- Professor - Chemical Engineering
- Professor - Mechanical Engineering
- Professor - Institute of Computational and Mathematical Engineering
- Ph. D., Stanford University, 1986
Major Honors and Awards
- 1991-1996 David and Lucile Packard Fellow in Science and Engineering
- 1998 ASEE Curtis W. McGraw Research Award
- 2000 Fellow of the American Physical Society
- 2001 Van Ness Lectureship, Department of Chemical Engineering, RPI
- 2003 Stanley Corrsin Lectureship, The Johns Hopkins University
- 2004 Hougen Professor, Department of Chemical Engineering, University of Wisconsin, Madison
- 2006 Associate Editor, Physics of Fluids
Research Area
Transport, Rheology, and Complex Fluids
Transport Mechanics of Complex Fluids
Our research program includes the study of different areas associated with transport in complex fluids including: a) the occurrence of purely elastic instabilities in polymer flows, b) the micro-dynamics of polymer molecules, including DNA, in nonequilibrium transport, c) the flow behavior of fiber suspensions, d) the general microfluidic flow behavior of complex fluids and, most recently, e) the stability of compressible boundary layer flows. Our approach in these areas includes developing large scale simulations (including both Brownian dynamics and continuum simulation) of poorly understood phenomena and then couple these to detailed experiments to elucidate the important physics in a variety of processes.
The Dynamics of Suspensions of Anisotropic and Deformable Particles in Sedimentation and in Microfluidic Flows
Collaboration with Eric Darve and Juan Santiago, Mechanical Engineering: Chemical Engineering Students: Anders Berliner and Brendan Hoffmann
For more than a decade, our group has examined the dynamics of nonBrownian fiber suspensions noting that the flow dynamics under all types of situations is qualitatively different than that found in suspensions of spheres. The simplest difference comes in the effect of hydrodynamic interactions where a given high aspect ratio fiber can interact with many of its neighbors before it ever interacts with its opposite end (!). Such semi-dilute fiber suspensions have properties which are dramatically different than their Newtonian suspending fluid even at remarkably small volume fraction. A second profound effect in fiber suspensions is associated with the mobility or drag coffiecient depending on orientation for fibers, and thus in sedimentation, fibers move rapidly in directions perpendicular as well as parallel to gravity. The consequence of this for a sedimenting suspension of fibers is that the suspension does not remain homogeneous but spontaneously forms "clumps" or "packets" which settle more quickly than an isolated fiber. We have discovered by simulation and theory, as well as by detailed experiment, that there is a region of particle concentration where the average sediment velocity is actually larger than the isolated particle rate. This finding brings new meaning to the phrase "hindered settling function"! This sedimentation velocity in suspension is therefore critically dependent on the "clumps" which form in the suspension. In new work, we have shown that this instability is generic to all separation processes involving deformable and orientable particles. In microfluidic applications, the induced electro-osmotic flows around the orientable particles creates new effects on this instability that we are examining in the context of simulating the operation of micro-barcode readers in collaboration with Eric Darve and Juan Santiago.
DNA Dynamics in Mixed Flows and in Micro- and Macro-Devices
(Funded by the Center of Polymer Interfaces and Molecular Assemblages, CPIMA, NSF Chemical, Biological and Thermal Sciences Division, NIH as well as the Army High Performance Computing Resaearch Center (AHPCRC); Students: Ajey Dambal, Chris Lueth, Brendan Hoffmann and Shikha Somani)
The dynamics of DNA, as both a probe for polymer dynamics in flow and as a research area of great importance to industries associated with biosensors and lab-on-a-chip devices, has been an ongoing theme in our research group for more than seven years. The research begins with the development of detailed Brownian dynamic models for DNA dynamics in a variety of well-characterized flow fields which are validated with single molecule flourescence microscopy originating in the Chu group. This combination has allowed the description of new physical principles governing these dynamics under highly nonequilibrium conditions, including the tumbling dynamics and fluctuation dynamics of molecules in a wide range of planar flows with varying ratios of strain and vorticity. These flows designated as "mixed" flows span the behavior from purely vortical flow to purely straining motion. In purely straining flows, we have now demonstrated that the coil-stretch transition is hysteretic with two kinetically separate bistable states simultaneously existing. The dynamics is also interesting near the "critical point" known as simple shear flow where the straining and vorticity are exactly balanced. For flows near this point the conformational "phase transition" is associated with large fluctuations that can be examined in a detailed manner both computationally and experimentally. Finally, in our latest work, we are moving to examine fluorescently decorated synthetic polymers and entangle polymer systems as well.
