Visualization studies of forced flow liquid helium

标题：强制流动液氦的可视化研究PI：Steven W.Van Sciver，FSUCo-Pi：Sylvie Fuzier，FU我们开展了一项实验研究工作，开发并应用粒子图像测速(PIV)技术来研究高雷诺数、强制流动液氦中的流体动力学过程。这项工作很有意义，因为液氦是一种具有特殊性质的特殊流体。特别是，氦有两个液相：He I，一种在T_c=5.2K和T=2.176 K之间存在的近经典流体，以及T以下的He II或超流氦，它是一种量子流体。He II显示了在任何其他流体中看不到的热流体特性。这些特性中的许多都有利于超导磁体和加速器等大规模低温技术的运行。虽然液氦中的流体动力学过程已经通过压力和温度测量等常规宏观技术得到了广泛的研究，但直到最近才有人尝试研究支撑这些过程的微观现象。这种现象最好是使用现代流动诊断技术，如PIV。推进我们对液氦流体动力学的基本的、微观的理解代表了提议的项目的主要智力优点。这项工作主要是实验性质的，目的是可视化He I和He II中的流动现象。将研究两种构型：管道流动和绕过钝体(如圆柱体或球体)的流动，管道中包含的圆柱体或球体的流速高达约0.5m/S(对应于雷诺数在105106范围内)。预计的结果之一是首次观测到He I和He II中的速度边界层。随后，将在流道中放置圆柱体和其他钝体，并使用PIV再次研究物体周围的条件。在更广泛的背景下，液氦的粘度是所有凝聚流体中最低的，因此给流体动力学和传热学研究带来了在中等尺寸系统中实现非常高的雷诺数的能力。这些好处促使世界各地的许多实验室建立了使用液氦的高雷诺数流体动力学设施。然而，特别是在He II之前的PIV研究表明，悬浮粒子与液体之间的相互作用可能比假设的要复杂得多。因此，该项目的一个更广泛的影响将是通过提高对液氦系统PIV测量技术的理解，使它们对该领域的所有研究人员都有用。除了这些技术发展，拟议的计划还应该对工程专业学生的教育经验产生重大影响，包括那些来自代表性不足群体的学生。除了建议中描述的研究生PIV研究工作，我们还将设计几个较小规模的项目，适合本科生通过FAMU-FSU工程学院MEE系的高级设计班参与，或适合通过REU/RET计划在附近的国家强磁场实验室招募的暑期学生。这一独特的机会将为这些人提供在美国其他任何地方都无法获得的研究或设计经验；这种经验可能会导致他们在低温领域的职业生涯。

Title: Visualization studies of forced flow liquid helium PI: Steven W. Van Sciver, FSUCo-PI: Sylvie Fuzier, FSUWe undertake an experimental research effort to develop and apply Particle Image Velocimetry (PIV) techniques to the fundamental study of fluid dynamic processes in high Reynolds number, forced flow liquid helium. This work is of interest because liquid helium is an exceptional fluid with exceptional properties. In particular, helium has two liquid phases: He I, a near classical fluid existing at temperatures between Tc = 5.2 K and T = 2.176 K, and He II or superfluid helium below T, which is a quantum fluid. He II displays thermal fluid properties not seen in any other fluid. Many of these properties provide benefits to the operation of large-scale, low temperature technologies such as superconducting magnets and accelerators. Although the fluid dynamic processes in liquid helium have been extensively studied by conventional macroscopic techniques like pressure and temperature measurement, only very recently have there been attempts to investigate the micro-scale phenomena that underpin these processes. Such phenomena are best explored using modern flow diagnostic techniques such as PIV. Advancing our basic, micro-scale understanding of liquid helium fluid dynamics represents the principal intellectual merit of the proposed project. The work is mainly experimental in nature, and is aimed at visualizing flow phenomena in both He I and He II. Two configurations will be studied: duct flow and flow around bluff bodies such as cylinders or spheres contained in a duct with flow velocities up to about 0.5 m/s (corresponding to Reynolds numbers in the range of 105 to 106). One of the expected outcomes is the first-ever observation of the velocity boundary layer in He I and He II. Subsequently, cylinders and other bluff bodies will be placed in the flow channel and the conditions around the body studied again using PIV. In the broader context, liquid helium has the lowest viscosity of any condensed fluid and thus brings to fluid dynamics and heat transfer studies the ability to achieve very high Reynolds number in moderate size systems. Such benefits have inspired a number of laboratories world-wide to establish high Reynolds number fluid dynamics facilities using liquid helium. However, previous PIV studies in He II in particular have shown that the interaction between the suspended particles and the liquid may be more complex than assumed. Thus, one of the broader impacts of the project will be through improving the understanding of PIV measurement techniques for liquid helium systems so that they useful to all researchers in the field.In addition to these technical developments, the proposed program should also have a significant impact on the educational experience of engineering students, including those from under represented groups. In addition to the graduate student PIV research effort described in the proposal, we will also craft several smaller scale projects suitable for undergraduate student participation through the Senior Design class in the M E Department of the FAMU-FSU College of Engineering or for summer students recruited through the REU/RET program at the nearby National High Magnetic Field Laboratory. This unique opportunity will provide these individuals with a research or design experience unattainable anywhere else in the US; an experience that may lead to a career in the field of cryogenics.