Direct simulation of drying colloidal suspension on substrate using immersed free surface model

This paper presents a new direct simulation method for a drying colloidal suspension on a substrate. A key issue of the present method is the immersed free surface model proposed by the authors, which enables us to estimate accurately and efficiently capillary forces exerted on particles on a free surface. Using the immersed free surface model along with immersed boundary method and level set method, the present method leads to a three-way coupling of the fluid flow, the free surface motion and the particle motion. In addition, the present method includes a way of curvature estimation using virtual grid differencing to calculate accurately a surface tension. The way of curvature estimation is quantitatively validated through the simulation of a still droplet. The immersed free surface model is quantitatively validated through the simulation of a sphere moving across a free surface and the simulation of two spheres moving along a free surface. Finally, simulations of drying colloidal suspension containing 130 particles are performed to demonstrate the applicability of the present method to actual systems. •We model mesoscale gas–liquid–solid three-phase flow.•We estimate efficiently capillary force exerted on mobile particles at free surface.•We estimate accurately curvature of free surface.•We simulate structure formation of colloidal suspension on substrate during drying.•We clarify effect of wettability of particles on structure formation.