Our materials center known as CPIMA is focussed on the interfacial properties of polymers as well as their interfacial dynamics. Our developing DNA model has thus been applied to understand new DNA microdevices including post arrays for separation, and tmost recently, the separation of DNA in nanochannels.. Simulating these nonequilibrium processes where the statistical mechanics of unbound molecules is not applicable, allows for the understanding of the new important physical principles that govern these processes. Three primary examples we have examined include "hairpin" dynamics associated with the unravelling of chains around posts as they interact. These dynamics are critical to understanding the relative mobilities of molecules as they are passed through post arrays and this mobility difference can allow for separation under certain conditions..A second interesting piece of physics is that associated with the change in nonequilibrium chain dynamics when a polymer is constrained to a gap of thickness comparable to its radius of gyration or tethered near a stagnation point on a solid surface. The latter can create conformation hysteresis of a wholly new kind which we examine again via detailed simulation and experiment. Finally, the dynamics of DNA electrically driven through nanochannels includes the electormigration of the molecules as they interact with the charged walls as well as the electrophoretic and electro-osmotic driving forces down the channel. Ultimately the average mobility of the molecules depends on the complex interplay of these forces, which we are in a unique position to examine via large scale simulation.
A Molecular Simulation of Turbulent Drag Reduction by Flexible Polymers and/or Fibers
(Funded by AHPCRC; joint with Gianluca Iaccarino;; Mechanical Engineering and the Center for Turbulence Research, Stanford University: Students: David Richter)
In a broad project that combines all the expertise in the group, we have forged a collaboration with the Center for Turbulence Research to develop a molecular simulation of turbulent drag reduction including the effects of a number of different added micro-elements (e.g. flexible polymers and/or rigid fibers). Note that drag reduction is a 50 year old problem associated with originally with the name Thoms as the Thoms phenomena, where the addition of even very small (i.e. 5 ppm) of polymeric material can cause the reduction of turbulent drag by 80% in fully developed boundary layer and channel flows. The origins of this reduction at a molecular level are still the subject of heated debate. However, our research using a combination of Brownian dynamics simulations and coupled continuum solver (the so-called micro-macro method) allows for a direct numerical simulation of the phenomena using realistic molecular models that have been benchmarked in our ongoing research program associated with developing Brownian dynamic simulations of model polymers. Note in this context, that we have now developed large scale simulation of drag reduction in external flows, i.e. turbulent boundary layers and demonstrated that polymers both absorb and release energy from the turbulence. The release of energy, at very large levels of drag reduction, is responsible for sustaining the turbulent state itself. We have recently extended our simulation capability to be able to examine large scale flows including polymer drag reduction on the surfaces of hydro-foils and ship hulls via developing one of the first Reynolds Averaged Navier Stokes (RANS) models for drag reduction that faithfully captures the physics in our more fine-grained computer simulations.
Transition to Turbulence in Hypersonic Flows over Rough Surfaces
(Funded by NASA; joint with Gianluca Iaccarino;; Mechanical Engineering and the Center for Turbulence Research, Stanford University: Student: Nerses Ohanyan)
Space vehicles which re-enter the earth’s atmosphere do so at values of the Mach number in excess of 5-10. Small imperfections in a heat shield on these capsules can cause the compressible boundary layer to become turbulent, increasing the heat transfer my orders of magnitude and ultimately creating large ablation of the shields. The mechanism of transition in these situations is not understood at a fundamental level and is a classic problem in linear and nonlinear stability of boundary layer flows. Ablation itself can cause these imperfections and the outgassing created by an ablating surface may indeed make this transition more problematic. Again no control schemes or re-engineering of heat shields is possible without a fundamental understanding of the mechanisms. Here we combine large compressible flow calculations with linear and nonlinear stability analysis to predict the mechanisms of transition in boundary layer flows past small roughness elements at high Mach numbers.
