Our research addresses problems in nonequilibrium systems that involve interaction of physical and biological matter with complex materials (like granular media) that typically flow when stressed. For example, how do organisms like lizards, crabs, and cockroaches generate appropropriate musculoskeletal dynamics to scurry rapidly over substrates like sand, bark, leaves, and grass.

The study of novel biological and physical interactions with complex media can also lead to the discovery of principles that govern the physics of the media. Our approach is to integrate laboratory and field studies of organism biomechanics with systematic laboratory studies of physics of the substrates, as well as to create mathematical and physical (robot) models of both organism and substrate.

Recent Submissions

  • Effect of Volume Fraction on Granular Aavalanche Dynamics 

    Gravish, Nick; Goldman, Daniel I. (Georgia Institute of TechnologyAmerican Physical Society, 2014)
    We study the evolution and failure of a granular slope as a function of prepared volume fraction, φ0. We rotated an initially horizontal layer of granular material (0.3-mm-diam glass spheres) to a 45◦ angle while we monitor ...
  • The Effectiveness of Resistive Force Theory in Granular Locomotion 

    Zhang, Tingnan; Goldman, Daniel I. (Georgia Institute of TechnologyAmerican Institute of Physics, 2014)
    Resistive force theory (RFT) is often used to analyze the movement of microscopic organisms swimming in fluids. In RFT, a body is partitioned into infinitesimal segments, each of which generates thrust and experiences ...
  • Colloquium: Biophysical principles of undulatory self-propulsion in granular media 

    Goldman, Daniel I. (Georgia Institute of Technology, 2014)
    Biological locomotion, movement within environments through self-deformation, encompasses a range of time and length scales in an organism. These include the electrophysiology of the nervous system, the dynamics of muscle ...
  • Force and flow at the onset of drag in plowed granular media 

    Gravish, Nick; Umbanhowar, Paul B.; Goldman, Daniel I. (Georgia Institute of TechnologyAmerican Physical Society, 2014)
    We study the transient drag force F[subscript D] on a localized intruder in a granular medium composed of spherical glass particles. A flat plate is translated horizontally from rest through the granular medium to observe ...
  • Multi-functional foot use during running in the zebra-tailed lizard (Callisaurus draconoides) 

    Li, Chen; Hsieh, S. Tonia; Goldman, Daniel I. (Georgia Institute of TechnologyCompany of Biologists, 2012-05)
    A diversity of animals that run on solid, level, flat, non-slip surfaces appear to bounce on their legs; elastic elements in the limbs can store and return energy during each step. The mechanics and energetics of running ...
  • A terradynamics of legged locomotion on granular media 

    Li, Chen; Zhang, Tingnan; Goldman, Daniel I. (Georgia Institute of TechnologyAmerican Association for the Advancement of Science, 2013-03-22)
    The theories of aero- and hydrodynamics predict animal movement and device design in air and water through the computation of lift, drag, and thrust forces. Although models of terrestrial legged locomotion have focused on ...
  • Sensitive dependence of the motion of a legged robot on granular media 

    Li, Chen; Umbanhowar, Paul B.; Komsuoglu, Haldun; Koditschek, Daniel E.; Goldman, Daniel I. (Georgia Institute of TechnologyNational Academy of Sciences, 2009-03-03)
    Legged locomotion on flowing ground (e.g., granular media) is unlike locomotion on hard ground because feet experience both solid- and fluid-like forces during surface penetration. Recent bioinspired legged robots display ...
  • The Effect of limb kinematics on the speed of a legged robot on granular media 

    Li, Chen; Umbanhowar, Paul B.; Komsuoglu, | Haldun; Goldman, Daniel I. (Georgia Institute of TechnologySociety for Experimental Mechanics, 2010-04-22)
    Achieving effective locomotion on diverse terrestrial substrates can require subtle changes of limb kinematics. Biologically inspired legged robots (physical models of organisms) have shown impressive mobility on hard ...
  • Walking and running on yielding and fluidizing ground 

    Qian, Feifei; Zhang, Tingnan; Li, Chen; Masarati, Pierangelo; Birkmeyer, Paul; Pullin, Andrew; Hoover, Aaron; Fearing, Ronald S.; Golman, Daniel I. (Georgia Institute of Technology, 2012-07)
    We study the detailed locomotor mechanics of a small, lightweight robot (DynaRoACH, 10 cm, 25 g) which can move on a granular substrate of closely packed 3 mm diameter glass particles at speeds up to 50 cm/s (5 body ...
  • Lift-off dynamics in a simple jumping robot 

    Aguilar, Jeffrey; Lesov, Alex; Wiesenfeld, Kurt; Goldman, Daniel I. (Georgia Institute of TechnologyAmerican Physical Society, 2012-10-26)
    We study vertical jumping in a simple robot comprising an actuated mass-spring arrangement. The actuator frequency and phase are systematically varied to find optimal performance. Optimal jumps occur above and below (but ...
  • Mechanics of undulatory swimming in a frictional fluid 

