Anisotropic Formation of Quantum Turbulence Generated by a Vibrating Wire in Superfluid $${}^{4}\hbox {He}$$

Abstract

To investigate the formation of quantum turbulence in superfluid \({}^{4}\hbox {He}\), we have studied the emission of vortex rings with a ring size of larger than 38 \(\upmu \hbox {m}\) in diameter from turbulence generated by a vibrating wire. The emission rate of vortex rings from a turbulent region remains low until the beginning of high-rate emissions, suggesting that some of the vortex lines produced by the wire combine to form a vortex tangle, until an equilibrium is established between the rate of vortex line combination with the tangle and dissociation. The formation times of equilibrium turbulence are proportional to \(\varepsilon ^{-1.2}\) and \(\varepsilon ^{-0.6}\) in the directions perpendicular and parallel to the vibrating direction of the generator, respectively, indicating the anisotropic formation of turbulence. Here, \(\varepsilon \) is the generation power of the turbulence. This power dependence may be associated with the characteristics of quantum turbulence with a constant energy flux.