Local heat flux in turbulent Rayleigh-Bénard convection

气候预测和天气预报、污染物在大气和海洋中的传播以及室内房间的高效供暖或制冷基本上是基于数值模型，其中必须考虑各种物理和化学过程。热对流是这些因素之一。然而，其在强湍流中的模拟目前仍存在很大的不确定性。申请者打算在世界范围内最大的对流实验--伊尔梅瑙桶中研究瑞利数Ra=10^12的湍流热传输。在直径为7.15m的Rayleigh-Bénard环流中，利用局地热流探头和红外摄像技术测量了局地热流的分布和时间演化。特别是，将系统地研究这种分布如何取决于纵横比--单元格的横向和垂直范围之间的比率。是否会像唯象标度理论中所提供的那样出现局部偏离平均热流密度的情况，这是有待证明的。

Climate prediction and weather forecast, the propagation of pollutants in the atmosphere and the oceans as well as an efficient heating or cooling of indoor rooms are essentially based on numerical models in which a great variety of physical and chemical processes has to be considered. Thermal convection is one of these factors. However, its simulation in highly turbulent flows is still very uncertain nowadays. The applicant intend to study turbulent heat transport up to a Rayleigh number of Ra=10^12 in the world-wide largest convection experiment - the Barrel of Ilmenau. Using both local heat flux probes and infrared camera technology the distribution and the temporal evolution of the local heat flux will be measured in the Rayleigh-Bénard cell of 7.15 m diameter. In particular, it will be studied systematically how this distribution depends on the aspect ratio - the ratio between the lateral and the vertical extent of the cell. It is to be shown whether or not local deviations from the mean heat flux may occur as provided in phenomenological scaling theories.