Characteristics of the transition to turbulence in superfluid He4 at low temperatures

Abstract

A piezoquartz oscillator (tuning fork) immersed in liquid is used to study the kinetic and dissipative processes in He II experimentally. The electrical response of the tuning fork near its resonance frequency is measured with different exciting voltages at temperatures ranging from 0.1Kto4.2K. The measured values of the half-width of the resonance curves made it possible to determine the viscosity of the normal component of He II in a wide temperature range. A maximum of the effective viscosity is found at temperature ∼0.5K; this maximum is due to a transition from the hydrodynamic to the ballistic regime in the phonon gas in He II. It is established that for low velocities of oscillation of the tuning fork the velocities are a linear function of the excitation force; this corresponds to laminar flow of the liquid in the boundary layer near the oscillating surface. The main dissipative process is associated with the viscosity of the normal component. The thickness of the boundary layer near the surface of the oscillating tuning fork is estimated. Kinks attesting to a transition to nonlinear flow are found in the dependence of the electric response on the excitation voltage for high velocities of the tuning fork. At low temperatures this regime is accompanied by the appearance of flat sections near the maximum in the resonance curves. This behavior can be explained by a transition from laminar to turbulent flow of the liquid, which likewise is accompanied by the appearance of additional dissipation due to the creation of quantum vortices. The critical velocity of the transition to the turbulent regime, whose temperature dependence qualitatively agrees with measurements performed previously using oscillating bodies of a different shape, is determined.

Hysteresis, Switching and Anomalous Behaviour of a Quartz Tuning Fork in Superfluid 4He

“…We have studied the hysteretic transition to and from laminar and turbulent states of a tuning fork in superfluid 4 He at millikelvin temperatures. There is rich preliminary data in Fig.…”

“…Two RuO 2 resistors are used one as a thermometer and one a heater. Most of the volume is occupied by silver sinter heat exchangers used to cool the 4 He sample (Color figure online)…”

Studies of kinetic processes in a concentrated 3He-4He solution using an oscillating tuning fork

“…Studies of kinetic processes in a concentrated 3 He- 4 He solution using an oscillating tuning fork 1. Introduction Recently, vibrating quartz tuning forks immersed in superfluid 4 He, have been widely used to study different processes within liquids, including the transition to a turbulent state, 1-4 viscosity, 5,6 the behavior of 3 He impurities, 7 etc.…”

“…In most experimental studies, the tuning forks were used to examine the properties of pure 4 He. As for a solution of 3 He in 4 He, the first details about the dissipative processes in the tuning fork-superfluid solution system are obtained in Ref.…”

Mutual interactions between objects oscillating in isotopically pure superfluid 4He in the T → 0 limit

“…They have been used as thermometers, viscometers and pressure sensors [15] in all the helium fluids, as well as in QT studies in He II. Forks have been shown [15,[17][18][19][20][21] to generate QT over a wide range of temperatures. The question naturally arises, therefore, as to whether forks can also act as detectors of vortex lines?…”