Shape Effects on the Drag Force and Motion of Nano and Micro Particles in Low Reynolds Number Flows

Particulate flows are commonly found in a variety of applications. For example, nanoparticles have been used in targeted drug delivery systems and improving heat transfer in nanofluids. Crucial to the development of technologies that incorporate nanoparticles is to understand the effect of a nanoparticle’s shape on its motion. The effect of shape on nanoparticles used in drug delivery, in particular, is a very active area of experimental investigation. Also, the determination of the coefficients of hydrodynamic forces or drag forces on nanoparticles of different shapes is crucial in designing effective nanoparticle-mediated therapies. In this study we present a resolved discrete particle method (RDPM), which is also called the Direct Numerical Simulation (DNS), to investigate the effect of shape on drag force in a vicious fluid. Three different shapes of particles are studied: a sphere, a probate ellipsoid, and an oblate ellipsoid. These particles have the same volume and are placed in contact with the bottom wall in simple shear flows. Their drag forces are computed numerically; it is found that the particle shape has a significant effect on the drag forces. In the case of a spherical particle, our results agree very well with the analytical results found in the literature. The motion of three particles of the same volume but different shape in a simple shear flows are also simulated. It shows that different particle shapes cause particles to experience different hydrodynamics forces, leading them to different velocities and paths.