Experimental Analysis of Turbulent Superstructures in Thermal Convection by Time-Resolved Lagrangian Particle Tracking up to Very High Rayleigh Numbers

通过高达极高瑞利数的时间分辨拉格朗日粒子跟踪对热对流中的湍流上层结构进行实验分析

• 批准号: 429432497
• 负责人: Dr. Johannes Bosbach
• 金额: --
• 依托单位: Institut für Aeordynamik und Strömungstechnik (IAS)
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2019
• 资助国家: 德国
• 起止时间: 2018-12-31 至 2022-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/429432497?language=en
• 关键词: Experimental; Analysis; Turbulent; Superstructures; Thermal

With this proposal, we aim at application of several innovative measurement techniques to capturing turbulent superstructures (TSS) in Rayleigh-Bénard convection (RBC) in the classical turbulent regime and the ultimate state. Combination of the “Shake-The-Box” (STB) Lagrangian Particle Tracking method for densely seeded flows with long-lived microscopic soap bubbles as tracer particles, the data assimilation tool FlowFit and Temperature-Sensitive Paints (TSP), large scale measurements with high spatial and temporal resolution shall be enabled. The generated data will help improving the understanding of complex phenomena such as interactions between turbulent superstructures or large scale circulations (LSC), thermal plumes and turbulent background fluctuations by directly observing their dynamic interplay. Two different samples shall be addressed. The lower Ra (< 2·10^8) are accessed with a convection cell using water as working fluid. It has a quadratic horizontal section and a variable aspect ratio in the range of 4-10. Further, a cuboidal convection cell with a longitudinal aspect ratio variable between 5 and 10 will be used. It shall be operated within the ‘U-Boot’ of the Max-Planck-Institute for Dynamics and Self-Organization, employing pressurized Sulphur-Hexafluoride as working fluid. This procedure allows to access Rayleigh numbers up to 5·10^13. In specific, the following Goals and research questions shall be addressed with this proposal.Goals:1. Generate and observe turbulent superstructures in RBC under laboratory conditions 2. Establish STB / FlowFit and TSP as an experimental toolbox to study Lagrangian and Eulerian flow structures and statistics in RBC3. Extend the STB / FlowFit methodology to determine 3D temperature fields in parallel to the velocity fields by using temperature-sensitive particles4. Study turbulent RBC at moderately large aspect ratios (4..10) up to very high Ra (~10^13)Research questions:1. How do the generated TSS scale with the Rayleigh-number?2. How does the morphology and dynamics of the large scale flow structures change upon transition from LSC to TSS, i.e. with increasing aspect ratio?3. What are the mechanisms driving the dynamic interplay between small and large scale coherent flow / superstructures, such as thermal plumes, LSC and TSS or adjacent LSC? 4. How far does the actual geometry of the lateral confinement (rectangular, quadratic, circular) impact on the dimension and lateral arrangement of turbulent superstructures?5. How are the large scale flow structures (LSC / TSS) linked to the patterns observed just above the onset of convection?

通过此提案，我们旨在将几种创新的测量技术应用于雷利 - 贝纳德建筑（RBC）在经典动荡政权和最终状态中捕获湍流的上层建筑（TSS）。 “摇盒”（STB）Lagrangian粒子跟踪方法的结合，用于带有长期微观肥皂泡作为示踪剂颗粒，数据同化工具流量拟合和温度敏感涂料（TSP），具有高空间和临时分辨率的大型测量的数据同化工具流量（TSP）。生成的数据将有助于提高对复杂现象的理解，例如湍流上层建筑或大规模循环（LSC）之间的相互作用，通过直接观察其动态相互作用，热羽和湍流背​​景波动。应解决两个不同的样本。使用水作为工作流体，使用转换单元访问下RA（<2·10^8）。它具有二次水平截面和4-10范围内的可变纵横比。此外，将使用具有纵向纵横比变量5到10之间的立方体连接细胞。它应在Max-Planck-Institute的动力学和自组织的“ U-Boot”中进行操作，并采用加压的硫磺氟氟乙烯作为工作流体。此过程允许访问最高5·10^13的瑞利号码。具体而言，本提案应解决以下目标和研究问题。目标：1。在实验室条件下，在RBC中生成和观察湍流的上层建筑2。建立STB / FlowFit和TSP作为研究Lagrangian和Eulerian流动结构和RBC3中的统计的实验工具箱。扩展STB / FlowFit方法，以使用温度敏感的粒子并平行于速度场确定3D温度场。研究湍流的RBC以中等大的纵横比（4..10）的高度（〜10^13）研究问题：1。生成的TSS如何用雷利数字缩放？2。从LSC到TSS的过渡时，大规模流量结构的形态和动力学如何变化，即纵横比的增加？3。哪些机制是什么机制驱动小规模和大规模相干流 /上层建筑之间的动态相互作用，例如热羽，LSC和TSS或相邻的LSC？ 4。横向限制的实际几何形状（矩形，二次，圆形）对湍流上层建筑的维度和横向排列的影响有多远？ 5。如何链接到在转换开始上方观察到的模式的大规模流量结构（LSC / TSS）？