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

Cornell University, Ithaca NY

Investigators

Abstract

CBET-0756510 Collins The 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.