Wyniki wyszukiwania - BazTech

1

Active Transient Acousto-Structural Response Control of a Smart Cavity-Coupled Circular Plate System

Hasheminejad S. M., Shakeri R.

Archives of Acoustics

|

2017

|

Vol. 42, No. 2

273--286

EN

The transient vibroacoustic response suppression of a piezo-coupled sandwich circular plate backed by a rigid-walled cylindrical acoustic enclosure is investigated. Problem formulation is based on the linear acoustic wave theory, Kirchhoff thin plate model, fluid/structure compatibility relations, Rayleigh integra formula, and active damping control (ADC) strategy. Matlab’s Genetic Algorithm (GA) is utilized to identify and optimize the feedback controller gain parameter based on a multi-objective performance index function. Durbin’s numerical Laplace inversion scheme is then used to calculate the key acousto-structural response parameters due to a transverse impulsive shock force for selected cavity depths. Numerical simulations demonstrate satisfactory performance of adopted control methodology in effective suppression of panel displacement response and radiated external sound pressure for enclosures of shallow and moderate depths. Limiting cases are considered and accuracy of the proposed model is rigorously verified.

2

Active Transient Sound Radiation Control from a Smart Piezocomposite Hollow Cylinder

Hasheminejad S. M., Rabbani V.

Archives of Acoustics

|

2015

|

Vol. 40, No. 3

359--381

EN

The linear 3D piezoelasticity theory along with active damping control (ADC) strategy are applied for non-stationary vibroacoustic response suppression of a doubly fluid-loaded functionally graded piezolaminated (FGPM) composite hollow cylinder of infinite length under general time-varying excitations. The control gain parameters are identified and tuned using Genetic Algorithm (GA) with a multi-objective performance index that constrains the key elasto-acoustic system parameters and control voltage. The uncontrolled and controlled time response histories due to a pair of equal and opposite impulsive external point loads are calculated by means of Durbin’s numerical inverse Laplace transform algorithm. Numerical simulations demonstrate the superior (good) performance of the GA-optimized distributed active damping control system in effective attenuation of sound pressure transients radiated into the internal (external) acoustic space for two basic control configurations. Also, some interesting features of the transient fluid-structure interaction control problem are illustrated via proper 2D time domain images and animations of the 3D sound field. Limiting cases are considered and accuracy of the formulation is established with the aid of a commercial finite element package as well as comparisons with the current literature.

3

Ultrasonic scattering from compressible cylinders including multiple scattering and thermoviscous effects

Hasheminejad S. M., Alibakhshi M. A.

Archives of Acoustics

|

2006

|

Vol. 31, No. 2

243-263

EN

This paper presents a study of acoustic scattering by a pair of parallel circular thermoviscous fluid cylinders submerged in an unbounded viscous thermally conducting medium. The translational addition theorem for cylindrical wave functions, the appropriate wave field expansions and the pertinent boundary conditions are employed to develop a closed-form solution in the form of infinite series. The analytical results are illustrated with a numerical example in which two identical thermoviscous fluid cylinders are insonified by a nearby parallel acoustic line source at broadside/end-fire incidence. The backscattered pressure amplitude is numerically evaluated and discussed for representative values of the parameters characterizing the system. The effects of source position, transmission frequency and proximity of the two cylinders are examined. Particular attention has been focused on multiple scattering interactions as well as thermoviscous effects. The imperative influence of thermoviscosity on the analysed phenomena is revealed by notable reduction of backscattering amplitude at intermediate and high frequencies. The numerical results also show that the multiple scattering interaction effects are of great (moderate) consequence for end-fire (broadside) incidence at small separations of the cylinders. A limiting case involving a pair of ideal compressible fluid cylinders is considered and a fair agreement with preceding solutions is established.