Granular flow: Numerical simulation of dry granular flows and calculation of hydrodynamic interactions in suspensions: Period of performance: October 1, 1988--May 30, 1989

Conference · Sat Jul 01 04:00:00 EDT 1989

OSTI ID:5840459

Ladd, A J.C.; Walton, O R

Research emphasized two major topics: determination of the flow behavior of rapidly shearing dry granular solids and calculation of hydrodynamics forces in creeping flows of suspensions of spherical particles. Discrete particle computer models that calculate the motion of each inelastic, frictional particle in large assemblies were applied to the simulation of dry granular flows. A hard sphere model, employing instantaneous collisions and straight line trajectories between collisions, was used to perform binary mixture calculations with size ratios from 1 to 4. These simulations showed a stronger sample size dependence than previously recognized and qualitatively confirmed earlier results that stresses in shearing mixtures with large size ratios are lower than predicted by current theories. As part of the study of dry granular flows we also added new boundary conditions to the models, translated them to standard Fortran 77 for portability and continued existing collaborative efforts and established new collaborative research agreements with various University researchers. The suspension modeling portion of this research emphasized development of new accurate and efficient numerical schemes for calculating hydrodynamic interactions in suspensions of spherical particles. The method is based on a multipole moment expansion of the induced force density acting on the fluid at the surface of each particle. The convergence of the multipole expansion has been improved by including the short-range lubrication forces explicitly. Numerical results for the viscosity, diffusion constant, sedimentation velocity, and permeability were obtained and serve to illustrate the various stages of development of the method and to assess their effectiveness in representing the hydrodynamic interactions. 16 refs., 6 figs.

• Research Organization: Lawrence Livermore National Lab., CA (USA)
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 5840459
• Report Number(s): UCRL-101605; CONF-8905209-1; ON: DE89017544
• Country of Publication: United States
• Language: English

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