outlet Air Cleaners of Rectangular and Circular Cross-Section

M. L. Munjal and N. K. Mukherjee


This paper deals with the prediction of the acoustical performance of two basic types of air cleaners: 1) rectangular axial-inlet transverse-outlet (RAITO) and 2) circular axial-inlet transverse-outlet (CAITO), through 1-D acoustical analysis. Predictions of the acoustical performance of the air cleaners have been validated with 3-D FEM results. The acoustical performance of the cleaner box has been compared with the bare plenum performance (without any filter element) in order to estimate the acoustical performance of the filter element. It has been shown that even if inlet and outlet pipes do not lie exactly on the centre of the corresponding cross section, the 1-D formulation still can predict the transmission loos (TL) with reasonable accuracy in the low- and mid-frequency zones. The 1-D model presented here is not only more convenient and much faster than the 3-D model, and it has the additional advantage of being able to incorporate the effect of mean flow, particularly the dissipative effect of mean flow at the inlet/outlet of the air cleaner. This 1-D model would facilitate a rational design of an air cleaner for control of the intake noise of internal-combustion engines.

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Control of Vibration of Transmission Lines

Marcel Migdalovici, Tudor Sireteanu and Emil M. Videa


The problem of vibration control of overhead line conductors subjected to laminar transverse wind, which induces stationary vibrations by K´arm´an effect, is important due to the consequences on these structures lifetime and ser- vice. We consider the conductor (cable) model as the Euler-Bernoulli beam, fulfilling the authors? condition that detaches the conductor model of the beam model with viscous, hysteretic, or dry friction internal-damping hypoth- esis. The aeolian vibration control of the conductor is based on the energy-balance principle that takes accounts for the wind-energy input, the energy dissipated by the conductor due to hysteretic self-damping properties (or equivalent viscous damping) and, eventually, the energy dissipated by the Stockbridge dampers. The aim of this approach is to mitigate the vibration level of overhead line conductors. The original analytical expression of the free-vibration modes and the resonance-frequencies equation for the cable with clamped extremities have been produced. The analytical expression of the kinetic energy of the cable is compared with the amount of dissipated energy, obtained by experimental means, for the control of vibration of transmission lines. Some applications are presented here.

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Simulation Modeling of Thermoacoustic Cooling and Refrigeration

Abdullah A. Alshorman


Conventional refrigeration requires comprehensive power, control, and maintenance systems, all at high costs.
As a result it is promising to have an alternative method, which is capable of creating cryogenic refrigeration with no moving parts, a clean energy source, and with a relatively simple design and cheap components. This could be achieved through thermoacoustic cooling techniques, which is based on the oscillation of sound waves to circulate heat between high and low heat exchangers within a well-designed thermoacoustic device.
In this study an inclusive acoustic model has been proposed, in which the main parameters have been determined to build up a matrix of constituted engineering-mathematical equations that form the main structure of the modelling process. This modelling has coupled with its associated thermodynamical parameters to form the appropriate thermoacoustic model, which allows for the scaling of parameters, determination of performance rate, and enables refrigeration-performance enhancement.
Our results show that the model can provide a precise margin of applications for each parameter of thermoacoustic refrigeration for different working fluids. Also, it is possible to determine the numerical ranges of efficient cooling for absorbed and released heat (qc, qH), maximum-pressure amplitude (Pm) and sound intensity (I), respectively.

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Vibro-Acoustic Damping Simulation of Two Laminated Glass Panels Coupled to Viscothermal Fluid Layer

Ali Akrout, Lotfi Hammami, Chafik Karra, Mabrouk Ben Tahar, Mohamed Haddar


This paper numerically investigates the vibro-acoustic behavior of two thin film-laminated glass panels coupled to a viscothermal fluid layer. For this purpose, the film-laminate finite element model is coupled to the viscothermal fluid model, introducing an original configuration of a laminated double-glazing system. The two-layer laminated panel finite element is developed using Kirchhoff?s plate theory and by taking into account the shear stress of a con- fined ultra-thin film at the skin?s interface. Then, the developed equations of the laminated glass panel are based on the theory that introduces a particular behavior rule for an ultra-thin film, which includes effects of stiffness, without taking into account the film thickness. After that, the dynamic model is established in an appropriate form, including effects of viscosity and thermal conductivity of fluid and taking into account the acousto-elastic cou- pling. Thus, the developed finite element model is defined by a frequency-dependent symmetrical matrix system that is obtained after discretization and minimization of the coupled system energy function. Hence, a modal iter- ative approach is derived in order to determine the eigenmodes and vibro-acoustic responses of the film-laminated double-glazing system. The validation of the acousto-elastic model is accomplished by comparing the coupled system results against data obtained from the literature. Subsequently, several vibro-acoustic indicators, such as film-laminate strain energies and the transmission loss of the coupled system, for a specified design of a laminated double-glazing system excited by uniform pressure are presented and discussed. The numerical results show the importance of both thin film-lamination and viscothermal fluid effects on double-glazing vibro-acoustic perfor- mance.

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