Measurement of the full shearinduced selfdiffusion tensor of noncolloidal suspensions
Abstract
The full diffusion tensor of shearinduced selfdiffusion has been measured experimentally for the first time. In addition to the wellknown components in the velocity gradient, D_{yy}, and vorticity direction, D_{zz}, the coefficients D_{xx} and D_{xy} have been determined for concentrated suspensions of noncolloidal hard spheres as a function of particle volume fraction. Owing to the shearinduced nature of the phenomenon, these four coefficients are the only nonzero elements of the diffusion tensor. The newly determined diffusion quantities have been obtained by extending our correlation based technique [J. Fluid Mech. 375, 297 (1998); Phys. Rev. E 63, 021403 (2001)] with a method to subtract convective displacements due to the shear flow. The diffusion in the velocity direction, D_{xx}, is almost an order of magnitude larger than the other components and the only nonzero offdiagonal component, D_{xy}, is negative and small compared to the diagonal components of the diffusion tensor. In principle the applied technique is also feasible for measuring other anisotropic diffusion mechanisms, e.g., Brownian diffusion in steady shear flow.
 Publication:

Journal of Chemical Physics
 Pub Date:
 June 2002
 DOI:
 10.1063/1.1478770
 Bibcode:
 2002JChPh.11610529B
 Keywords:

 suspensions;
 selfdiffusion;
 velocity;
 shear flow;
 Brownian motion;
 multiphase flow;
 Brownian Movements;
 Diffusion;
 Multiphase Flow;
 Shear Flow;
 Suspensions;
 Velocity;
 66.10.Cb;
 82.70.Kj;
 83.50.Ax;
 83.80.Hj;
 47.55.Kf;
 SolidState Physics;
 Diffusion and thermal diffusion;
 Emulsions and suspensions;
 Steady shear flows viscometric flow;
 Suspensions dispersions pastes slurries colloids;
 Particleladen flows