    Ding, Yang; Sharpe, Sarah S.; Masse, Andrew; Goldman, Daniel I. (Georgia Institute of TechnologyPublic Library of Science, 2012-12)
    The sandfish lizard (Scincus scincus) swims within granular media (sand) using axial body undulations to propel itself without the use of limbs. In previous work we predicted average swimming speed by developing a numerical ...
  • Continuum-type stability balloon in oscillated granular layers 

    De Bruyn, John R.; Bizon, C.; Shattuck, M. D.; Goldman, Daniel I.; Swift, J. B.; Swinney, Harry L. (Georgia Institute of TechnologyAmerican Physical Society, 1998-08-17)
    The stability of convection rolls in a fluid heated from below is limited by secondary instabilities, including the skew-varicose and crossroll instabilities. We observe a stability boundary defined by these same instabilities ...
  • Kink-induced transport and segregation in oscillated granular layers 

    Moon, Sung Joon; Goldman, Daniel I.; Swift, J. B.; Swinney, Harry L. (Georgia Institute of TechnologyAmerican Physical Society, 2003-09-26)
    We use experiments and molecular dynamics simulations of vertically oscillated granular layers to study horizontal particle segregation induced by a kink (a boundary between domains oscillating out of phase). Counterrotating ...
  • Lattice dynamics and melting of a nonequilibrium pattern 

    Goldman, Daniel I.; Shattuck, M. D.; Moon, Sung Joon; Swift, J. B.; Swinney, Harry L. (Georgia Institute of TechnologyAmerican Physical Society, 2003-03-14)
    We present a new description of nonequilibrium square patterns as a harmonically coupled crystal lattice. In a vertically oscillating granular layer, different transverse normal modes of the granular square-lattice pattern ...
  • Dynamics of drag and force distributions for projectile impact in a granular medium 

    Ciamarra, Massimo Pica; Lara, Antonio H.; Lee, Andrew T.; Goldman, Daniel I.; Vishik, Inna; Swinney, Harry L. (Georgia Institute of TechnologyAmerican Physical Society, 2004-05-14)
    Our experiments and molecular dynamics simulations on a projectile penetrating a two-dimensional granular medium reveal that the mean deceleration of the projectile is constant and proportional to the impact velocity. Thus, ...
  • Phase bubbles and spatiotemporal chaos in granular patterns 

    Moon, Sung Joon; Shattuck, M. D.; Bizon, C.; Goldman, Daniel I.; Swift, J. B.; Swinney, Harry L. (Georgia Institute of TechnologyAmerican Physical Society, 2001-12-04)
    We use inelastic hard sphere molecular dynamics simulations and laboratory experiments to study patterns in vertically oscillated granular layers. The simulations and experiments reveal that phase bubbles spontaneously ...
  • Absence of inelastic collapse in a realistic three ball model 

    Goldman, Daniel I.; Shattuck, M. D.; Bizon, C.; McCormick, W. D.; Swift, J. B.; Swinney, Harry L. (Georgia Institute of TechnologyAmerican Physical Society, 1998-04)
    Inelastic collapse, the process in which a number of partially inelastic balls dissipate their energy through an infinite number of collisions in a finite amount of time, is studied for three balls on an infinite line and ...
  • Persistent holes in a fluid 

    Merkt, Florian S.; Deegan, Robert D.; Goldman, Daniel I.; Rericha, Erin C.; Swinney, Harry L. (Georgia Institute of TechnologyAmerican Physical Society, 2004-05-07)
    We observe stable holes in a vertically oscillated 0.5 cm deep aqueous suspension of cornstarch. Holes appear only if a finite perturbation is applied to the layer for accelerations α above 10g. Holes are circular and ...
  • Crucial role of sidewalls in velocity distributions in quasi-two-dimensional granular gases 

    van Zon, J. S.; Kreft, J.; Goldman, Daniel I.; Miracle, D.; Swift, J. B.; Swinney, Harry L. (Georgia Institute of TechnologyAmerican Physical Society, 2004-10-19)
    Our experiments and three-dimensional molecular dynamics simulations of particles confined to a vertical monolayer by closely spaced frictional walls (sidewalls) yield velocity distributions with non-Gaussian tails and a ...
  • Mach cone in a shallow granular fluid 

    Heil, Patrick; Rericha, Erin C.; Goldman, Daniel I.; Swinney, Harry L. (Georgia Institute of TechnologyAmerican Physical Society, 2004-12-23)
    We study the V-shaped wake (Mach cone) formed by a cylindrical rod moving through a thin, vertically vibrated granular layer. The wake, analogous to a shock (hydraulic jump) in shallow water, appears for rod velocities vR ...

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