3He-Superfluid-4He Mixtures: Convection, Anomalous Thermal Conductivity, and Boundary Resistance

摘要 技术摘要： 该项目将解决两个科学问题：非常稀的超流氦混合物中的异常热流和超流氦混合物中的对流。 异常热流研究的目的是了解氦3浓度趋于零时超流混合物有限热导率的实验观测结果。 这些观测结果与理论相冲突，理论预测，当氦三浓度为零时，热导率接近无穷大。 这项工作将使用交流电技术，以分离流体和其他热流路径，提供有关边界电阻的信息。对流研究的目的是描述超流混合物中的对流流动。实验技术将产生的图案和热流数据属于范围广泛的普朗特数。所要研究的问题涉及Rayleigh-Benard对流模式和时空混沌，模式形成系统的不稳定性和混沌状态。 非技术摘要：对流和热流将在氦3和超流氦4的混合物中进行研究。 从技术角度来看，超流氦4是有趣的，因为其有效的无限导热性使其成为从冷却的电子设备中提取热量的杰出流体。 其目的是潜在地减少由天然存在的氦3引起的对该系统中的热流的限制。 还计划描述对流氦中的非线性动力学和混沌。 对流发生在环境（大气，海洋，技术过程）中，它是研究非线性动力学和模式形成的更广泛主题的杰出系统。 超流体混合物具有与液态金属和半导体相似的性质，更好地了解氦中的对流可能与纯化这些材料有关。

Abstract Technical abstract: This project will address two scientific issues: anomalous heat flow in very dilute superfluid helium mixtures, and convection in superfluid helium mixtures. The objective of the anomalous heat flow study is to understand experimental observations of a finite thermal conductivity of superfluid mixtures as the helium 3 concentration goes to zero. These observations conflict with theory that predicts that the thermal conductivity approaches infinity as the helium three concentration goes to zero. The work will use alternating current techniques in order to separate fluid and other heat flow paths, providing information on the boundary resistance. The objective of the convection study is to characterize convective flows in superfluid mixtures. The experimental techniques will yield pattern and heat flow data which pertain to a broad range of Prandtl numbers. The issues to be investigated concern Rayleigh-Benard convection patterns and spatio-temporal chaos, instabilities of pattern forming systems, and chaotic states. Non-technical abstract: Convection and heat flow will be investigated in mixtures of helium 3 in superfluid helium 4. Superfluid helium 4 is interesting from a technical viewpoint, because its effectively infinite heat conductivity makes it an outstanding fluid for extracting heat from cooled electronic devices. It is aimed to potentially reduce limits to heat flow in this system caused by the naturally present helium 3. It is also planned to characterize nonlinear dynamics and chaos in convecting helium. Convection occurs in the environment (atmosphere, ocean, technical processes), and it is an outstanding system for studying the broader topic on nonlinear dynamics and pattern formation. Superfluid mixtures have similar properties to liquid metals and semiconductors, and a better understanding of the convection in helium is potentially relevant to purifying these materials.