We report a laboratory study of the transport of angular momentum by a turbulent flow of an electrically conducting fluid confined in a thin disk. When the electromagnetic force applied to the liquid metal is large enough, the corresponding volume injection of angular momentum produces a turbulent flow characterized by a time-averaged Keplerian rotation rate $\overline{\mathrm{\Omega }}\sim r^{-3/2}$. Two contributions to the local angular momentum transport are identified: one from the poloidal recirculation induced by the presence of boundaries and the other from turbulent fluctuations in the bulk. The latter produces efficient angular momentum transport independent of the molecular viscosity of the fluid and leads to Kraichnan’s prediction ${\mathrm{Nu}}_{\mathrm{\Omega }}\propto \sqrt{\mathrm{Ta}}$. In this so-called ultimate regime, the experiment, therefore, provides a configuration analogous to accretion disks, allowing the prediction of accretion rates induced by Keplerian turbulence.

中文翻译：

---

液态金属中开普勒湍流的角动量传输

我们报告了一项关于通过限制在薄盘中的导电流体的湍流传输角动量的实验室研究。当施加在液态金属上的电磁力足够大时，角动量的相应体积注入会产生湍流，其特征在于时间平均开普勒旋转速率$\overline{\mathrm{\Omega }}～r^{-3/2}$. 确定了对局部角动量传输的两个贡献：一个来自边界存在引起的极向再循环，另一个来自体积中的湍流波动。后者产生独立于流体分子粘度的有效角动量传输，并导致 Kraichnan 的预测${怒}_{\mathrm{\Omega }}\propto \sqrt{塔}$. 因此，在这种所谓的终极状态下，该实验提供了一种类似于吸积盘的配置，从而可以预测开普勒湍流引起的吸积率。