Simulating the hydrodynamics of self-propelled colloidal clusters using Stokesian dynamics.

Self-propelled clusters are involved in many technological applications such as in material science and biotechnology, and understanding their interaction with the fluid that surrounds them is of a great importance. We present results of swimming velocity and energy dissipation obtained through Stokesian dynamics simulations of self-propelled clusters. The clusters are of diffusion limited aggregates, consisting of force- and torque-free spherical particles. The number of particles per cluster ranges from 100 to 400, and with two fractal dimensions of 2.1 and 2.4. The clusters are self-propelled by imposing an explicit gait velocity applied in the x, y, and z directions. It is found that the swimming velocity of the cluster and the energy dissipation are strongly dependent on the number of particles in the cluster and its fractal dimension and on the orientation of the imposed explicit gait velocity. It was found that the rotational velocity of the self-propelled clusters decreases as the number of particles within the cluster is increased, in line with experimental observations reported recently in the literature.