A Parametric Analysis on the Sound Absorbing Performance of the Locally Resonant Sonic Material Using a Mass-Damper-Spring Model
Bo Yuan,
Min Jiang,
Miao He,
Shuai Tang,
Li Zhang,
Minglin Tu
Issue:
Volume 4, Issue 5, September 2016
Pages:
124-133
Received:
11 July 2016
Accepted:
20 July 2016
Published:
3 August 2016
Abstract: The locally resonant sonic material (LRSM) is a kind of structural composite. Such composite typically consists of an elastic matrix periodically embedded with metallic spheres, which are coated with soft rubber. Owing to its capability of controlling the low frequency sound, the LRSM has a promising prospect in the application of underwater acoustic materials. This paper proposes a mass-damper-spring model to explain the sound absorbing mechanism of the LRSM, and derives analytical formulae to evaluate the absorbing performance. After reasonable simplification, the analytical formulae can intuitively illustrate the relationship between the absorbing performance and the parameters of the LRSM. The correctness of the physical model was verified by comparing the analytical evaluation with the numerical result calculated by the layer-multiple-scattering method. The result shows that the sound absorption of the LRSM is induced by the energy dissipation of the damped local resonator subjected to excitations. The influence of the parameters on the absorbing performance of the LRSM is analysed systematically. It is shown that a resonator with a heavier core and a stiffer coat can produce a better sound absorbing performance.
Abstract: The locally resonant sonic material (LRSM) is a kind of structural composite. Such composite typically consists of an elastic matrix periodically embedded with metallic spheres, which are coated with soft rubber. Owing to its capability of controlling the low frequency sound, the LRSM has a promising prospect in the application of underwater acoust...
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Thermal Performance of Electrocaloric Refrigeration using Thermal Switches of Fluid Motion and Changing Contact Conductance
Shigeki Hirasawa,
Tsuyoshi Kawanami,
Katsuaki Shirai
Issue:
Volume 4, Issue 5, September 2016
Pages:
134-139
Received:
19 September 2016
Published:
19 September 2016
Abstract: Thermal performance of electrocaloric refrigeration system composed with a thin electrocaloric material and thermal switches was numerically calculated. Two types of thermal switches were studied: a thermal switch of fluid motion and a thermal switch by changing the contact thermal conductance. The following results were obtained. For the thermal switch of fluid motion with the frequency 10 Hz, the thicknesses of the electrocaloric material 200 μm and the water flow channel 100 μm, the average heat transfer efficiency was 11%. For the thermal switch by changing contact thermal conductance with the frequency 1000 Hz, the thicknesses of the electrocaloric material 20 μm and the heat storage material 20 μm, the average heat transfer efficiency was 6% and the average heat flux transferred to the cold side of the system was 7 x 104 W/m2.
Abstract: Thermal performance of electrocaloric refrigeration system composed with a thin electrocaloric material and thermal switches was numerically calculated. Two types of thermal switches were studied: a thermal switch of fluid motion and a thermal switch by changing the contact thermal conductance. The following results were obtained. For the thermal s...
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