Packard has observed the intersection of vortex lines with the free surface of the fluid, and Avenel and Varoquaux have studied the Josephson effect in superfluid helium-4.
12.
It is only through dissipation of a vortex due to viscosity that a vortex line can end in the fluid, rather than at the boundary of the fluid.
13.
At the dynamic level, the fact that vortex lines are transported by any flow governed by the classical Euler equations implies conservation of any vortical structure within the flow.
14.
There was much communication between the two men on the subject of vortex lines, with many references to the application of their theorems to the study of smoke rings.
15.
H is invariant precisely because the vortex lines are frozen in the flow and their linkage and / or knottedness is therefore conserved, as recognized by Lord Kelvin ( 1868 ).
16.
In quantum turbulence, these vortex lines are real they can be observed, and have a very definite circulation and moreover they provide the whole of the physics of the situation.
17.
In the case of two-dimensional Josephson junctions ( thick long Josephson junctions with an extra dimension ) described by the 2D sine-Gordon equation, shape waves are distortions of a Josephson vortex line of an arbitrary profile.
18.
Historically, a vortex has been thought of as a region in the flow where a group of vortex lines come together hence indicating the presence of a vortex core, with groups of instantaneous circular paths about the core.
