The energy reflection coefficient of electrorheological fluid with continuously changing acoustic impedance
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The energy reflection coefficient of electrorheological fluid with continuously changing acoustic impedance Lvhui Ding • Qibai Huang • Zhisheng Xu Qian Zhang
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Received: 29 October 2009 / Accepted: 27 February 2010 / Published online: 20 March 2010 Ó Springer Science+Business Media, B.V. 2010
Abstract The electrorheological fluid (ERF), among the complex fluids, is a kind of smart or intelligent material. At the presence of an external electric field, the dispersed particles in ERF suspensions can form orderly microstructures to a certain extent, resulting in the drastic changes of many physical properties of the materials, such as acoustic impedance. This paper analyzes acoustic attenuation and velocity of acoustic wave in ERF, as a theoretical model the Biot theory has been applied. Then impedance-matching properties of ERF, whose specific acoustic impedance varies smoothly across the ERF, from the effective value of the transducer specific acoustic impedance to the value of the output medium specific acoustic impedance, is analyzed with the transmission matrix method and get the reflection coefficient of ERF. At last, calculate the reflection coefficient of ERF with three impedance profiles. The results show that This impedance
L. Ding (&) Q. Huang Z. Xu Huazhong University of Science and Technology, 430074 Wuhan, People’s Republic of China e-mail: [email protected] Q. Huang e-mail: [email protected] Z. Xu e-mail: [email protected] Q. Zhang China Shipbuilding Industry Corporation, 701 Research Institute, Wuhan, People’s Republic of China
matching technology (IMT) is the most effective for active noise control. Keywords Electrorheological fluid Acoustic impedance Biot theory Acoustic attenuation Transmission matrix Impedance matching technology
1 Introduction Electrorheological fluid (ERF) is made by suspending particles in an insulating liquid whose dielectric constants or conductivity are mismatched so that particles can interact with each other through dipole interactions in the presence of an AC or a DC electric field. If the electric field exceeds a critical value, the transition to a solid state in the ER fluid will occur and the apparent viscosity increases with applied field (Hill and Van Steenkiste 1991). An ERF without an electric field shows nearly Newtonian behavior, but in a electric field the solid particles form chains between the electrodes or, at higher particle concentrations (as shown in Fig. 1). These properties have attracted much attention for their applications in industry and engineering (Nakano and Koyama 1998), many related experimental and theoretical studies have been performed in recent years (Chen et al. 1992; Martin et al. 1998).
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granular medium could be assumed complex and thus modeled the skeletal frame as a viscoelastic solid. This model is often referred as the Biot–Stoll model. In the Biot model of a homogeneous isotropic medium dilatational waves are described by the two differential equations
Fig. 1 View of the parti
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