Modeling moisture infusion in ceramic using Richards equation: Experimental and analytical validations, and exploration of three time-dependent wetting scenarios

Abstract

Spontaneous imbibition of water into ceramic tile is modeled using the well-known Richards equation (RE) employed for modeling unsaturated flow in the vadose zone. The Brooks and Corey model for relative permeability and Van Genuchten model for capillary pressure is employed to generate the final form of RE that predicts moisture migration in porous ceramic. COMSOL is employed to numerically solve RE in a cuboid, block like ceramic geometry. The simulation results, obtained using the mesh optimized through a grid independence test, are validated in three different ways. First, the simulation predictions are compared with the experimental results obtained from a neutron microscope imaging study of wetting of a ceramic block. Good qualitative and quantitative matches were obtained. Later, the simulation predictions for a 1-D moisture migration situation were compared with two different published analytical solutions, and once again, good agreements were observed. After the code validation, simulations for moisture migration through evolving saturation plots were carried for three different cases of the ceramic-block top getting wetted by falling drops: a single droplet, two droplets with a time gap, and continuous droplets. Evolution of saturation plots were studied where the third case was observed to cause the maximum water infiltration into ceramic.