Emergence of small-scale mixing in a T-mixer

T 型混合机中小规模混合的出现

• 批准号: 511099203
• 负责人: Professor Dr. Marc Avila Canellas
• 金额: --
• 依托单位: Zentrum für angewandte Raumfahrttechnologie und Mikrogravitation (ZARM)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/511099203?language=en
• 关键词: Emergence; small; scale; mixing; mixer

The efficient mixing of fluids is key in many applications in chemical, mechanical, environmental and aerospace engineering. Typical examples range from chemical reactors to combustion chambers, but also the dispersion of contaminants in the ocean or atmosphere. The mixing rate is given by the surface of contact between the two fluids and the mass-diffusion coefficient. In most applications, turbulence sets the mixing rate, because eddies occurring at multiple scales strongly deform and convolute the surface between the fluids. In turbulence, the largest eddies are prescribed by the geometry, whereas the smallest possible eddies are found at the Kolmogorov scale. By contrast, the scalar concentration exhibits fluctuations down to the Batchelor scale, which in liquids is over an order of magnitude smaller than the Kolmogorov scale. As a consequence, in liquids, the small-scale properties of turbulent mixing remain poorly understood at a fundamental level, which prevents the scale-up of chemical reactions in many systems. In this proposal, mixing is experimentally investigated in a T-mixer setup with long inlets, which allow fully developed inflows. The mixing channel has a hydraulic diameter of four centimeters which results in a Batchelor scale of tenths of micrometers in the regime of interest. This will be resolved in the experiments with high-resolution laser-induced fluorescence. The research in this proposal will yield a better understanding of small-scale mixing in turbulence, and more specifically of how this emerges and is influenced by flow transitions as the Reynolds number increases.

流体的有效混合是化学、机械、环境和航空航天工程许多应用的关键。典型的例子包括从化学反应器到燃烧室，以及海洋或大气中污染物的扩散。混合速率由两种流体之间的接触表面和质量扩散系数给出。在大多数应用中，湍流决定了混合速率，因为在多个尺度上发生的涡流会使流体之间的表面强烈变形和卷曲。在湍流中，最大的涡流是由几何形状决定的，而最小的涡流是在柯尔莫哥洛夫尺度上发现的。相比之下，标量浓度表现出低至巴彻勒标度的波动，在液体中，巴彻勒标度比柯尔莫哥洛夫标度小一个数量级。因此，在液体中，湍流混合的小尺度特性在基础层面上仍然知之甚少，这阻碍了许多系统中化学反应的放大。在该提案中，在具有长入口的 T 型混合器装置中对混合进行了实验研究，该装置允许充分发展流入。混合通道的水力直径为四厘米，这导致感兴趣区域的巴彻勒尺度为十分之一微米。这将在高分辨率激光诱导荧光实验中得到解决。本提案中的研究将更好地理解湍流中的小规模混合，更具体地了解随着雷诺数的增加，这种混合是如何出现的以及如何受到流动转变的影响。