Multiple critical velocities in oscillatory flow of superfluid 4He due to quartz tuning forks

We report recent investigations into the transition to turbulence in superfluid $^4$He, realized experimentally by measuring the drag forces acting on two custom-made quartz tuning forks with fundamental resonances at 6.5 kHz and 55.5 kHz, in the temperature range 10 mK to 2.17 K. In pure superfluid in the zero temperature limit, three distinct critical velocities were observed with both tuning forks. We discuss the signicance of all critical velocities and associate the third critical velocity reported here for the first time with the development of large vortical structures in the flow, which thus starts to mimic turbulence in classical fluids. The interpretation of our results is directly linked to previous experimental work with oscillators such as tuning forks, grids and vibrating wires, focusing on the behavior of purely superfluid $^4$He at very low temperature

Fázový diagram proudění supratekutého helia

The possibility of existence of the flow phase diagram for the helium superfluids is discussed based on the available experimental data

Quantum storm in a cold cup

summary:Kvantová turbulence, projevující se zejména klubkem kvantovaných vírů, vzniká v kvantových tekutinách, jejichž neobyčejné vlastnosti vysvětluje spíše kvantová než klasická fyzika. Popíšeme dvě nedávno identifikované limitní formy trojrozměrné kvantové turbulence a dvojrozměrnou turbulenci, až donedávna matematickou idealizaci, která se stala experimentální realitou

Quantum storm in a cold cup

Quantum turbulence, which manifests itself via a tangle of quantized vortices, occurs in quantum fluids, whose properties depend on quantum physics rather than classical physics. Here we report on two limiting forms of quantum turbulence which have been identified and how two-dimensional turbulence, until recently a mathematical idealization, has become experimental reality

Applications of the quartz tuning fork in classical and superfluid hydrodynamics

We present a short review of the multitude of applications of the commercially produced quartz tuning fork in cryogenic fluid dynamics, using cold gaseous, normal liquid and superfluid 4He as working fluids with extraordinary, but well-known and tunable physical properties. While the central focus of this work is the use of the tuning fork as a detector of classical and quantum turbulence, we also report other studies and applications, mainly on cavitation, pressure-, thermo- and viscosimetry. Finally, we mention briefly our recent studies of the acoustic emission due to these high-Q oscillators and its effect on the characteristics of their resonance