Representative Recent Publications
1. Homan, B., E.S.G. Shaqfeh, "The Dynamics of the Coil-Stretch Transition for Long,Flexible Polymers in Planar Mixed Flows", J. Rheol. 51 , Issue 5, pp. 947-969 (2007) (see also Virtual Journal of Biological Physics Research September 1, 2007)
2. Lee, J.S., E.S.G. Shaqfeh, S.J. Muller, "Dynamics of DNA tumbling in shear to rotational mixed ows: Pathways and periods", Phys. Rev. E 75 , 040802 (2007) (see also Virtual. Journal of Biological Physics Research May 1, 2007)
3. Beck, V.A. and E.S.G. Shaqfeh, "Ergodicity-Breaking and the Unravelling Dynamics of a Polymer in Linear and NonLinear Extensional Flows", J. Rheol. 51(3), pp. 561-574 May/June (2007)
4. Teixeira, R., A.K. Dambal, D.H. Richter, E.S.G. Shaqfeh, and S. Chu, "The Individu-alistic Dynamics of Entangled DNA in Solution", Macromolecules , 40 (7) pp. 2461-2476 (2007)
5. Teclemariam N.P., V.A. Beck, E.S.G. Shaqfeh, S.J. Muller, "Dynamics of DNA polymers in post arrays: Comparison of single molecule experiments and simulations", Macro- molecules 40 (7) pp. 3848-3859 (2007)
6. Saintillan, D., E.S.G. Shaqfeh, E. Darve, "The eect of stratication on the wavenumber selection in the instability of sedimenting spheroids", Phys. of Fluids. 18 121503, (2006) Dimitropoulos C., Y. DuBief, E.S.G. Shaqfeh, P. Moin, "Direct numerical simulation of polymer-induced drag reduction in turbulent boundary layer ow of inhomogeneous polymer solutions", J. Fluid Mech. 566 pp. 153-162 (2006)
7. Saintillan, D., E. Darve, E.S.G. Shaqfeh, "Hydrodynamic interactions in the induced- charge electrophoresis of colloidal rod dispersions", J. Fluid Mech. 563 pp. 223-259 (2006)
8.Saintillan, D., E.S.G. Shaqfeh, E. Darve, "Stabilization of a suspension of sedimenting rods by induced-charge electrophoresis", Phys. Fluids 18 , 121701 (2006)
9. Beck, V.A. and E.S.G. Shaqfeh, "Ergodicity-Breaking and Conformational Hysteresis in Polymer Dynamics Near a Surface Stagnation Point", J. Chem Phys. 124 , 094902 (2006)
10. Beck, V.A. and E.S.G. Shaqfeh, "Ergodicity-Breaking and Conformational Hysteresis in Polymer Dynamics Near a Surface Stagnation Point", J. Chem Phys. 124 , 094902 (2006)
11. Saintillan D., E.S.G. Shaqfeh, E. Darve "Eect of exibility on the shear-induced mi-gration of polymers in parabolic channel ow", J. Fluid Mech. 557 (1) pp. 297-306 (2006)
12. Saintillan D., E.S.G. Shaqfeh, E. Darve, "The growth of concentration fluctuations in dilute suspensions of orientable or deformable particles under sedimentation'', J. Fluid Mech. 537, 347 (2006)
13.Beck, V.A. and E.S.G. Shaqfeh, "Ergodicity-Breaking and Conformational Hysteresis in Polymer Dynamics Near a Surface Stagnation Point'', J. Chem Phys. 124, 094902 (2006)
14. Saintillan, D., E. Darve, E.S.G. Shaqfeh, , "Hydrodynamic interactions in the induced-charge electrophoresis of colloidal rod dispersions'', J. Fluid Mech. 536 pp. 223-259 (2006)
15. Dimitropoulos C.D., Y. Dubief, E.S.G. Shaqfeh, P. Moin, S.K. Lele, "Direct numerical simulation of polymer-induced drag reduction in turbulent boundary layer flow'', Phys. Fluids. 17, 011705 (2005)
