Campuses:

Motion of Complex Shaped Particle in Newtonian Fluid

Monday, September 27, 2004 - 11:00am - 11:50am
Keller 3-180
Masao Doi (University of Tokyo)
How a small particle suspended in a Newtonian fluid moves under an external force is a very classical problem of hydrodynamics, but seems to be attracting a resurgent interest in some recent technologies such as micro printing and micro electro mechanical systems. Detailed studies have been done for hydrodynamic problems such as how the mobility tensors depend on particle shape, but not much studies have been done for the statistical problems such as how the ensemble of complex shaped particles move in flow field. We have constructed a simulator which calculates the motion of rigid particles of general shape under external fields (force, torque and flow fields). Here we discuss two applications of the simulator, the sedimentation and the migration of complex shaped particles.

(1) Sedimentation: we discuss the sedimentation behavior of particles of general shape under gravity. The set of particles placed at the origin will disperse as they settle down. We shall show that the dispersion behavior is strongly dependent on the particle shape. We classify the types of the sedimentation behavior and discuss how they are related to particle shape.

(2) Separation: we discuss whether we can separate chiral particles (i.e., the particle themirror image of which cannot be superimposed on the original one by the operation of rotation) from its racemic mixture by using the difference in the migration velocity of the particle in a shear flow. Linear response theory and symmetry consideration indicates, that such separation is not possible. However, it can be shown that if strong shear flow is used , one can separate the right handed particle from the left handed particles.