Collaborative Research: Materials World Network: Collaborative Research on Simple Forms of Quantum Turbulence - Production, Decay and Visualization

合作研究：材料世界网络：简单形式量子湍流的合作研究 - 产生、衰变和可视化

• 批准号: 1007937
• 负责人: Gary Ihas
• 金额: $ 50万
• 依托单位: University of Florida
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-09-01 至 2015-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1007937&HistoricalAwards=false
• 关键词: Collaborative; Research; Materials; World; Network

Turbulence in classical fluids is important and challenging both from a theory perspective and for many practical applications. This research, a collaboration between the University of Florida, Yale University, and the Universities of Lancaster, Manchester and Birmingham in the United Kingdom, aims to understand how classical turbulence is modified in a superfluid, such as liquid helium, in which flow is severely restricted by quantum conditions associated with the quantization of angular momentum and a complete lack of viscosity. Quantum turbulence has a character that depends on the temperature. Just below the superfluid transition temperature a superfluid behaves as a mixture of a normal (classical-like) fluid and a superfluid; either or both fluids can be turbulent, which gives rise to a rich variety of possible turbulent patterns At much lower temperatures only the superfluid component remains, exhibiting most clearly the fundamental aspects of quantum turbulence. The study of quantum turbulence would be greatly facilitated if the patterns of turbulent flow could be visualized. The use of micron-sized particles of hydrogen as tracers has been pioneered elsewhere, but the investigators in this project are implementing the use of much smaller particles in the form of metastable diatomic helium molecules, which will be observed by laser fluorescence. At temperatures somewhat below the superfluid transition such molecules are expected to follow the normal fluid, while at much lower temperatures they are expected to follow the quantized vortex motion in the superfluid component. In the earlier stages of the work the investigators will develop this technique for application in the more accessible temperature range where the molecules track the normal fluid, but where many important aspects of quantum turbulence have still to be studied and understood. The preliminary experiments will pave the way towards applications at lower temperatures. Also, since a very simple form of turbulence can be generated in the wake of a steadily moving grid, the investigators are developing techniques for moving a grid through superfluid helium at a very low temperature where the quantum turbulence involves only the normal fluid. The resulting turbulence will be studied on a global scale in two ways: observing the rate at which the superfluid heats up as a result of the decay of the turbulence; and using the scattering of ions to measure the rate at which the concentration of turbulent eddies decays. Success of the proposed experiments is dependent on the development of close interactive collaboration between Florida (development of the moving grid and study of energy dissipation behind it), Yale and Manchester (visualization), Birmingham (theory), Lancaster and Manchester (decay of the concentration of turbulent eddies behind a moving grid). Students and postdoctoral associates from all labs will work in the other labs both to promote the overall effort and further to develop each researcher?s capability. While the work is challenging because of the low temperature environment, the possible pay off is high, as an understanding of quantum turbulence may offer insights into classical turbulence which have heretofore escaped common understanding.

从理论的角度和许多实际应用中，经典流体的湍流都很重要，而且具有挑战性。这项研究是佛罗里达大学，耶鲁大学与英国兰开斯特，曼彻斯特和伯明翰大学之间的合作，旨在了解如何在超流体中修改古典湍流，例如液体氦气，其中流动受到与量子的量子条件的限制，与量子的量化相关，与量子动力和完全缺乏VESC质量相关的量子条件。量子湍流具有取决于温度的特征。 在超流体过渡温度下方，超流体的表现为正常（经典）流体和超氟的混合物。 无论哪种流体都可以是湍流，这会在低温下只有超级流体成分留下的多种可能的湍流模式，最清楚地表现出量子湍流的基本方面。如果可以看到湍流的模式，将极大地促进量子湍流的研究。 将微米大小的氢用作示踪剂的使用已在其他地方开创，但是该项目中的研究者正在以亚稳态的双原子氦分子的形式实施使用较小的颗粒，这将通过激光荧光观察到。 在低于超流体过渡的温度下，这种分子预计将遵循正常的流体，而在较低的温度下，预计它们将遵循超流体成分中量化的涡旋运动。 在工作的较早阶段，研究人员将开发该技术在更容易接近的温度范围内跟踪正常流体，但是在量子湍流的许多重要方面仍然需要研究和理解。 初步实验将为较低温度的应用铺平道路。同样，由于在稳定移动的网格之后可以产生一种非常简单的湍流形式，因此研究人员正在开发在非常低温的超级流体氦气中移动网格的技术，在极低的温度中，量子湍流仅涉及正常流体。 由此产生的湍流将以两种方式在全球范围内进行研究：观察超流体由于湍流衰减而加热的速率；并使用离子的散射来测量湍流涡流衰变的速率。拟议的实验的成功取决于佛罗里达州（移动网格的发展和其背后的能量耗散研究），耶鲁大学和曼彻斯特（可视化），伯明翰（理论），兰开斯特（Lancaster），兰开斯特（Lancaster）和曼彻斯特（曼彻斯特（Manchester）（衰败的动态网格背后的湍流涡流的衰减））。来自所有实验室的学生和博士后同伴将在其他实验室工作，以促进整体努力，进一步发展每个研究人员的能力。尽管由于低温环境，这项工作具有挑战性，但可能的回报很高，因为对量子湍流的理解可能会提供对经典湍流的见解，这些湍流迄今逃脱了共同的理解。