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

CBET-0756510 CollinsPI计划开发一种大涡模拟（LES）子网格闭合，用于高雷诺数湍流中惯性颗粒的运动，捕获由于惯性颗粒聚集而产生的平均浓度和波动。为了评估该模型，PI将利用根据最近NSF主要研究仪器（MRI）资助开发的最先进的粒子跟踪能力，研究冯卡门旋流室内惯性粒子对的动力学。PI将对各向同性、含颗粒湍流进行完全解析的直接数值模拟（DNS），并将这些结果与LES模型进行比较。第二组拉格朗日测量将侧重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施中进行。PI将以两种方式修改早期的实验。首先，将通过在风洞试验段中引入剪切发生器或平板来研究均匀湍流剪切流（HTSF）和湍流边界层（TBL）。第二，两个额外的相机将被纳入光学设置，使3D粒子轨迹被测量，允许研究大规模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还将在日益复杂的（现实的）流动中测试LES，以发现模型的哪些元素需要进一步开发以适应大尺度各向异性。将使用新开发的光谱代码进行HTSF与粒子的DNS，并测量拉格朗日粒子统计。DNS将支持测试的LES子网格关闭的参数空间的限制，不能达到的实验。此外，来自DNS的数据测试了实验中使用的粒子跟踪代码。计划中的拉格朗日测量和DNS将揭示平均速度梯度和壁对粒子运动的影响，为LES模型提供重要的测试平台，并通过出版物和公共网站向社区提供新的知识。PI在其职业生涯中一直积极参与外展活动。最近的活动包括针对女孩的中学和高中活动、通过斯隆奖学金计划和专业人士共享的NSF AGEP奖项招募和指导少数族裔研究生，以及在社区内开展环境外展活动。PI最近还创建了国际湍流研究合作组织（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.