Abstract
Flow due to a commercially available vibrating quartz fork is studied in gaseous helium, He I, He II and 3He–B, over a wide range of temperatures and pressures. On increasing the driving force, the flow changes in character from laminar (characterized by a linear velocity versus drive dependence) to turbulent (characterized by a square root velocity versus drive dependence). In classical fluids, we characterize this transition by a critical Reynolds number, Re c =U cr δ/ν, where U cr is the critical velocity, ν stands for the kinematic viscosity, $\delta=\sqrt{2\nu/\omega}$ is the viscous penetration depth and ω is the angular frequency of oscillations. U cr of order 10 cm/s observed in He II and 1 mm/s in 3He–B agree with those found with other vibrating objects such as spheres, wires and grids, as well as with available numerical simulations of vortex motion in an applied ac flow.
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