Küchler Christian, Ibanez Landeta Antonio, Moláček Jan, Bodenschatz Eberhard
Max-Planck-Institute for Dynamics and Self-Organisation, 37077 Göttingen, Germany.
Cornell University, Ithaca, New York 14853, USA.
Rev Sci Instrum. 2024 Oct 1;95(10). doi: 10.1063/5.0211508.
In the study of fluid turbulence, the Lagrangian frame of reference represents the most appropriate methodology for investigating transport and mixing. This necessitates the tracking of particles advected by the flow over space and time at high resolution. In the past, the purely spatial counterpart, the Eulerian frame of reference, has been the subject of extensive investigation utilizing hot wire anemometry that employs Taylor's frozen flow hypotheses. Measurements were reported for Taylor scale Reynolds number Rλ > 104 in atmospheric flows, which represent the highest strength of turbulence observed on Earth. The inherent difficulties in accurately tracking particles in turbulent flows have thus far constrained Lagrangian measurements to Taylor scale Reynolds numbers up to approximately Rλ = 103. This study presents the Lagrangian particle tracking setup in the Max Planck Variable Density Turbulence Tunnel (VDTT), where Taylor scale Reynolds numbers between 100 and 6000 can be reached. It provides a comprehensive account of the imaging setup within the pressurized facility, the laser illumination, the particles used, and the particle seeding mechanism employed, as well as a detailed description of the experimental procedure. The suitability of KOBO Cellulobeads D-10 particles as tracers within the VDTT is illustrated. The results demonstrate that there is no significant charge exhibited by the particles and that the impact of their inertia on the results is negligible across a wide range of experimental conditions. Typical data are presented, and the challenges and constraints of the experimental approach are discussed in detail.
在流体湍流研究中，拉格朗日参考系是研究输运和混合最合适的方法。这就需要以高分辨率跟踪流体中随时间和空间平流的粒子。过去，纯空间对应的欧拉参考系一直是利用采用泰勒冻结流假设的热线风速仪进行广泛研究的对象。在大气流动中报道了泰勒尺度雷诺数Rλ>104的测量结果，这代表了地球上观测到的最强湍流强度。到目前为止，在湍流中精确跟踪粒子的固有困难将拉格朗日测量限制在泰勒尺度雷诺数高达约Rλ = 103的范围内。本研究介绍了马克斯·普朗克可变密度湍流风洞（VDTT）中的拉格朗日粒子跟踪装置，在该风洞中可以达到100至6000之间的泰勒尺度雷诺数。它全面介绍了加压设施内的成像装置、激光照明、使用的粒子和采用的粒子播种机制，以及实验程序的详细描述。说明了KOBO Cellulobeads D - 10粒子作为VDTT内示踪剂的适用性。结果表明，粒子没有表现出明显的电荷，并且在广泛的实验条件下，它们的惯性对结果的影响可以忽略不计。给出了典型数据，并详细讨论了实验方法的挑战和限制。
