Flow and mixing induced by single, colinear, and colliding contractile waves in the intestine

Abstract

The flow of liquid food bolus in different intestinal contraction regimes is studied experimentally, analytically, and numerically. We show that a particle subjected to a peristaltic wave has a nonintuitive propulsion-reflux motion. When multiple waves are generated sequentially, as happens in the gut, reflux is found to be maximized for an inter-wave length corresponding to that observed physiologically in animals, indicating a possible evolutionary bolus absorption optimization. We find that counter-propagating waves generate a high-pressure region from which high-velocity bolus jets emerge. As a result, these waves generate 80 times more mixing than waves going in the same direction.