<i>In silico</i> study of the dynamics of solid food particles in the stomach during gastric digestion

In recent years, there has been growing interest in computational fluid dynamics models of the gastric phase of the digestion process. While several models address the digestion and emptying of liquid meals, none incorporate large solid food particles. This omission is significant, as a food bolus typically contains solid particles of varying sizes, with those exceeding 1-2 mm unable to pass through the pylorus. The current study integrates large spherical particles into an imaging-based stomach model to examine the action of hydrodynamic and contact forces on these particles. The model captures particle shuttling dynamics and quantifies the forces that drive trituration in a healthy and a hypomotile stomach at different viscosities of the surrounding liquid contents. The results show that the presence of solid foods can reduce the gastric emptying rate of liquids while also significantly influencing the flow inside the antrum. Hypomotile stomachs were ineffective in trapping the solids next to the pylorus, with many food particles never even making it to the terminal antrum, unlike the healthy case. The pressure, shear stresses and contact forces acting on the solid particles were also lower for the hypomotile case.