Velocity measurement of He II thermal counterflow jet accompanied by second sound Helmholtz oscillation
✍ Scribed by A. Nakano; M. Murakami
- Publisher
- Elsevier Science
- Year
- 1994
- Tongue
- English
- Weight
- 608 KB
- Volume
- 34
- Category
- Article
- ISSN
- 0011-2275
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✦ Synopsis
A laser Doppler velocimeter (LDV) is applied to the measurement of a thermal counterflow jet in He I1. It is capable of direct measurement of the normal fluid velocity. Detailed analysis of the velocity measurement results suggests that the normal fluid component entrains the surrounding superfluid component to result in a zero relative velocity flow between the normal and superfluid components, even very close to the nozzle exit. It is demonstrated that the second sound Helmholtz oscillation measurement is of use for diagnosis of the superfluid turbulent state in a jet. The variation in frequency and the decay of the oscillation as a result of tangled vortices-flow interaction were investigated for this purpose. It is also suggested that a weak superfluid turbulent state, apparently different from the Gorter-Mellink type superfluid turbulent state, may be reached in the case of small heat input. On the other hand, for large heat input, the turbulent state was identified as the Gorter-Mellink type superfluid turbulent state.