QFS2016 Book of Abstracts

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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