A multiscale lattice Boltzmann model of macro- to micro-scale transport, with applications to gut function

作者：Wang Yanxing; Brasseur James G^*; Banco Gino G; Webb Andrew G; Ailiani Amit C; Neuberger Thomas

来源：Philosophical Transactions of the Royal Society A-Mathematical Physical and Engineering Sciences, 2010, 368(1921): 2863-2880.

DOI：10.1098/rsta.2010.0090

• gastrointestinal
• intestine
• gut
• absorption
• villi
• lattice Boltzmann method

Nutrient absorption in the small intestine cannot occur until molecules are presented to the epithelial cells that line intestinal villi, finger-like protrusions under enteric control. Using a two-dimensional multiscale lattice Boltzmann model of a lid-driven cavity flow with 'villi' at the lower surface, we analyse the hypothesis that muscle-induced oscillatory motions of the villi generate a controlled 'micro-mixing layer' (MML) that couples with the macro-scale flow to enhance absorption. Nutrient molecules are modelled as passive scalar concentrations at high Schmidt number. Molecular concentration supplied at the cavity lid is advected to the lower surface by a lid-driven macro-scale eddy. We find that micro-scale eddying motions enhance the macro-scale advective flux by creating an MML that couples with the macro-scale flow to increase absorption rate. We show that the MML is modulated by its interactions with the outer flow through a diffusion-dominated layer that separates advection-dominated macro-scale and micro-scale mixed layers. The structure and strength of the MML is sensitive to villus length and oscillation frequency. Our model suggests that the classical explanation for the existence of villi-increased absorptive surface area-is probably incorrect. The model provides support for the potential importance of villus motility in the absorptive function of the small intestine.

• 出版日期2010-6-28