The Dispersing Characteristics of Antral Contraction Wave Flow in a Model Stomach

Experiments and numerical simulations are used to study the flow field and particle breakup due to mechanical stresses in a model human stomach. A simplified artificial stomach was constructed, consisting of a tube which was closed at one end to represent the antrum and the closed pylorus. Antral contraction waves were modeled by a moving hollow piston. The computational domain used in the simulations mirrored this setup. Experiments and simulations were performed for different fluid systems, relative occlusions and wave speeds. Velocity profiles, measured along the centerline using ultrasound Doppler, were used to validate the numerical simulations. The retropulsive jet and velocity were similar to those from simulations in complex 3D geometries of the stomach and with in-vivo measurements. Liquid drops of different sizes and initial locations were then tracked through the flows and their breakup behavior was recorded. The fluids were highly viscous and the interfacial tension was low to represent the conditions in the stomach. The strain rates and stresses along the various particle paths were determined from the simulations. Combining this particle tracking information with drop breakup behavior from the experiments, different breakup conditions and regimes were identified.