Generation of turbulence by vibrating forks and other structures in superfluidH4e
Generation of turbulence by vibrating forks and other structures in superfluidH4e
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通过振动叉和其他结构在超流体中产生湍流H4e
DOI：
10.1103/physrevb.79.054522
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发表时间：
2009
影响因子：
3.7
通讯作者：
W. Vinen
中科院分区：
文献类型：
--
作者：
M. Blažková;D. Schmoranzer;L. Skrbek;W. Vinen
本文研究了在$^{4}\text{H}\text{e}$超流相中振动的若干石英叉的叉尖上的阻力，特别注意在很宽的温度范围内从层流到湍流的转变。正常相中的行为与经典流体的行为一致，如已经报道的[Phys.Rev.E75，025302（2007）]。在超流相的行为相比，其他结构的振动超流$^{4}\text{H}\text{e}$，并指出相似之处和差异。我们专注于所观察到的行为的阻力系数作为速度的函数，并探讨这种行为所带来的问题。有证据表明，超流体成分中开始产生显着的湍流时会出现急剧的临界速度。在高速下，阻力系数趋于在经典流体中观察到的阻力系数，这表明通过相互摩擦强烈耦合的两种流体然后表现得像单个经典粘性流体。中间区域的行为似乎因情况而异。有证据表明，在某些结构的情况下，过渡到单流体的行为发生，而突然的速度，仅略大于尖锐的超流临界速度，但在其他结构的过渡是渐进的。观察值的超流临界速度和有效粘度的完全耦合的流体，并进行了讨论。有人建议，临界超流速度总是密切相似的耦合流体将预计将经历一个经典的过渡之间的流动，是严格的层流和一个显示第一不稳定性，和一个可能的原因进行了讨论。
A study of the drag on the prongs of a number of quartz forks vibrating in the superfluid phase of $^{4}\text{H}\text{e}$ is reported, and particular attention is paid to the transitions from laminar to turbulent flow over a wide range of temperature. Behavior in the normal phase is consistent with that for a classical fluid, as has already been reported [Phys. Rev. E 75, 025302 (2007)]. Behavior in the superfluid phase is compared to that of other structures vibrating in superfluid $^{4}\text{H}\text{e}$, and similarities and differences are noted. We focus on the observed behavior of the drag coefficient as a function of velocity, and the problems posed by this behavior are explored. There is evidence for a sharp critical velocity at which significant turbulence starts to be generated in the superfluid component. At high velocities the drag coefficient tends to that observed in a classical fluid, suggesting that the two fluids, strongly coupled by mutual friction, are then behaving like a single classical viscous fluid. Behavior in the intermediate region seems to vary from one case to another. Evidence is presented that in the case of some structures the transition to single-fluid behavior takes place rather abruptly at a velocity that is only slightly greater than the sharp superfluid critical velocity, but that in other structures the transition is more gradual. Observed values of both the superfluid critical velocity and the effective viscosity of the fully coupled fluids are presented and discussed. It is suggested that the critical superfluid velocity is always closely similar to that at which the coupled fluids would be expected to undergo a classical transition between a flow that is strictly laminar and one that displays the first instability, and a possible reason is discussed.