Now showing items 14-33 of 37

    • 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 ...
    • Force and flow transition in plowed granular media 

      Gravish, Nick; Umbanhowar, Paul B.; Goldman, Daniel I. (Georgia Institute of TechnologyAmerican Physical Society, 2010-09-06)
      We use plate drag to study the response of granular media to localized forcing as a function of volume fractionϕ. A bifurcation in the force and flow occurs at the onset of dilatancy ϕ [subscript c]. Below ϕ [subscript ...
    • Granular impact and the critical packing state 

      Umbanhowar, Paul B.; Goldman, Daniel I. (Georgia Institute of TechnologyAmerican Physical Society, 2010-07-15)
      Impact dynamics during collisions of spheres with granular media reveal a pronounced and nontrivial dependence on volume fraction ϕ. Postimpact crater morphology identifies the critical packing state ϕcps, where sheared ...
    • Integrating a Hierarchy of Simulation Tools for Legged Robot Locomotion 

      Slatton, Andrew; Cohen, Daniel; Ding, Yang; Umbanhowar, Paul B.; Goldman, Daniel I.; Haynes, G. Clark; Komsuoglu, Haldun; Koditschek, Daniel E. (Georgia Institute of TechnologyInstitute of Electrical and Electronics Engineers, 2008-09)
      We are interested in the development of a variety of legged robot platforms intended for operation in unstructured outdoor terrain. In such settings, the traditions of rational engineering design, driven by analytically ...
    • 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 ...
    • 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 ...
    • 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 ...
    • March of the SandBots 

      Goldman, Daniel I.; Komsuoglu, Haldun; Koditschek, Daniel E. (Georgia Institute of TechnologyInstitute of Electrical and Electronics Engineers, 2009-04)
      Goldman at Georgia Tech, Koditschek and Komsuoglu at the University of Pennsylvania, in Philadelphia, and other collaborators - are hoping that by studying the zebra-tailed lizard and a menagerie of other desert-dwelling ...
    • 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 ...
    • 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 ...
    • Noise, coherent fluctuations, and the onset of order in an oscillated granular fluid 

      Goldman, Daniel I.; Swift, J. B.; Swinney, Harry L. (Georgia Institute of TechnologyAmerican Physical Society, 2004-04-30)
      We study fluctuations in a vertically oscillated layer of grains below the critical acceleration for the onset of ordered standing waves. As onset is approached, transient disordered waves with a characteristic length scale ...
    • 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 ...
    • 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 ...
    • The RiSE Climbing Robot: Body and Leg Design 

      Saunders, Aaron; Goldman, Daniel I.; Full, Robert J.; Buehler, Martin (Georgia Institute of TechnologySociety of Photo-optical Instrumentation Engineers (SPIE), 2006)
      The RiSE robot is a biologically inspired, six legged climbing robot, designed for general mobility in scansorial (vertical walls, horizontal ledges, ground level) environments. It exhibits ground reaction forces that are ...
    • Robotics in Scansorial Environments 

      Autumn, Kellar; Buehler, Martin; Cutkosky, Mark; Fearing, Ronald S.; Full, Robert J.; Goldman, Daniel I.; Groff, Richard; Provancher, William; Rizzi, Alfred E.; Saranli, Uluc; Saunders, Aaron; Koditschek, Daniel E. (Georgia Institute of TechnologySociety of Photo-optical Instrumentation Engineers (SPIE), 2005)
    • Scaling and Dynamics of Sphere and Disk Impact into Granular Media 

      Goldman, Daniel I.; Umbanhowar, Paul B. (Georgia Institute of TechnologyAmerican Physical Society, 2008-02-29)
      Direct measurements of the acceleration of spheres and disks impacting granular media reveal simple power law scalings along with complex dynamics which bear the signatures of both fluid and solid behavior. The penetration ...
    • 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 ...
    • Signatures of glass formation in a fluidized bed of hard spheres 

      Goldman, Daniel I.; Swinney, Harry L. (Georgia Institute of TechnologyAmerican Physical Society, 2006-04-14)
      We demonstrate that a fluidized bed of hard spheres during defluidization displays properties associated with formation of a glass. The final state is rate dependent, and as this state is approached, the bed exhibits ...
    • Stationary state volume fluctuations in a granular medium 

      Schroeter, Matthias; Goldman, Daniel I.; Swinney, Harry L. (Georgia Institute of TechnologyAmerican Physical Society, 2005-03-30)
      A statistical description of static granular material requires ergodic sampling of the phase space spanned by the different configurations of the particles. We periodically fluidize a column of glass beads and find that ...