Paul B. Umbanhowar Adjunct Professor Dept. of Mechanical Engineering Northwestern University 2145 Sheridan Road, Rm. B221 Evanston, IL 60208-3111, USA umbanhowar@northwestern.edu   BA, Carleton College (1987) MS, Boston University(1991) PhD, The University of Texas at Austin(1996)

Research: Granular materials; pattern formation; non-linear and non-equilibrium dynamics; locomotion on non-solid substrates

Professor Umbanhowar's research in granular materials examines the interaction of legged devices and animals with unconsolidated substrates; the dependence of drag force and penetration resistance on granular material state and intruder geometry and kinematics;  segregation, mixing, and flow in shaken, tumbled, fluidized, and stirred granular ensembles;  and pattern formation and its connection to continuum theories of discrete particulate systems.

Another related area of interest is motion control and self assembly/organization through vibrational manipulation of contact interactions mediated by friction and impact.

(clockwise from upper left) DEM simulations showing differences in impact dynamics between loose (left) and close (right) packed granular media. (upper right) SandBot walking on a bed of poppy seeds. (lower right) MR imaging of flow induced Reynolds dilatancy in a split-bottomed shear cell. (lower left) Oscillon (localized standing wave) in a layer of bronze beads.

In the classroom

Professor Umbanhowar has taught courses on classical, quantum, and statistical mechanics, thermodynamics, electrodynamics, and mechanical vibrations. His teaching emphasizes the development of physical intuition and the underlying interrelation of methodologies.

Selected publications

Thomas Vose, Paul Umbanhowar and Kevin Lynch. Friction-induced lines of attraction and repulsion for parts sliding on an oscillated plate. IEEE Transactions on Automation Science and Engineering, to appear.

Chen Li, Paul B. Umbanhowar, Haldun Komsuoglu, Daniel E. Koditschek and Daniel I. Goldman, Sensitive dependence of the motion of a legged robot on granular media. Proc. Natl. Acad. Sci., 106:3029, 2009.

Ken Sakaie, Dennis Fenistein, T.J. Carroll, Martin van Hecke and Paul Umbanhowar. MR imaging of Reynolds dilatancy in the bulk of smooth granular flows. Eurphys. Lett., 84:38001, 2008.

Paul Umbanhowar and Kevin M. Lynch. Optimal vibratory stick-slip transport. IEEE Transactions on Automation Science and Engineering, 5:537, 2008.

Daniel I. Goldman and Paul Umbanhowar. Scaling and dynamics of sphere and disk impact into granular media, Phys. Rev. E., 77:021308, 2008.

Ashley Smart, Paul Umbanhowar and Julio Ottino. Effects of self-organization on transport in granular matter: A network based approach. Europhys. Lett., 79:24002, 2007.

Paul B. Umbanhowar and Daniel I. Goldman. Low density fragile states in cohesive powders. Am. J. Phys., 74:720-721, 2006.

Phil N. Segrè, Fun Liu, Paul Umbanhowar and David A. Weitz. Effective gravitational temperature for sedimentation. Nature, 409:594-597, 2001.

Paul B. Umbanhowar, Francisco Melo and Harry L. Swinney. Localized excitations in a vertically vibrated granular layer. Nature, 382:793-796, 1996.