Simulation of droplet spreading on porous substrates using smoothed particle hydrodynamics

Small-scale fluid phenomena are being studied in many areas of engineering and research. This article focuses on small-scale droplet spreading and absorption on a porous substrate based on the SPH (Smoothed Particle Hydrodynamics) method. Three main factors that affect this process were considered: contact angle, pore sizes and gravity. Three various intrinsic contact angles, two different pore sizes with same porosity in comparison with flat surface and four different gravity conditions (g = 0 m/s2 included) were applied to simulate the droplet spreading on porous substrates. The results show that the dependence of wetting region radius on time for both flat and porous substrates can be well divided into two spreading stages, i.e. a power-law inertial stage and viscous stage. To illustrate the counterbalance between droplet spreading and absorption, the evolution of liquid drop height was also examined, which indicates that the drop height decreases, while the wetting region radius increases as intrinsic contact angle decreases for both pore sizes. Besides that the effect of gravity on droplet spreading dynamics is also presented.