Materials World Network: A Collaborative Experimental Investigation of Pure Quantum Turbulence in Superfluid 4He at Very Low Temperatures

经典流体中的湍流对于理论和许多实际应用都是重要的和具有挑战性的。本研究旨在了解超流体中经典湍流是如何被改变的。在超流体中，流动受到与角动量量子化和完全缺乏粘性相关的量子条件的严格限制。在更高的温度下，超流体表现出“双流体”行为，一种正常的流体与超流体组分共存，其中量子效应是重要的。 已经有强有力的证据表明，在这些温度下，大尺度上的湍流结构可以非常类似于它们的经典对应物，尽管作用于小尺度上的耗散过程非常不同。人们怀疑在非常低的温度下也存在类似的情况，在那里没有正常的流体，湍流衰减的简单机制也消失了。我们的计划旨在提供与这些低温有关的实验证据，在这些低温下，应该可以观察到非常纯粹形式的量子湍流的基本行为，湍流由稳定移动的网格或振荡的网格产生。振荡网格的机械行为将提供有关湍流成核的证据，并且使用拖曳网格的量热观测将测量湍流衰减，这不仅反映了小尺度上的耗散，而且反映了整体湍流结构。量子湍流是一个很有意义的研究课题，它的研究有助于更好地理解经典湍流。拟议实验的成功取决于佛罗里达、伯明翰、兰开斯特和基辅之间密切互动合作的发展。兰开斯特实验小组将做振动晶格工作，伯明翰的合作研究者将支持理论发展。基辅集团将利用其完整的芯片制造线开发微型热和压力传感器。 来自所有实验室的学生和博士后同事将在其他实验室工作，以促进整体努力，并进一步发展每个研究人员的能力。

Turbulence in classical fluids is important and challenging both for theory and for many practical applications. This research aims to understand how classical turbulence is modified in a superfluid, inwhich flow is severely restricted by quantum conditions associated with the quantization of angular momentum and a complete lack of viscosity.At higher temperatures, superfluids exhibit "two-fluid" behavior, a normal fluid coexisting with the superfluid component in which the quantum effects are important. There is already strong evidence that at these temperatures turbulent structures on large length scales can be very similar to their classical counterparts, although dissipative processes acting on small scales are very different. It is suspectedthat a similar situation exists at very low temperatures, where the normal fluid is absent, and where simple mechanisms for the decay of the turbulence have disappeared. Our program seeks to provide experimental evidence relating to these low temperatures, at which the fundamental behavior of very pure forms of quantum turbulence ought to be observable, the turbulence being generated by either a steadily moving grid or an oscillating grid. The mechanical behavior of the oscillating grid will provide evidence about the nucleation of turbulence, and calorimetric observations with the towed grid will measure turbulent decay, which reflects not only dissipation on small scales but also the overall turbulent structure. Quantum turbulence is of great intrinsic interest, and its study could lead to a better understanding of classical turbulence.Success of the proposed experiments is dependent on the development of close interactive collaboration between Florida, Birmingham, Lancaster and Kiev. The Lancaster experimental group will do the vibrating grid work, and the Birmingham Co-Investigator will support theory development. The Kiev group will use its full chip fabrication line to develop micro-size thermal and pressure sensors for the work. Studentsand postdoctoral associates from all labs will work in the other labs to both promote the overall effort and to further develop each researcher's capability.