Dissipation in two-fluid flow of HeII

Abstract

We have extended our previous measurements of the dissipation associated with superfluid turbulence in flows where the superfluid and normal-fluid velocities can be varied independently to include all quadrants of the $V_{\mathrm{n}}$-$V_{\mathrm{s}}$ plane. Three distinct types of dissipation exist in fairly well-defined regions of the plane. In one region the dissipation can be described by the simple mutual friction associated with homogeneous superfluid turbulence. The boundary of this region is the extension of the TI-TII transition observed in thermal counterflow. The dissipation in the second region is consistent with a phenomenological extension of the homogeneous model. In the third region the dissipation is very weak and not easily characterized.