Lagrangian accelerations of particles in superfluid turbulence

Quantum turbulence in thermal counterflow of superfluid He-4 is studied at length scales comparable to the mean distance l between quantized vortices. The Lagrangian dynamics of solid deuterium particles, of radius R-p about one order of magnitude smaller than l, is analysed in a planar section of the experimental volume by using the particle tracking velocimetry technique. We show that the average amplitude of the acceleration of the particles seems to increase as the temperature decreases and applied heat flux increases and this can be explained by exploiting the two-fluid model of superfluid He-4. We also report that, at the probed length scales, the normalized distribution of the acceleration of the particles appears to follow an unexpected classical-like behaviour.