project title: Developed Superfluid Turbulence
project leader: Prof. Carlo Barenghi
access given (in days): 92
access used (in days): 79
local host: Prof. Grigory Volovik
home institution: Mathematics Dept., University of Newcastle
country of institution: U.K.
starting date (yyyy-mm-dd): 2004-04-15
New class of superfluid turbulence has been recently discovered in Helsinki in experiments with superfluid 3He-B. In contrast to classical turbulence, the transition to superfluid turbulence has been found to be velocity independent. According to recent theoretical analysis of coarse-grained hydrodynamic equations for superfluids with distributed vorticity, different types of developed superfluid turbulence may exist. The phase diagram of turbulent states in the plane of two relevant Reynolds parameters was suggested, and this diagram is consistent with the experiments in 3He-B and superfluid 4He. However, in this theoretical approach, based on the averaged equations, the real positions of quantum vortices in the vortex tangle is not known. The goal of the project is to identify these turbulent states and their development and decay in numerical analysis of the multi-vortex dynamics.
The computational model of quantum turbulence decay was developed employing a kinematic prescription for the normal fluid. It was found that after an initial transient, the length of the vortex tangle L decreases and for large times obeys a scaling law with a -0.45 exponent. The average magnitude (along the quantized vortices) of the superfluid and line-vortex velocity are close and differ significantly from the average magnitude of the normal fluid velocity. Publication: Demosthenes Kivotides, Quantum turbulence decay, Physics Letters A, volume 326, issues 5-6, pages 423-428 (2004).