Critical Velocity for Superfluid Turbulence at High Temperatures

Abstract

In rotating superfluid 3He‐B, a sharp transition to turbulence which is insensitive to the fluid velocity is observed in contrast to classical turbulence. Instead, this transition is controlled by an intrinsic parameter, q ≡ α/1 − α′, of the superfluid, where α and α′ are mutual friction parameters depending on temperature. However, rotating superfluid 3He‐B is the only system which shows this kind of transition, and many unsolved mysteries yet remain. Hence, we study numerically the quantum vortex dynamics in thermal (unidirectional) counter flow systems especially at high temperatures, with the goal of proposing a new system which also shows a turbulence transition controlled by q. It is shown that the critical velocity above which the system can sustain a vortex tangle increases sharply at q ≈ 0.4. This means that no vortex tangle state can be stable for q ≳ 0.4. This may be closely relevant to the dramatic vortex dynamics transition caused by q in rotating superfluid 3He‐B.