Acoustic Velocity and Attenuation in Magnetorhelogical fluids based on an effective density fluid model

Min Shen,Qibai Huang,H Gong,J.H Lee,B Yan

doi:10.1051/matecconf/20164501001

Abstract

Magnetrohelogical fluids (MRFs) represent a class of smart materials whose rheological properties change in response to the magnetic field, which resulting in the drastic change of the acoustic impedance. This paper presents an acoustic propagation model that approximates a fluid-saturated porous medium as a fluid with a bulk modulus and effective density (EDFM) to study the acoustic propagation in the MRF materials under magnetic field. The effective density fluid model derived from the Biot’s theory. Some minor changes to the theory had to be applied, modeling both fluid-like and solid-like state of the MRF material. The attenuation and velocity variation of the MRF are numerical calculated. The calculated results show that for the MRF material the attenuation and velocity predicted with this effective density fluid model are close agreement with the previous predictions by Biot’s theory. We demonstrate that for the MRF material acoustic prediction the effective density fluid model is an accurate alternative to full Biot’s theory and is much simpler to implement.

Highlights

Magnetorheological fluids (MRFs) are materials whose properties change when an external electro-magnetic field is applied
MRFs material can be used in design of active sound barriers to control noise transmission loss and for modification of noise absorption characteristics of sound absorbing materials [1]
If the magnetic field is removed, the suspension turns to a Newtonian fluid and the transition between these two phases is highly reversible, which provides a unique feature of electric- or magnetic-field controllability of acoustic impedance of MRF

Summary

Introduction

Magnetorheological fluids (MRFs) are materials whose properties change when an external electro-magnetic field is applied. If the magnetic field is removed, the suspension turns to a Newtonian fluid and the transition between these two phases is highly reversible, which provides a unique feature of electric- or magnetic-field controllability of acoustic impedance of MRF. This feature has inspired the design of new active sound barriers to control noise transmission loss or as acoustic metamaterials with negative effective dynamic bulk modulus [2,3]. This paper presents an effective density fluid model that studies the acoustic propagation in the MRF material under magnetic field to simple the Biot’s model. The effective density fluid model (EDFM) approximates a fluid-saturated porous medium as a fluid with a bulk modulus and effective density derived from Biot’s theory

The Biot’s model

The effetive density fluid model

Numerical Results and Discussion