The evolution of vortices on the surface of normal He I

摘要

Thermogravitational convection (Rayleigh-Benard convection, RBC) occurs in a layer of normal He I heated from above, at temperatures below the liquid density maximum of He-4 T <= T-m = 2.178 K. It is experimentally established that the appearance of RBC in the bulk of the layer is accompanied by the excitation of a vortex flow on the free surface of He I. With time, small vortices form two large-scale vortices (vortex dipole) in a cylindrical vessel, the dimensions of which are limited by the vessel's diameter. As the temperature of the liquid rises above T-m, the convective motion in the bulk of the nonuniformly heated layer rapidly decays, but the vortex flow on the surface of He I is conserved. The results of studying the vortex system evolution in the absence of RBCs (without energy pumping) show that, during long-term observations (over 1300 s), the non-linear interaction between weakly damped large-scale vortices leads to the appearance of small vortices on the surface of He I. Published under license by AIP Publishing.