Turbulent Convection in a Fluid Heated from Below

****技术摘要****湍流对流在许多地球物理、天体物理和工业过程中起着重要作用，但对它的理解仍然不完整。拟议的工作将主要扩展到普朗特数Pr[（运动粘度）/（热扩散系数）]在0.17至1.0范围内的流体，这仍然是相对未被探索的，并且可以在气体和气体混合物中获得。这个范围包括与地球大气相关的普朗特数0.7。调查将扩展到高达20的大宽高比（直径/高度）样品和高达10^15的超大瑞利数Ra （Ra是应用温差的无量纲测量）。围绕垂直轴旋转的影响将被研究，它引入了科里奥利力并改变了系统的行为（例如，旋转与地球大气中飓风的形成有关）。这些实验需要构造复杂的仪器和许多复杂过程的计算机自动控制。因此，对于我们的年轻同事来说，它们是一个非常好的训练场所。****非技术摘要****从下面加热的流体中的湍流对流在许多自然现象和工业中是极其重要的。它发生在地幔中，在那里它有助于大陆板块的运动并影响火山活动。在地球的外核，它决定了我们生活的磁场。它是太阳外层重要的热传递机制，因此影响我们环境的温度。它在许多工业过程中起着重要作用，在这些过程中，它的增强或抑制可能会产生重大的经济后果。这些应用范围从计算机应用中的微型热传输装置到发电厂的大型冷却系统。然而，科学家和工程师对这些过程仍有许多未知之处。拟议的工作将把我们对湍流对流的理解扩展到具有类似地球大气性质的流体；这一性质范围在实验室中还相对未被探索。这项工作还将扩展到绕其垂直轴旋转的样本。这种自转将对流体施加一种力，即科里奥利力，从而改变系统的行为，其方式与地球自转如何改变飓风和洋流的性质有关。这些实验需要构造复杂的仪器和计算机对许多复杂过程的自动控制。因此，对于我们的年轻同事来说，它们是一个非常好的训练场，他们中的许多人将发展成为下一代科学家和工程师的领导者。

****Technical Abstract****Turbulent convection plays a major role in numerous geophysical, astrophysical, and industrial processes, and yet its understanding remains incomplete. The proposed work will primarily extend its investigation to fluids with Prandtl numbers Pr [(kinematic viscosity)/(thermal diffusivity)] in the range from 0.17 to 1.0 which remains relatively unexplored and which is accessible in gases and gas mixtures. This range includes the Prandtl number of 0.7 relevant to Earth's atmosphere. Investigations will be extended to samples of large aspect ratio (diameter/height) up to 20 and to exceptionally large Rayleigh numbers Ra (Ra is a dimensionless measure of the applied temperature difference) up to 10^15. The effect of rotation about a vertical axis, which introduces the Coriolis force and modifies the behavior of the system, will be studied (rotation is relevant for instance to the formation of hurricanes in Earth's atmosphere). These experiments require the construction of complex apparatus and the automatic computer control of numerous intricate processes. Thus they are an exceptionally good training ground for our young coworkers. ****Non-technical Abstract****Turbulent convection in a fluid heated from below is of utmost importance in many natural phenomena and in industry. It occurs in Earth's mantle where it contributes to the motion of continental plates and influences vulcanism. In the outer core of the Earth it determines the magnetic field in which we live. It is the important heat-transport mechanism in the outer layer of the Sun and thus impacts the temperature of our environment. It plays a significant role in many industrial processes, where its enhancement or inhibition may have significant economic consequences. These applications range from miniature heat-transport devices in computer applications to the giant cooling systems of power plants. And yet much remains unknown to the scientist and engineer about these processes. The proposed work will extend our understanding of turbulent convection to fluids with properties similar to the Earth's atmosphere; this property range has remained relatively unexplored in the laboratory. The work will also be extended to samples that are rotated about their vertical axis. The rotation will exert a force on the fluid known as the Coriolis force and thus will change the behavior of the system in a manner related to how Earth's rotation modifies the nature of hurricanes and ocean currents. These experiments require the construction of complex apparatus and the automatic computer-control of numerous intricate processes. Thus they are an exceptionally good training ground for our young coworkers, many of whom will evolve into the leaders of the next generation of scientists and engineers.