PIV measurement of thermal counterflow in HeII

In this study, the Particle Image Velocimetry (PIV) technique is applied for obtaining a whole-field view of thermal counterflow velocity profile in He II. To properly visualize thermal counterflow and accurately measure its velocity profile, the dynamics of particles in He II is analyzed, and an efficient way of seeding solid particles into He H is applied in the experiment. Using commercially available micro spheres, normal fluid velocity in He II thermal counterflow is measured at various bath temperatures and heat fluxes. The measurement results are shown to be quantitatively in agreement with predictions based on thermal counterflow theory.