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

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