The two-fluid model of superfluid in quantum turbulent state. Strange phenomena caused by the interaction between quantized vortices and a thermal component

We show our recent studies on fully coupled two-fluid dynamics in superfluid ⁴He. In this system, the quantized vortices and the normal fluid affect each other through the mutual friction. The recent visualization experiments found strange phenomena. In the thermal counterflow, the velocity fluctuations of the laminar normal fluid is anisotropic. The fluctuations are more intense in the streamwise direction, as compared to transverse direction. The anisotropic fluctuations should be caused by the coupled dynamics of the two fluids. We performed the simulation and analyzed the velocity fluctuations of the normal fluid in the thermal counterflow. We found that the quantum turbulence causes the anisotropic velocity fluctuations. Our results are consistent with recent visualization experiments. This agreement validates the model of the coupled dynamics. (author)