(533j) Brownian Dynamics Simulations of Cubic Nanoparticle Suspensions

Mallavajula, R. - Presenter, Cornell University
Archer, L. A., Cornell University
Koch, D. L., Cornell University

The rheological properties of suspensions of Brownian cube-shaped particles are interesting because of the greater increase in the translational freedom caused by layering relative to suspensions of Brownian spheres. 

At very low volume fractions, the sharp edges and corners affect flow profile around the cube. In the finite element method, the sharpness of the edges and corners can be varied using the grid spacing on the surface of the cube. The stress acting on the particle was found to increase with the sharpness of the cube. A theoretical scaling for this increase was predicted using the 2D flow profile around the corners. The results for the stress were fitted with this scaling to obtain the results for the cubes with sharp edges and corners. At moderate volume fractions, Brownian dynamics simulations were carried out to study the structure and flow behavior of suspensions. Simulations were performed over wide range of volume fractions and Pectlet numbers.  Under shear, cubic particles were observed to behave like spheres circumscribed over it for volume fractions less than 0.25. Interesting differences in the rheological properties between spheres and cubes are analyzed based on the structure, order parameters, rotational and translational diffusivities of the particles in the suspension.