This study investigates a dual-cavity resonant composite sound-absorbing structure based on a micro-perforated plate.Using the COMSOL impedance tube model,the effects of various structural parameters on sound absorpti...This study investigates a dual-cavity resonant composite sound-absorbing structure based on a micro-perforated plate.Using the COMSOL impedance tube model,the effects of various structural parameters on sound absorption and sound insulation performances are analyzed.Results show that the aperture of the micro-perforated plate has the greatest influence on the sound absorption coefficient;the smaller the aperture,the greater is this coefficient.The thickness of the resonance plate has the most significant influence on the sound insulation and resonance frequency;the greater the thickness,the wider the frequency domain in which sound insulation is obtained.In addition,the effect of filling the structural cavity with porous foam ceramics has been studied,and it has been found that the porosity and thickness of the porous material have a significant effect on the sound absorption coefficient and sound insulation,while the pore size exhibits a limited influence.展开更多
Presence of the outer perforated cylinder reduces the direct wave impact on the inner cylinder, which has been testified by many researchers. However, the force reduction mechanism, which is complicated due to the wav...Presence of the outer perforated cylinder reduces the direct wave impact on the inner cylinder, which has been testified by many researchers. However, the force reduction mechanism, which is complicated due to the wave-porous structure interaction, needs to be addressed in detail. The present study explains the mechanism with the aid of the computational fluid dynamics （CFD） tool STAR CCM＋. This package is chosen for its capabilities to simulate viscous and turbulence effects caused by passage of waves. For the present study, flow fields around the twin cylinders with different orientations are examined with and without the outer perforated cover. Mechanism contributing to the reduction of force on the existing structure is explained in physical terms, and force reduction is quantified. The present study has direct application in the retrofitting application of offshore members.展开更多
Porous structures are highly preferred for bone regeneration and high tissue in-growth.In present work,electrical discharge drilling(EDD),a thermal erosion process was used to produce through holes in Mg-alloys to fab...Porous structures are highly preferred for bone regeneration and high tissue in-growth.In present work,electrical discharge drilling(EDD),a thermal erosion process was used to produce through holes in Mg-alloys to fabricate perforated structure similar to open cell porous structure in extruded AZ31.Apatite formation and weight loss study was conducted for 7 days,14 days and 21 days after immersion tests in SBF solution.The perforated structure in AZ31 with 26 through micro-holes provides 72%increase in surface area but with marginally 4%higher weight loss as compare to non-perforated structure.Comparing perforated and non-perforated samples of Mg-alloy,it was well observed that perforated structure forms high volume of apatite as compared to non-perforated structure.Scanning electron microscopic(SEM)study revealed that in perforated structure,drilled holes retain their circularity after 21 days of immersion test and distinct corrosion phenomenon occur at localized sites.展开更多
基金This study was supported by State Grid Corporation Science and Technology Project“Research on Comprehensive Control Technology of Low Frequency Noise of Distribution Transformers in Residential Areas”(5216A019000P).
文摘This study investigates a dual-cavity resonant composite sound-absorbing structure based on a micro-perforated plate.Using the COMSOL impedance tube model,the effects of various structural parameters on sound absorption and sound insulation performances are analyzed.Results show that the aperture of the micro-perforated plate has the greatest influence on the sound absorption coefficient;the smaller the aperture,the greater is this coefficient.The thickness of the resonance plate has the most significant influence on the sound insulation and resonance frequency;the greater the thickness,the wider the frequency domain in which sound insulation is obtained.In addition,the effect of filling the structural cavity with porous foam ceramics has been studied,and it has been found that the porosity and thickness of the porous material have a significant effect on the sound absorption coefficient and sound insulation,while the pore size exhibits a limited influence.
基金supported by the Naval Research Board,Government of India(Grant No.DNRD/05/4003/NRB/220)
文摘Presence of the outer perforated cylinder reduces the direct wave impact on the inner cylinder, which has been testified by many researchers. However, the force reduction mechanism, which is complicated due to the wave-porous structure interaction, needs to be addressed in detail. The present study explains the mechanism with the aid of the computational fluid dynamics （CFD） tool STAR CCM＋. This package is chosen for its capabilities to simulate viscous and turbulence effects caused by passage of waves. For the present study, flow fields around the twin cylinders with different orientations are examined with and without the outer perforated cover. Mechanism contributing to the reduction of force on the existing structure is explained in physical terms, and force reduction is quantified. The present study has direct application in the retrofitting application of offshore members.
文摘Porous structures are highly preferred for bone regeneration and high tissue in-growth.In present work,electrical discharge drilling(EDD),a thermal erosion process was used to produce through holes in Mg-alloys to fabricate perforated structure similar to open cell porous structure in extruded AZ31.Apatite formation and weight loss study was conducted for 7 days,14 days and 21 days after immersion tests in SBF solution.The perforated structure in AZ31 with 26 through micro-holes provides 72%increase in surface area but with marginally 4%higher weight loss as compare to non-perforated structure.Comparing perforated and non-perforated samples of Mg-alloy,it was well observed that perforated structure forms high volume of apatite as compared to non-perforated structure.Scanning electron microscopic(SEM)study revealed that in perforated structure,drilled holes retain their circularity after 21 days of immersion test and distinct corrosion phenomenon occur at localized sites.
