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Convection and Critical Dynamics in Helium Three Superfluid Helium Four Mixtures

氦三超流氦四混合物中的对流和临界动力学

基本信息

批准号：
8714862
负责人：
Robert Behringer
金额：
$ 23.73万
依托单位：
Duke University
依托单位国家：
美国
项目类别：
Continuing Grant
财政年份：
1987
资助国家：
美国
起止时间：
1987-11-01 至 1991-04-30
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=8714862&HistoricalAwards=false
关键词：
Convection Critical Dynamics Helium Three

项目摘要

The proposed measurements, to be carried out using superfluid helium mixtures, will address a number of questions of considerable current interest. Using a pioneering flow visualization technique exploiting the interaction of thermal neutrons and helium three, they will obtain the first images of flows near the onset of convection in liquid helium. Additional measurements will use the very high temperature resolution obtainable at low temperatures and a variable geometry technique developed in this laboratory to further characterize these flows. Superfluid mixtures have a unique and very interesting parameter range in which the hydrodynamic instabilities of steady convection will change character. Using appropriate geometries, they will explore in detail these instabilities, the way they lead to chaos, and the way they are affected by the steady convection patterns. In a second set of measurements using the neutron imaging technique, they will establish the helium three profiles which are caused by the flow of heat in a superfluid mixture. By these measurements, they hope to understand recent data which show a striking violation of current theories describing the heat flow in these mixtures. The importance of the theories involved--Two-fluid Hydrodynamics and Dynamic Renormalization Group Theory--requires a careful examination of the heat flow problem in mixtures using a direct, but non- perturbative technique such as the neutron probe.

建议的测量，将使用超流体进行，氦混合物，将解决一些问题，当前的重大利益。使用一种开创性的流程可视化技术利用热的相互作用，中子和氦三，他们将获得第一张在液态氦中对流开始附近流动。额外测量将使用非常高的温度分辨率可在低温和可变几何技术下获得在这个实验室里开发的，以进一步表征这些流动。超流体混合物有一个独特而有趣的参数定常水动力不稳定性范围对流会改变性质。使用适当的几何形状，他们将详细探索这些不稳定性，导致混乱，以及他们受到稳定影响的方式对流模式在第二组测量中，中子成像技术，他们将建立氦三由超流体中的热流引起的轮廓混合物. 通过这些测量，他们希望了解最近的这些数据与当前的理论相悖描述了这些混合物中的热流。的重要性所涉及的理论--双流体流体力学和动力学重整化群理论--需要仔细研究混合物中的热流问题，使用直接的，但非微扰技术，如中子探测器。