Investigation of the dispersing characteristics of antral contraction wave flow in a simplified model of the distal stomach

Abstract

The dispersing characteristics of antral contraction wave (ACW) flow in the antrum are investigated by reproducing the flow generated by an ACW and determining its effect on liquid drops. The goal is to gain information about the flow field and mechanical stresses, which are responsible for the food disintegration. Toward this end, a model antrum prototype was constructed, consisting of a cylinder that was closed at one end to represent the antrum and closed pylorus. A moving hollow piston with a parabolic inner contour was used to model an ACW. A computational model was developed that reflects this prototype. Experiments and simulations were first performed for fluids with different rheological properties, two relative occlusions (0.60 and 0.75), and several ACW speeds (1.0–7.5 mm/s). The simulations were validated with velocity measurements, and the characteristics of the retropulsive jet were quantified at different Reynolds numbers (0.5–105.3). Experiments were then performed in which liquid drops of different viscosity were placed in a highly viscous fluid with low interfacial tension, similar to conditions in a stomach. It was found that the viscosity ratio (0.001–0.1) influences the retraction dynamics of a drop's tail after stresses are relaxed. The flow and stress information from the simulations was used to analyze fluid transport in the antrum and to quantify drop breakup conditions. It was found that a drop broke up if both a critical capillary number of 0.51 was exceeded and the drop passed within a critical dimensionless distance of 0.3 to the wave apex.

Multivariate Peristalsis in a Straight Rectangular Duct for Carreau Fluids

“…The wavelike motion of a model stomach is studied by Alokaily et al [20], focusing on the mixing flow at the beginning of the digestion. The dispersing characteristics of antral contraction are in vitro investigated using an antrum prototype by Dufour et al [21], and the drop behavior and breakup under peristalsis are simulated computationally by Feigl and Tanner [22].…”