Dynamical simulations of sedimentation

Conference · Sun Dec 01 04:00:00 EST 1991

OSTI ID:10157506

Ladd, A J.C.

In previous work I have developed a numerical technique for computing the hydrodynamic interactions between suspended solid spheres [1-31]. By averaging appropriate elements of the mobility matrix over random (non-overlapping) configurations of hard spheres, the high-frequency or short-time hydrodynamic transport coefficients can be calculated; the results are in excellent agreement with experiment [3]. During sedimentation. microstructure rearrangements take place; thus the steady-state sedimentation velocity can differ from its initial value. Moreover the suspension does not sediment as a homogeneous unit; rather there is a substantial dispersion of the particle velocities due to microscopic inhomogeneities in panicle position. In this paper I present results arising from the dynamical simulation of sedimenting spheres; I limit myself to results at a single packing fraction, {phi} = 0.05, to compare with the experimental results of Ham and Homsy [5]. The methodology is a straightforward development of that described in Refs. [1-3] for creeping flow hydrodynamic interactions. Given the location and the force (gravity) on each particle. the velocity and angular velocity are calculated. In this work it has been assumed that the force density on the surface of each sphere, arising from its interactions with the fluid, can be represented by a force, a torque and a stresslet.

• Research Organization: Lawrence Livermore National Lab., CA (United States)
• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 10157506
• Report Number(s): UCRL-JC--109143; CONF-9110369--3; ON: DE93013838
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
420400
FLUID MECHANICS
HEAT TRANSFER AND FLUID FLOW
INTERACTIONS
PARTICLE SIZE
SEDIMENTATION
SIMULATION
SPHERES
SUSPENSIONS