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Review
. 2010 Sep;75(7):R151-62.
doi: 10.1111/j.1750-3841.2010.01748.x.

Modeling the fluid dynamics in a human stomach to gain insight of food digestion

M J Ferrua  1 , R P Singh
Affiliations
Free PMC article
Review

Modeling the fluid dynamics in a human stomach to gain insight of food digestion

M J Ferrua et al. J Food Sci. 2010 Sep.
Free PMC article

Abstract

During gastric digestion, food is disintegrated by a complex interaction of chemical and mechanical effects. Although the mechanisms of chemical digestion are usually characterized by using in vitro analysis, the difficulty in reproducing the stomach geometry and motility has prevented a good understanding of the local fluid dynamics of gastric contents. The goal of this study was to use computational fluid dynamics (CFD) to develop a 3-D model of the shape and motility pattern of the stomach wall during digestion, and use it to characterize the fluid dynamics of gastric contents of different viscosities. A geometrical model of an averaged-sized human stomach was created, and its motility was characterized by a series of antral-contraction waves of up to 80% relative occlusion. The flow field within the model (predicted using the software Fluent™) strongly depended on the viscosity of gastric contents. By increasing the viscosity, the formation of the 2 flow patterns commonly regarded as the main mechanisms driving digestion (i.e., the retropulsive jet-like motion and eddy structures) was significantly diminished, while a significant increase of the pressure field was predicted. These results were in good agreement with experimental data previously reported in the literature, and suggest that, contrary to the traditional idea of a rapid and complete homogenization of the meal, gastric contents associated with high viscous meals are poorly mixed. This study illustrates the capability of CFD to provide a unique insight into the fluid dynamics of the gastric contents, and points out its potential to develop a fundamental understanding and modeling of the mechanisms involved in the digestion process.

Practical application: This study illustrates the capability of computational fluid dynamic techniques to provide a unique insight into the dynamics of the gastric contents, pointing out its potential to develop a fundamental understanding and modeling of the human digestion process.

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Figures

Figure 1
Figure 1
A schematic diagram of a human stomach.
Figure 3
Figure 3
Construction of a 3-D model of the average human stomach. (A) Series of circles used to develop the 3D geometry of the stomach model. (B) Isometric view of the final geometrical model.
Figure 2
Figure 2
Two-dimensional image used to develop the geometrical model of an average-sized human stomach.
Figure 4
Figure 4
Motility pattern of the ACWs during digestion. (A) Origin and average-velocity of ACWs. (B) Width of the ACWs. (C) Direction and amplitude of the ACWs.
Figure 5
Figure 5
Image of the motility pattern of the gastric wall as numerically simulated.
Figure 6
Figure 6
Boundary conditions. (A) Boundary types. (B) Deformation of stomach walls.
Figure 8
Figure 8
Effect of viscosity on the formation of the retropulsive-jet like motion and eddy structures. Streamlines of the fluid flow within the stomach's middle plane at t+ 10 s, colored by velocity magnitude (cm/s).
Figure 7
Figure 7
Gastric flow at t+ 10 s for a Newtonian fluid (0.001 Pa.s). (A) Streamlines of the fluid flow, colored by velocity magnitude (cm/s). (B) Contour of the velocity field in the middle plane of the stomach model.
Figure 9
Figure 9
Quantitative characterization of the retropulsive jet and eddy structures that developed within the antropyloric region, as the ACWs propagate toward the pylorus (Newtonian fluid, 0.001 Pa.s).
Figure 11
Figure 11
Effect of the rheological properties of gastric contents on the average value of the vorticity field predicted within the antropyloric region.
Figure 10
Figure 10
Effect of viscosity on the vorticity of the flow field. Contour of vorticity within the stomach middle plane at t+ 10 s (lower part of the stomach).
Figure 12
Figure 12
(A) Experimental system used to measure the flow field that develops within an acrylic chamber due to the peristaltic deformation of one of its walls. (B) Instantaneous streamlines of the velocity fields experimentally measured using PIV (cm/s).
Figure 13
Figure 13
Effect of viscosity on the pressure fields that develop within the stomach's middle plane at t+ 10 s.
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