Normal-fluid velocity measurement and superfluid vortex detection in thermal counterflow turbulence

A first-principles analysis, which self-consistently takes into account the collisions of tracer particles with quantum vortices, demonstrates that there exist feasible thermal counterflow turbulence particle image velocimetry experiments that, for sustained periods of time, very accurately record the normal-fluid velocity. Moreover, sporadic, abrupt, and readily discernible deviations of tracer particle velocity from normal-fluid velocity always correspond to nonarresting particle-vortex collisions of finite duration that do not nullify the experiment and allow unambiguous pointwise-accurate tracking of quantum vortex position.