Browsing Complex Rheology and Biomechanics Lab (CRAB LAB) by Issue Date
Now showing items 1-20 of 37
-
Absence of inelastic collapse in a realistic three ball model
(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 ... -
Continuum-type stability balloon in oscillated granular layers
(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 ... -
Phase bubbles and spatiotemporal chaos in granular patterns
(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 ... -
Lattice dynamics and melting of a nonequilibrium pattern
(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 ... -
Kink-induced transport and segregation in oscillated granular layers
(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 ... -
Noise, coherent fluctuations, and the onset of order in an oscillated granular fluid
(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
(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 ... -
Dynamics of drag and force distributions for projectile impact in a granular medium
(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, ... -
Crucial role of sidewalls in velocity distributions in quasi-two-dimensional granular gases
(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
(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 ... -
Robotics in Scansorial Environments
(Georgia Institute of TechnologySociety of Photo-optical Instrumentation Engineers (SPIE), 2005) -
Stationary state volume fluctuations in a granular medium
(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 ... -
The RiSE Climbing Robot: Body and Leg Design
(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 ... -
Toward a dynamic climbing robot
(Georgia Institute of Technology, 2006)Simple mathematical models or ‘templates’ of locomotion have been effective tools in understanding how animals move and have inspired and guided the design of robots that emulate those behaviors. This paper describes a ... -
Signatures of glass formation in a fluidized bed of hard spheres
(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 ... -
Design of a Bio-inspired Dynamical Vertical Climbing Robot
(Georgia Institute of TechnologyMIT Press, 2008)This paper reviews a template for dynamical climbing originating in biology, explores its stability properties in a numerical model, and presents emperical data from a physical prototype as evidence of the feasibility of ... -
Scaling and Dynamics of Sphere and Disk Impact into Granular Media
(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 ... -
Integrating a Hierarchy of Simulation Tools for Legged Robot Locomotion
(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 ... -
Sensitive dependence of the motion of a legged robot on granular media
(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 ... -
March of the SandBots
(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 ...