  Despite being a quantum two-fluid system, superfluid helium-4 (He II) is
observed to behave similarly to classical fluids when a flow is generated by
mechanical forcing. This similarity has brought up the feasibility of utilizing
He II for high Reynolds number classical turbulence research, considering the
small kinematic viscosity of He II. However, it has been suggested that the
non-classical dissipation mechanism in He II at small scales may alter its
turbulent statistics and intermittency. In this work, we report our study of a
nearly homogeneous and isotropic turbulence (HIT) generated by a towed grid in
He II. We measure the velocity field using particle tracking velocimetry with
solidified deuterium particles as the tracers. By correlating the velocities
measured simultaneously on different particle trajectories or at different
times along the same particle trajectory, we are able to conduct both Eulerian
and Lagrangian flow analyses. Spatial velocity structure functions obtained
through the Eulerian analysis show scaling behaviors in the inertial subrange
similar to that for classical HIT but with enhanced intermittency. The
Lagrangian analysis allows us to examine the flow statistics down to below the
dissipation length scale. Interestingly, strong deviations from the classical
scaling behaviors are observed in this regime. We discuss how these deviations
may relate to the motion of quantized vortices in the superfluid component in
He II.
