Levich Institute Seminar Announcement, 02/10/2004

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Tuesday, 02/10/2004
4:00 PM
Steinman Hall, Room #312
(Chemical Engineering Conference Room)

Professor Eric Shaqfeh
Stanford University
Department of Chemical Engineering


"Turbulent Drag Reduction Mechanisms by Fiber and Polymer Additives as Determined from Large Scale Simulation "

(This is a CCNY/Columbia NSF-IGERT Soft Materials seminar)

ABSTRACT

Since the original observations of drag reduction by Toms (1948), the molecular mechanisms by which the drag in a turbulent channel flow is reduced have been the subject of a great deal of theory. The talk will focus on the mechanisms of turbulent drag reduction by polymer and fiber additives as elucidated from large scale numerical simulation of both turbulent channel flow and developing boundary layer flow. In particular, the precise mechanisms of energy transport in and around the streamwise vortices and associated velocity "streaks" will be examined via a statistical framework. We examine the following questions in detail:
  1. What types of flows create large polymer and fiber stresses in wall-bound turbulent flows and are these the same for both additive types?
  2. What affects do intramolecular hydrodynamic interactions have on the polymer dynamics and do these affect the polymer stress production as well as drag reduction?
  3. In what types of flows is energy stored in polymer configuration and in which types is it released? How does this effect the near-wall structures?
The talk will focus on both the universal elements as well as the differences in the simulated drag reduction mechanisms of polymers and fibers. Moreover, we demonstrate that the so-called HDR (High Drag Reduction) state as well as MDR are turbulent states which are maintained by the release of stored energy in the polymers: therefore polymer stressed maintain this turbulence. These states do not appear to be attainable with fibers alone. Three new algorithms are introduced to accomplish the goals of this study: a fully parallelized BD code for multi-bead spring chains including the fully implicit configuration time-stepping developed by Somasi etal. (2002), a semi- (and fully) implicit finite difference code for the DNS using the FENE-P and FENE-HI models, and a semi-implicit fiber stress code that includes the extra stresses due to included Brownian fibers. The advantages of each of these codes will be discussed in light of our ultimate objectives.

(With Yves Dubief, Vince Terrapon, John Paschkewitz, Chris White, Vijay Somandepalli, Sanjiva Lele, Parviz Moin, and Godfrey Mungal)


BRIEF ACADEMIC/EMPLOYMENT HISTORY:

Eric Shaqfeh is a native of Schuylkill Haven, Pennsylvania. He received a B.S.E. summa cum laude from Princeton University in 1981 and a Ph.D. from Stanford University in 1986, the latter under the mentorship of Andreas Acrivos. He was then awarded a NATO Postdoctoral Fellowship for postdoctoral studies in the Department of Applied Mathematics and Theoretical Physics at Cambridge University, where he collaborated with John Hinch and George Batchelor. Eric was a Member of Technical Staff at AT&T Bell Laboratories from 1987 to 1990, after which he joined the Stanford Chemical Engineering Department as an Assistant Professor. He is currently Professor of Chemical Engineering and Mechanical Engineering at Stanford, and he serves as Associate Chair of Chemical Engineering. He is presently on sabbatical leave at the University of Wisconsin as the Hougen Professor of Chemical Engineering. Eric is widely known for seminal contributions, both experimental and theoretical, in non-Newtonian fluid mechanics, nonequilibrium polymer statistical dynamics, suspension mechanics (particularly of fiber suspensions and composites), and diffusion/reaction in plasma etching processes. His honors include the Francois N. Frenkiel Award of the American Physical Society (1989), the National Science Foundation Presidential Young Investigator Award (1990), the David and Lucile Packard Fellowship in Science and Engineering (1991), the Camile and Henry Dreyfus Teacher-Scholar Award (1994), the W.M. Keck Foundation Engineering Teaching Excellence Award (1994), and the Curtis W. McGraw Award of the American Society for Engineering Education (1998). He was elected a Fellow of the American Physical Society in 2000.