Simulation and analysis of mass transfer and absorption process intensification by villi movement

The inner wall of the digestive organ has a multi-level and multi-scale structure and complex movement patterns. Understanding its role in the process of digestion and absorption is of great significance to human health. From a chemical engineer's unique perspective, this work developed a multi-physics computational fluid dynamics (CFD) model to describe nutrient transfer and absorption in the small intestine driven by villi movement. The moving mesh method was successfully implemented to realize the cyclic back-and-forth movement of villi. Furthermore, data analysis methods were developed to quantify mass transfer and absorption performance. Numerical simulation results show that the back and forth movement of villi along the axial direction can generate two characteristic vortexes. The formation of vortexes can effectively reduce mass transfer resistance in the radial direction. The top part of villi plays critical role in nutrient absorption. A shorter movement cycle offers a higher villi velocity, which results in a higher value of the maximum enhancement factor and hence a higher absorption amount. The case with taller villi demonstrates higher mass-transfer enhancement factor. At the same time, taller villi offer larger absorption area. These two positive factors together contribute to a much higher absorption amount as compared with the case with shorter villi. In this specific study, the case with 900 μm high villi and a movement cycle of 6 s, the mass transfer performance can be improved by over 500% as compared to the case without villi movement (i. e., a mass-transfer enhancement factor reaching 6). © All Right Reserved.