*******NON-TECHNICAL ABSTRACT******* This Faculty Early Career award supports a project to measure particle trajectories in turbulent fluids and granular flows. A novel system combining stereoscopic high speed imaging with real-time image processing will be developed to track the particles. This system has many similarities to the way the human visual system tracks objects, and it has potential for broad application. The studies are expected to help resolve key questions such as how turbulent trajectories depend on the method of creating the flow and how sediments are transported in turbulence. High-speed imaging will also be used to measure the rapid changes that occur in flowing grains. Granular materials can quickly transition between a fluid-like state with many collisions between particles and a stationary pile with no particle motion. The studies will guide the search for a better description of these transitions. These results would be of interest to industries such as agriculture and mining, where granular materials are widely used. Two educational and outreach initiatives will be pursued. Upper level undergraduate courses in quantum and classical mechanics, emphasizing the active engagement of students in learning through experimental activities, will be developed at Wesleyan University. Through a partnership with PIMMS (Project to Increase Mastery of Mathematics and Science), the faculty member will train elementary teachers in urban school districts in mastering the content of the physical science units they teach to their students. This project is co-funded by the Division of Materials Research (Condensed Matter Physics) and the Division of Chemical Transport Systems (Particulate and Multiphase Processes).
This Faculty Early Career award supports a project to develop our dynamical understanding of turbulent and granular flows through high-resolution optical particle tracking measurements. The project will develop a novel imaging design that uses stereoscopic high-speed imaging and real-time image processing to acquire 3D trajectories of particles advected in turbulent fluid flow. These studies will help resolve key questions about the universality of turbulent trajectories and the motion of large and non-neutrally buoyant particles in turbulent flows. In granular flows, precision particle tracking will allow new measurements of time-dependent statistical fields. Measurements in a vibrofluidized quasi-2D granular gas undergoing gravitational collapse will provide critical tests of how hydrodynamic approximations begin to fail. In addition two educational and outreach initiatives will be pursued. Upper level undergraduate courses in quantum and classical mechanics, emphasizing the active engagement of students in learning through experimental activities, will be developed at Wesleyan University. Through a partnership with PIMMS (Project to Increase Mastery of Mathematics and Science), the PI will train elementary teachers in urban school districts in mastering the content of the physical science units they teach to their students. This project is co-funded by the Division of Materials Research (Condensed Matter Physics) and the Division of Chemical Transport Systems (Particulate and Multiphase Processes).
The central outcome of this five year Faculty Early Career Development (CAREER) award was to allow the PI to build a firm foundation for a lifetime of leadership in integrating education and research. The research goals of this project were met for studies of both turbulent fluid flow and granular flow. In granular physics, we have studied the key role played by gravity in the collapse of a granular gas [1]. We have also developed very high resolution imaging techniques that have allowed detailed studies of granular shock waves and momentum transport in granular flows [2]. We have developed a new system for real-time compression of high speed video images [3] that has been adopted by several other research groups. We used this system to measure particle trajectories in turbulent fluid flow and to quantify the ways in which turbulent flows are universal (independent of how they are stirred) and the ways in which they depend on the details of the stirring [4,5]. We also explored the motion of particles that are carried by turbulence. When particles are large they average over the structure of turbulence and have accelerations smaller than the fluid that we showed how to measure and predict [6]. When particles are rod-shaped, they rotate and are aligned by the turbulence [7,8]. The study of particle motion in turbulent flow is a highly interdisciplinary field with many critical applications in geophysical flows (including climate science) and engineering flows. There has been a significant increase in research activity exploring particle motion in turbulence over the past decade, and this grant has positioned my research group to be a major contributor in years to come. This grant supported mentoring of 10 graduate students and 12 undergraduate students in research. The interactive engagement course for undergraduate quantum mechanics that was developed by the PI with support from this grant has been highly successful. One comment from the student evaluations summarizes it well: ‘… doing two experiments made this probably the best physics class I have taken in college. Doing quantum spectroscopy takes a subject that, while fun, can be very inaccessible and makes it seem so much more real’. With support from this grant, the PI has partnered with PIMMS (Project to Increase Mastery of Mathematics and Science) to provide professional development for K-12 educators in Connecticut. In a week long course and several workshops, the PI worked with an experienced educator to guide teachers in the use of exploration based science kits in their classrooms. [1] Reuben Son, John A. Perez, and Greg A Voth, "Experimental measurements of the collapse of a 2D granular gas under gravity." Physical Review E, 78, 041302 (2008). [2] John A. Perez, Samuel B. Kachuck and Greg A. Voth, "Visualization of Collisional Substructure in Granular Shock Waves." Physical Review E, 78, 041309 (2008). [3] King-Yeung Chan, Dominik Stich, and Greg A. Voth, "Real-time image compression for high-speed particle tracking." Review of Scientific Instruments, 78, 023704 (2007). [4] Daniel B. Blum, Surendra B. Kunwar, James Johnson, and Greg A. Voth, "Effects of nonuniversal large scales on conditional structure functions in turbulence" Physics of Fluids, 22, 015107 (2010). [5] Daniel B. Blum, Gregory P. Bewley, Eberhard Bodenschatz, Mathieu Gibert, Armann Gylfason, Laurent Mydlarski, Greg A. Voth, Haitao Xu, P. K. Yeung, "Signatures of non-universal large scales in conditional structure functions from various turbulent flows" New Journal of Physics 13, 113020 (2011). [6] Rachel D. Brown, Z. Warhaft, and Greg A. Voth, "Acceleration Statistics of Neutrally Buoyant Spherical Particles in Intense Turbulence." Physical Review Letters, 103, 194501 (2009). [7] Shima Parsa, Jeffrey S. Guasto, Monica Kishore, Nicholas T. Ouellette, J.P. Gollub, and Greg A. Voth ‘Rotation and alignment of rods in two-dimensional chaotic flow’, Physics of Fluids, 23, 043302 (2011). [8] Shima Parsa, Enrico Calzavarini, Federico Toschi, and Greg A. Voth, "Rotation rate of rods in turbulent fluid flow", Phys. Rev. Lett., 109, 134501 (2012).
