Characterization of peristaltic flow during the mixing process in a model human stomach
Characterization of peristaltic flow during the mixing process in a model human stomach
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DOI：
10.1063/1.5122665
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发表时间：
2019-10-01
影响因子：
4.6
通讯作者：
Tanner, Franz X.
中科院分区：
文献类型：
--
作者：
Alokaily, Samer;Feigl, Kathleen;Tanner, Franz X.
通过数值模拟来研究混合和消化过程中模型胃中蠕动流的特征。胃的几何模型由一根不同直径的轴对称管组成，一端有壁，代表胃窦和闭合的幽门。产生蠕动流的胃窦收缩波 (ACW) 被建模为使边界变形并从而使计算网格变形的行波。该几何模型被实施到开源代码 Open FOAM 中。进行参数研究，其中改变流体粘度、波速、波宽度和最大相对闭塞。研究了这些参数对幽门附近引起的后推射流以及连续 ACW 对之间的再循环的影响。这两种流动特征都有助于混合和消化过程。反推射流通过其峰值速度和沿中心线的长度来量化。对于每种波几何形状，对于低雷诺数，这些量与雷诺数无关，而对于超过 1 的雷诺数，随着雷诺数的增加，峰值中心线速度减小，射流长度增加。此外，发现速度和压力曲线在低雷诺数下与波速成比例。在不同的波浪几何形状之间，提出并测试了峰值中心线速度和射流长度的比例定律。粒子跟踪和涡度图表明，当相对遮挡增加以及粘度或波宽减小时，混合效率会增加。由 AIP Publishing 许可发布。
Numerical simulations are performed to investigate the characteristics of peristaltic flow in a model stomach during the mixing and digestion process. The geometrical model for the stomach consists of an axisymmetric tube of varying diameter with a wall at one end, representing the antrum and closed pylorus. The antral contraction waves (ACWs) that produce the peristaltic flow are modeled as traveling waves that deform the boundary and consequently the computational mesh. This geometrical model is implemented into the open source code Open FOAM. A parametric study is performed in which the fluid viscosity, wave speed, wave width, and maximum relative occlusion are varied. The effect of these parameters on the retropulsive jet induced near the pylorus and the recirculation between pairs of consecutive ACWs is investigated. Both of these flow features contribute to the mixing and digestion process. The retropulsive jet is quantified by its peak velocity and length along the centerline. For each wave geometry, these quantities are found to be independent of the Reynolds number for low Reynolds numbers, while for Reynolds numbers exceeding one, the peak centerline velocity decreases and the jet length increases as the Reynolds number increases. Moreover, the velocity and pressure curves are found to scale with the wave speed at low Reynolds numbers. Between different wave geometries, scaling laws are proposed and tested for the peak centerline velocity and jet length. Particle tracking and vorticity plots show that mixing efficiency increases when the relative occlusion increases, as well as when the viscosity or wave width decreases. Published under license by AIP Publishing.