Pine Research Group
research
Random Organization

Random Organization Simulation: Play movies, watch particles reorganize. Then read ...

Simulation movies showing random organization. Particles are randomly placed in a 2D rectangle. If the particle density is large enough, many of the particles will overlap. The particles are then sheared back an forth through a strain of γ0 as shown in the figure below. The movies above show the positions of the particles at the end of each shear cycle. Particles that collided in the previous cycle are given a small random displacement and colored red for easy identification. LEFT movie: Particles are sheared through a strain of γ0 =2 each cycle. By means of the random displacements, all the particles eventually find positions for which there are no collisions when the system is sheared. RIGHT movie: Particles are sheared through a strain of γ0 =2 each cycle. Particles never find positions for which there are no collisions but go to a steady state in which a finite fraction of particles continue to colloid.

Algorithm for random organization. System of particles are sheared through a strain of γ0 where strain is defined as the distance the top moves divided by the height of the system. Particles are displaced with the shear and are said to collide if they come within a distance d of each other (d is indicated by the diameter of the circles). Those that do collide are given a small random displacement (3rd frame) at the end of the cycle.

Random Organization

Random organization is a very general process by which physical driven systems far from equilibrium can organize themselves through random interactions. The model was developed by Paul Chaikin to help us understand a transition from irreversible to reversible behavior in sheared suspensions of non-Brownian particles (see Hydrodynamic Reversibility).