Transition to Superfluid Turbulence
Transition to Superfluid Turbulence
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过渡到超流体湍流
DOI：
10.1007/s10909-006-9229-1
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发表时间：
2006
影响因子：
2
通讯作者：
G. Volovik
中科院分区：
文献类型：
--
作者：
V. Eltsov;M. Krusius;G. Volovik
超流体中的湍流很大程度上取决于涡流运动中的耗散阻尼。这是在超流体 3He 的 B 相中观察到的，其中量子化涡旋的动力学特性随着温度的变化而发生根本性的变化。突然转变为湍流是最奇特的后果。与粘性流体动力学不同，这种向湍流的转变不受速度相关的雷诺数控制，而是由与速度无关的无量纲参数 1/q 控制，该参数仅取决于与温度相关的相互摩擦——当涡流相对于液体的法向激励移动时产生的耗散。在大摩擦和小值 $$1/q \lesssim 1$$ 时，动力学是涡旋数守恒的，而在低摩擦和大 $$1/q > rsim 1$$ 时，涡旋很容易不稳定并且数量激增。采用了一种新的测量技术来识别这种流体动力学转变：以相对较高的速度在应用的无涡流中注入许多小涡环的紧密束。当 3He-A 和 3He-B 两相样品旋转时，这些涡流从覆盖 AB 界面的涡流片中喷射出来，并且界面在临界旋转速度下变得不稳定，这是由超流体开尔文-亥姆霍兹不稳定性触发的。
Turbulence in superfluids depends crucially on the dissipative damping in vortex motion. This is observed in the B phase of superfluid 3He where the dynamics of quantized vortices changes radically in character as a function of temperature. An abrupt transition to turbulence is the most peculiar consequence. As distinct from viscous hydrodynamics, this transition to turbulence is not governed by the velocity-dependent Reynolds number, but by a velocity-independent dimensionless parameter 1/q which depends only on the temperature-dependent mutual friction—the dissipation which sets in when vortices move with respect to the normal excitations of the liquid. At large friction and small values of $$1/q \lesssim 1$$ the dynamics is vortex number conserving, while at low friction and large $$1/q > rsim 1$$ vortices are easily destabilized and proliferate in number. A new measuring technique was employed to identify this hydrodynamic transition: the injection of a tight bundle of many small vortex loops in applied vortex-free flow at relatively high velocities. These vortices are ejected from a vortex sheet covering the AB interface when a two-phase sample of 3He-A and 3He-B is set in rotation and the interface becomes unstable at a critical rotation velocity, triggered by the superfluid Kelvin–Helmholtz instability.