Lagrangian Measurements and Large Eddy Simulation of Inertial Particles in Turbulent Flows with and without Large-Scale Anisotropy

pi计划为高雷诺数湍流中惯性粒子的运动开发一个大涡模拟（LES）子网格闭合，以捕获由于惯性粒子聚集而产生的平均浓度和波动。为了评估该模型，pi将利用最新的国家科学基金会主要研究仪器（MRI）资助下开发的最先进的粒子跟踪能力来研究von Karman旋流腔内惯性粒子对的动力学。pi将执行全分辨直接数值模拟（DNS）的各向同性，粒子负载湍流，并将这些结果与LES模型进行比较。第二组拉格朗日测量将集中于大尺度各向异性和不均匀性对粒子运动的影响。这些测量将在MRI资助下开发的高雷诺数风洞设备中进行。pi将从两个方面修改早期的实验。首先，通过在风洞试验段引入剪切发生器或平板，研究均匀湍流剪切流（HTSF）和湍流边界层（TBL）。其次，两个额外的相机将被整合到光学装置中，使3D粒子轨迹能够被测量，从而研究大尺度各向异性对粒子运动的影响。除了这些测量将提供的基本信息外，pi将在日益复杂的（现实的）流中测试LES，以发现模型的哪些元素需要进一步开发以适应大规模的各向异性。将使用新开发的谱码对HTSF进行带粒子的DNS，并测量拉格朗日粒子统计量。DNS将支持在实验无法达到的参数空间限制内对LES子网格闭合进行测试。此外，来自DNS的数据对实验中使用的粒子跟踪码进行了测试。计划中的拉格朗日测量和DNS将揭示平均速度梯度和粒子壁对粒子运动的影响，为LES模型提供一个重要的测试平台，以及通过出版物和公共网站向社区提供的新知识。在他们的职业生涯中，pi一直在大力参与外联活动。最近的活动包括为女孩举办的初中和高中活动，通过斯隆奖学金计划和NSF AGEP奖励的pi份额招募和指导少数民族研究生，以及在社区内开展环境宣传。pi最近还创建了湍流研究国际合作组织（ICTR），以促进与世界各地我们社区其他成员的互动。

CBET-0756510CollinsThe PIs plan to develop a large-eddy simulation (LES) subgrid closure for the motion of inertial particles in high-Reynolds-number turbulence that captures the mean concentration and fluctuations that arise due to inertial particle clustering. To assess the model, the PIs will exploit state-of-the-art particle tracking capabilities developed under a recent NSF Major Research Instrumentation (MRI) grant to study the dynamics of inertial particle pairs inside a von Karman swirl flow chamber. The PIs will perform fully-resolved direct numerical simulations (DNS) of isotropic, particle-laden turbulence and compare those results to the LES model. A second set of Lagrangian measurements will be focused on the impact of large-scale anisotropy and inhomogeneities on the motion of particles. These measurements will be carried out in a high- Reynolds-number wind tunnel facility developed under the MRI grant. The PIs will modify the earlier experiments in two ways. First, homogeneous turbulent shear flow (HTSF) and a turbulent boundary layer (TBL) will be studied by introducing a shear generator or a flat plate into the test section of the wind tunnel. Second, two additional cameras will be incorporated into the optical setup, enabling 3D particle trajectories to be measured allowing study of the effect of large-scale anisotropy on the motion of particles. Aside from the fundamental information these measurements will provide, the PIs will test the LES in increasingly complex (realistic) flows to discover what elements of the model would need further development to accommodate large-scale anisotropy. DNS of HTSF with particles will be performed using a newly developed spectral code, and Lagrangian particle statistics will be measured. DNS will support testing of the LES subgrid closure in limits of the parameter space that cannot be reached by the experiment. In addition, data from the DNS test the particle tracking codes used in the experiment. The planned Lagrangian measurements and DNS will uncover the effect mean velocity gradients and walls have on the motion of particles, providing an important testbed for the LES model, as well as new knowledge to be made available to the community via publications and a public web site. The PIs have been heavily involved with outreach throughout their careers. Recent activities include middle school and high school activities for girls, recruiting and mentoring of minority graduate students through the Sloan Fellowship program and the NSF AGEP award the PIs share, and outreach within the community on the environment. The PIs also recently created the International Collaboration on Turbulence Research (ICTR) to facilitate interactions with other members of our community throughout the world.