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Abstracts
P3.14
Observation of Axial Flow and Vortex Produced by Cryogenic Motor
in Superfluid
4
He
H. Yano, K. Ohyama, K. Obara, and O. Ishikawa
Osaka City University, Graduate School of Science, Japan
We report a superfluid flow induced by a cryogenic motor immersed in superfluid
4
He. We mounted a motor with rotor blades at the bottom of a transparent
cylinder to observe the free surface of
4
He superfluid. We find that the rotating
blades induces a parabolic meniscus of superfluid
4
He, producing axial superfluid
flow in the cylinder. Secondly, we mounted the motor in a cylindrical box with
a small hole at the center of the top and a narrow channel at the bottom, to
produce a suction superfluid flow through the small hole. In this setup, we have
successfully produced a funnel-shaped vortex in superfluid
4
He.
P3.15
Novel dynamics of vortices in coflow quantum turbulence: vortices
trapped on an attractor
Ikawa Shinichi(1) Tsubota Makoto(1,2)
1) Department of Physics, Osaka City University, 3-3-138 Sugimoto,
Sumiyoshi-ku, Osaka 558-8585, Japan
2) OCU Advanced Research Institute for Natural Science and Technology
(OCARINA), Osaka City University,3-3-138 Sugimoto, Sumiyoshi-ku, Osaka
558-8585, Japan
We perform a numerical simulation of the dynamics of quantized vortices produced
by coflow in a square channel using the vortex filament model. Unlike the situation
in thermal counterflow, where the superfluid velocity vs and normal-fluid velocity
vn flow in opposite directions, in coflow, vs and vn flow in the same direction.
Quantum turbulence in thermal counterflow has been long studied theoretically
and experimentally, and its various features have been revealed. In recent years,
an experiment on quantum turbulence in coflow has been performed to observe
different features of thermal counterflow [1]. By supposing that vs is uniform
and vn takes the Hagen-Poiseuille profile, we calculate the coflow turbulence
[2]. Vortices preferentially accumulate on the surface of a cylinder for vs=vn by
mutual friction; namely, the coflow turbulence has an attractor. As the vortices
become dense on the attractor, they spread toward its interior by their repulsive
interaction. Then, the superfluid velocity profile induced by the vortices gradually
mimics the normal-fluid velocity profile. This is an indication of velocity matching,
which is an important feature of coflow turbulence.
[1] E.Varga, S.Babuin, and L.Skrbek, Physics of Fluids 27, 065101 (2015).
[2] Shinichi Ikawa and Makoto Tsubota, Phys. Rev. B 93, 184508 (2016).
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