Quantum turbulence experiments: a direct look at vortex reconnections and Kelvin waves
by
Enrico Fonda(New York University)
→
Europe/Stockholm
122:026
122:026
Description
Liquid helium, as other cryogenic fluids, has a very low viscosity that
allows highly turbulent flows in compact experiments. However, unlike any
other fluid, when cooled below about 2.17K it becomes a superfluid, and it
can flow without any friction. Vorticity in superfluids is constrained to
line-like topological defects called quantized vortices. The evolution of a
tangle of these vortices defines a state known as quantum turbulence.
Quantum turbulence is in some ways similar to classical turbulence; for
example, both show a Kolmogorov energy spectrum. However, many features of
quantum turbulence, such as its velocity statistics, are distinct from
classical flows. Moreover, because of the absence of viscosity, the
dissipation mechanism in the zero-temperature limit must be different.
Theories suggest excitation of Kelvin waves following reconnection of
quantized vortices as the main dissipation mechanism. These helical waves
have been recently experimentally visualized and characterized for the
first time.
Paper