Lagrangian velocity distributions in thermal counterflow of superfluid 4He

Abstract

Quantum turbulence in thermal counterflow of superfluid 4He is visualized and studied at length scales comparable to the average distance between quantized vortices. The lagrangian velocities of micrometer- sized deuterium particles are obtained in a planar section of the flow field by using the particle tracking velocime- try technique. It is shown that the lagrangian velocity normalized distributions are strongly non-gaussian, with power-law tails, in contrast to the nearly gaussian distributions obtained in classical turbulent flows. The average distance between quantized vortices can therefore be seen as the length scale indicating the transition between classical-like and quantum behavior in thermal counterflow of superfluid 4He.