首页   按字顺浏览 期刊浏览 卷期浏览 Cavitation in Helium at Low Frequencies
Cavitation in Helium at Low Frequencies

 

作者: E. A. Neppiras,   T. Vroulis,   R. D. Finch,  

 

期刊: The Journal of the Acoustical Society of America  (AIP Available online 1971)
卷期: Volume 49, issue 1A  

页码: 73-74

 

ISSN:0001-4966

 

年代: 1971

 

DOI:10.1121/1.1975951

 

出版商: Acoustical Society of America

 

数据来源: AIP

 

摘要:

Previous studies showed that cavitation noise and the half‐order subharmonic occurred at much lower thresholds than required to produce macroscopic visible bubbles in the superfluid helium II. It might be supposed that this low “audible” threshold is associated with the presence of subvisible resonant bubbles. Accordingly experiments are in progress at lower frequencies in anticipation that any such bubbles will be larger in size with consequently less distinction between audible and visible thresholds. One investigation employed a sandwich‐type transducer coupled to the liquid through a velocity transformer operating at 9.93 kHz. Measurements of particle velocity were made by including the transducer as one arm of a Wheatstone bridge and monitoring the off‐balance voltage. Pressure thresholds could be deduced from this information assuming progressive wave radiation. In helium II, at a temperature of about 2.0°K, pressure amplitude thresholds were found to be as follows: for subharmonic generation 0.4 mbar; for white‐noise generation, 3.4 mbar; and for visible bubble generation about 30 mbar; i.e., there was still a large difference between audible and visible thresholds. A device designed to operate around 100 Hz is presently under construction.

 

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