Visualization of He II counterflow around a cylinder

We report the experimentally investigated evolution of thermal counterflow across a cylinder in He II by using a modified particle tracking visualization technique with solidified hydrogen particles as tracers. It was found, for a relatively small velocity of the normal fluid, that the flow is similar to laminar flow over cylinder in classical fluids. Increasing the flow velocity leads to the appearance of a pair of normal fluid eddies downstream the cylinder. We confirm the existence of large scale eddies both upstream and downstream of the cylinder at the highest velocities achieved. In addition to the previously reported turbulent state, we confirm the existence of a state where more than one pair of eddies coexist downstream from the cylinder. (C) 2013 AIP Publishing LLC.