Experimental investigations on turbulent Taylor-Couette flows in very wide gaps (part 2)

极宽间隙中泰勒-库埃特湍流的实验研究（第 2 部分）

• 批准号: 422002662
• 负责人: Professor Dr.-Ing. Christoph Egbers
• 金额: --
• 依托单位: Lehrstuhl Aerodynamik und Strömungslehre
• 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/422002662?language=en
• 关键词: Experimental; investigations; turbulent; Taylor; Couette

The proposed work is the second phase of the project ‘Experimental investigation of turbulent Taylor-Couette (TC) in very wide gaps’. The objectives of this work are divided into two groups: one concentrating on the flow in the centrifugally unstable regime and based on the scientific open questions posed in the project's first phase, and the other researching the flow in the centrifugally stable regime, specifically the quasi-Keplerian flow (η²≤µ≤1), where this flow regime was not addressed in the project’s first phase. Here, the existing experimental apparatus (TvTCC) will be used in the first part to further analyze existing flow parameters. While a new system is proposed to be built with a larger geometry that allows measurements of the flow structures with significantly higher spatial and temporal resolution and direct torque measurements. The visualization of the very wide gap TC flow (η = 0.1) in the counter-rotating regime shows the existence of a variety of flow patterns, where some of these patterns are found to be unique to this geometry (e.g., Axial Columnar vortex, Helical Columnar vortex, etc.). The mechanics responsible for this set of patterns are still an open question and will be addressed in this work. Moreover, the angular momentum transport dependence on the rotation rate in η = 0.1 shows a maximum of transport for low counter-rotating rates, where the large-scale circulation (LSC) fulfills the whole gap and enhances the transport of the angular momentum flux. As counter-rotating rates increase, the LSC detaches from the outer cylinder wall due to the outer rotation stabilizing effect and leads to a decrease in momentum transport until it achieves a minimum. Unexpectedly, and for higher counter-rotating rates, the angular momentum transport starts to increase again, despite the apparently stabilizing effect of the outer cylinder rotation. The flow's space-time analysis indicates that the presence of inward-propagating patterns developed near the outer cylinder wall leads to this increase in angular momentum transport at high counter-rotating rates. Since these novel patterns arise in a centrifugally stable region, it is unclear what instability is responsible for them. The proposed work will focus on studying the dynamics of the outer boundary layers where these patterns appear and further studying the analogy between these patterns and the shear-induced superstructures that appear in other wall-bounded flows (pipe, channel, etc.). For TC flow in the centrifugal stable regime, numerous studies tried to find a subcritical hydrodynamic instability to bring turbulence into account. However, in the very wide-gap flow (η = 0.1), structures have been found that are assumed to contribute to the overall angular momentum transport. Further identification and quantification of these patterns are needed, in addition to the quantification of the global angular momentum transport for the flow in the centrifugally stable regime.

拟议的工作是项目“在非常宽的差距中的湍流泰勒 - 库特（TC）的实验投资”项目的第二阶段。这项工作的目标分为两组：一个集中在离心不稳定的政权中的流程，并基于该项目第一阶段中提出的科学开放问题，另一个研究了离心稳定政权中的流动，特别是准键盘流动性流动（η标符≤1），该流程度未解决该项目的第一个阶段。在这里，将在第一部分使用现有的实验设备（TVTCC），以进一步分析现有的流程参数。虽然提议使用较大的几何形状构建新系统，该几何形状允许测量具有明显更高的空间和临时分辨率以及直接扭矩测量值的流量结构。在反向旋转状态中，非常宽的GAP TC流（η= 0.1）的可视化显示了各种流动模式，其中某些模式被认为是该几何形状所独有的（例如，轴向柱状涡流，螺旋柱柱圆柱涡旋等）。负责这组模式的机制仍然是一个悬而未决的问题，将在这项工作中解决。此外，角动量转运依赖于η= 0.1的旋转速率显示出低相位率的最大传输，其中大规模循环（LSC）满足了整个间隙并增加了角动量磁通量。随着反旋转速率的增加，由于外缸壁由于外缸的运输而导致的外部气缸壁引起的外部气缸壁脱离，直到达到最低为止。出乎意料的是，对于更高的反向旋转速率，角动量传输再次开始增加，dospite显然是外缸旋转的稳定效应。流动的时空分析表明，在外缸壁附近发生的内向传播模式的存在导致在高反向旋转速率下增加角动量传输。由于这些新颖的模式出现在一个离心稳定的区域，因此尚不清楚哪种不稳定性是造成它们的。拟议的工作将着重研究这些模式出现的外边界层的动力学，并进一步研究这些模式与剪切诱导的上层建筑之间出现的类比，这些上层结构出现在其他壁构成的流中（管道，通道等）。对于离心稳定制度中的TC流动，许多研究试图发现亚临界水动力不稳定以考虑到湍流。但是，在非常宽的差距（η= 0.1）中，发现结构被认为有助于整体角动量转运。除了定量离心稳定机制中的全局角动量转运外，还需要对这些模式进行进一步的识别和定量。