Dynamics of a spherical colloid at a liquid interface: A lattice Boltzmann study

We study the dynamics of a spherical colloidal particle pulled along the fluid-fluid interface using lattice Boltzmann (LB) simulations. We consider an interface with a finite width and include both the effects of the thermodynamics of the interface and the particle wetting, characterized by the contact angle θ between the particle surface and the interface, in addition to the viscosity ratio λ between the two fluids. We characterize the particle dynamics by applying a constant pulling force along the interface and measure both the translational and the rotational dynamics as a function of the contact angle and the viscosity ratio. We observe that the hydrodynamic drag is reduced and the particle rotation is increased when the particle resides more in the low viscosity fluid, in agreement with previous hydrodynamic theories. We also study the case where the particle rotation is suppressed, and find an overall increase of the drag coefficient.