Current topics of interest include investigations of a broad class of problems where there is a competition between order and disorder, such as in mixing and segregation of granular matter or fluid mixing and, more generally, problems in the realm of complex systems involving tools such as agent-based models and network theory.

The interest in basic understanding of mixing lies in the ubiquity of mixing processes in technology and nature; examples are found in chemical, mechanical, and aeronautical engineering, but also in geophysics, physiology, oceanography, polymer engineering, and environmental sciences.

The work in granular dynamics involves a blend of theory, computations, and experimental work that reaches into applications. While important to a wide range of industries, our understanding of solid mixing and segregation is primitive. Some key questions we are currently addressing are: What features of mixing can be predicted computationally? What causes demixing and how it interplays with mixing? How can mixing be optimized?

R. Sturman, J.M. Ottino, and S. Wiggins, Mathematical Foundations of Mixing: The Linked Twist Map as a Paradigm in Applications Micro to Macro, Fluids to Solids, Cambridge University Press, Cambridge, England, 2006

J.M. Ottino, Engineering Complex Systems, Nature, 427, 399 (2004).

L.A.N. Amaral and J.M. Ottino, Complex Networks: Completing the framework for the study of complex systems, European Physics Journal, 38, 47-162 (2004).

L.A.N. Amaral and J.M. Ottino. Complex Systems and Networks Challenges and Opportunities for Chemical and Biological Engineering, Chemical Engineering Science, 59, 1653-1666 (2004).

S.J. Fiedor and J.M. Ottino, Mixing and segregation of granular matter: multi-lobe formation in time-periodic flows, J. Fluid Mech., 533, 223-236 (2005).

B.A. Socie, P. Umbanhowar, R.M. Lueptow, N. Jain, and J.M. Ottino, Creeping motion in granular flow, Phys. Rev. E, 71(3), 031304 (2005).

N.A. Pohlman, S.W Meier, R.M. Lueptow, and J.M. Ottino, Surface Velocity in Three-Dimensional Granular Tumblers, J. Fluid Mech. 560, 355 368 (2006).

J.M. Ottino, Granular Matter as a Window into Collective Systems far from Equilibrium, Complexity, and Scientific Prematurity, Chem. Eng. Sci., 61, 4165-4171 (2006).

S.J. Fiedor, P.B. Umbanhowar, and J.M. Ottino, Dynamics of axial segregation in granular slurries: Parallel experiments and influence of aspect ratio and periodic tilting, Phys. Rev. E, 73, 041303 (2006).

N.A. Pohlman, J.M. Ottino and R.M. Lueptow, End-wall effects in granular tumblers: From quasi-two-dimensional flow to three-dimensional flow," Physical Review E (Vol. 74, No. 3): Phys. Rev. E 74, 031305 (2006).

S.W. Meier, S.E. Cisar, R.M. Lueptow, and J.M. Ottino, Capturing patterns and symmetries in time-periodic granular flow using polydisperse particles, Phys. Rev. E., 74(3), Art No 031310, Sept. 2006.

B.L. Severson, J.M. Ottino, R.Q. Snurr, Analysis of lubrication failure using molecular simulation, Tribology Lett., 23(3), 253-260 (2006).

T. Arndt, A. Brucks, J.M. Ottino, and R.M Lueptow, Creeping granular motion under variable gravity levels, Phys, Rev, E. 74 (3), Art. No 031307, Part 1, Sept. 2006.

"Complex Systems," J.M. Ottino, AIChE J. 49, 292-299 (2003).

"Is a picture worth 1000 words?" J.M. Ottino, Nature 421, 474-476 (2003).

"Surface Flows of Granular Materials: Model and Experiments in Heap Formation," D.V. Khakhar, A.V. Orpe, P. Andresén, and J.M. Ottino, J. Fluid Mechanics, 441, 255-264 (2001).

"Surface Granular Flows: Two Related Examples," D.V. Khakhar, A.V. Orpe, and J.M. Ottino, Advances in Complex Systems, 4, 407-417 (2001).

"Chaotic Mixing in a Bounded Three Dimensional Flow," G.O. Fountain, D.V. Khakhar, I. Mezic, and J.M. Ottino, J. Fluid Mechanics, 147, 265-301, 2000.

"Chaotic Mixing in a Bounded Three Dimensional Flow," Fountain, G.O., Khakhar, D.V., Mezic, I., and Ottino, J.M., J. Fluid Mechanics, 147, 265-301, 2000.

"Mixing and Segregation of Granular Materials," Ottino, J.M. and Khakhar, D.V., Annual Review of Fluid Mechanics, 32, 55-91, 2000.

"The Art of Mixing with an Admixture of Art: Viewing Creativity through P.A. Danckwerts' Early Work (Danckwerts Memorial Lecture).," Ottino, J.M., Chem. Eng. Sci., 55, 2749-2765, 2000 A slightly different version of this article is reprinted also in Inst. of Chemical Engineers, 78(A), 871-880, 2000.

"Mixing of Granular Materials: A Test-Bed Dynamical System for Pattern Formation," Hill, K.M., Gilchrist, J.F., Khakhar, D.V., McCarthy, J.J. and , Intern. Jour. Bifurc. and Chaos, 9, 1467-1484, 1999 (cover article).

"Segregation-Driven Organization in Chaotic Granular Flows," Hill, K.M., Khakhar, D.V., Gilchrist, J.F., McCarthy, J. J. and Ottino, J.M., Proceedings of the National Academy of Sciences, Vol 96, Issue 21, pp. 11701-11706, October 1999.

"Chaotic Mixing of Granular Materials in 2D Tumbling Mixers" Khakhar, D.V., McCarthy, J.J., Gilchrist J.F. and Ottino, J.M, CHAOS 9 (1999): 195-205.

J.M. Ottino, The Kinematics of Mixing: Stretching, Chaos, and Transport, Cambridge University Press, Cambridge, England, 1989.