16. Shaqfeh, E.S.G, "The Dynamics of Single-Molecule DNA in Flow'', J. NonNewtonian Fluid Mechanics 130, pp. 1-28 (2005)
17. Schroeder, C., R. Teixeira, E.S.G. Shaqfeh, and S.Chu, "Characteristic periodic motion of polymers in shear flow'', Phys. Rev. Lett. 95, 018301 (2005)
18. Bhatara, G., E.S.G. Shaqfeh, B. Khomami, "The influence of polymer concentration and chain architecture on free surface displacement flows of polymeric fluids'', J. Rheology 49(5) pp. 929-962 (2005)
19. Paschkewitz J, Y. Dubief, E.S.G. Shaqfeh, "The dynamic mechanisms for turbulent drag reduction using rigid bers based on Lagrangian conditional statistics", Phys. Fluids.17 063102, (2005)
20. Teixeira, R., H.P. Babcock, E.S.G. Shaqfeh, and S. Chu, "Shear thinning and tumbling dynamics of single polymers in the ow-gradient plane", Macromolecules , 38 (2), pp.581-592 (2005) (also see Macromolecules , cover, April 5,2005 38 (7))
21. Schroeder, C., R. Teixeira, E.S.G. Shaqfeh, and S.Chu, "Characteristic periodic motion of polymers in shear ow", Phys. Rev. Lett. 95 , 018301 (2005)
22. Schroeder, C., R. Teixeira, E.S.G. Shaqfeh, and S.Chu, "Dynamics of DNA in the ow- gradient plane of steady shear ow: Observations and simulations", Macromolecules , 38 (5) 1967-1978 (2005)
23. Shaqfeh, E.S.G, "The Dynamics of Single-Molecule DNA in Flow", J. NonNewtonian Fluid Mechanics 130 , pp. 1-28 (2005)
24. Schroeder, C., E.S.G. Shaqfeh, and S.Chu, "The Eect of Hydrodynamic Interactions on the Dynamics of DNA in Extensional Flow: Simulation and Single Molecule Experiment", Macromolecules , 37 , pp. 9242-9256 (2004)
25. Paschkewitz, J.S., Y. Dubief, E.S.G. Shaqfeh and P. Moin, "Numerical simulation of turbulent drag reduction using rigid fibres'', J. Fluid Mech. 518 pp. 281-317 (2004)
26. Terrapon, V.E., Y. DuBief, P. Moin, E.S.G. Shaqfeh, and S.K. Lele, "Simulated polymer stretch in a turbulent flow using Brownian dynamics'', J. Fluid Mech. 504, pp. 61-71 (2004)
27. Dubief, Y.,C.M. White, V.E. Terrapon, E.S.G. Shaqfeh, P. Moin, and S. K. Lele, "On the coherent drag reducing and turbulence enhancing behavior of polymers in wall flows'', J. Fluid Mech 514, pp. 271-280 (2004)
28. Schroeder, C., E.S.G. Shaqfeh, and S.Chu, "The Effect of Hydrodynamic Interactions on the Dynamics of DNA in Extensional Flow: Simulation and Single Molecule Experiment'', Macromolecules, 37, pp. 9242-9256 (2004)
29. Schroeder, C.M., H. Babcock, E.S.G. Shaqfeh, S. Chu, "Observation of Polymer Configuration Hysteresis in Extensional Flow'', Science , 9/12/2003, Vol. 301, Issue 5639 pp. 1515-1519
Ph.D. Students - Undergraduate Institutions
- Chris Lueth -- Univ. of Minnesota
- Ajey Dambal -- Washington University at St. Louis
- Brendan Hoffman -- University of Maryland
- Shikha Somani - Indian Institute of Technology, Bombay
- Anders Berliner - Case Western Reserve University
- David Richter - (Mechanical Engineering) University of Massachusetts
- Nerses Ohanyan - (Mechanincal Engineering) University of Southern California
