Quantum Turbulence Triggered by Counterflow in a Connecting Tube

If we confine superfluid helium in two bulk chambers, named A and B, connected by a tube, it is known that heat injected into chamber A will force the normal-fluid component to flow from chamber A to B and the superfluid component to flow in the opposite direction. We also know that quantum turbulence can be generated by this thermal counterflow when it exceeds critical values. We measured the vortex line density by the second sound attenuation in chambers A and B. The results showed that the heater power required for the turbulence transition was lower in chamber B than in chamber A, even though the superfluid was flowing toward chamber A. This asymmetry suggests that the mechanisms for generating turbulence in each chamber are different. In chamber A, the quantum turbulence was generated by the thermal counterflow converging toward the tube near the inlet of the tube. In chamber B, in contrast, it was generated while simultaneously being transported by the counterflow jet flowing out of the tube.