Dissolution characteristics of solutes with different shapes using the moving particle semi-implicit method

Abstract

Dissolution characteristics of solutes with different shapes are studied. To simulate the process of dissolution, a diffusion and dissolution model based on the moving particle semi-implicit (MPS) method is proposed. First, the diffusion equation is introduced to the MPS method. Compared with the analytical solution, concentration diffusion can be accurately simulated with the model. Then, a coupling relationship between concentration, density, and viscosity is established. The relationship deals with the changes in physical parameters of the fluids caused by the diffusion, affecting the fluid flow. As the density change cannot be ignored in the mass conservation equation, the equation is re-deduced in this paper. In addition, the dissolution model is introduced to the MPS method. The dissolution model is verified by the dissolution simulation of sessile droplets in water. Finally, the dissolution of solutes with different shapes in water is simulated using the proposed method. Five cases with different solute shapes are set to simulate five different drugs. Five cases with different solute shapes are set to simulate five different drugs. The solid solute shapes used are rectangle, capsule, heart-shaped, and circle, and the liquid solute is a rectangle shape. The dissolution of the solute is comprehensively affected by the contact between the solute and water, the concentration difference, and the intensity of convection. The small concentration difference and the low convective velocity cause the existence of insoluble points in the heart-shaped case, which decreases the dissolution rate. Dimensional analysis is carried out to address the relative importance of diffusion to convection. In the dissolution of solutes with different shapes, the effect of convective cannot be ignored when the non-dimensional number is lower than 2.5 × 10−5.