Meeting Abstract
Although valveless tubular hearts are common throughout metazoans, the mechanism by which these hearts drive fluid flow is under dispute. Traditionally, peristalsis was used to describe the pumping mechanism of many non-chambered hearts, but recently other mechanisms have been used (e.g. dynamic suction pumping) due to observations of fluid flow patterns that presumably rule out peristalsis. However, the technical definition of peristalsis, and the fluid flow patterns that it predicts, is based on a small-amplitude, long-wave approximation which is often violated by pumps found in nature. Here we suggest a definition of peristalsis that can be used to evaluate pumps that is more inclusive and relevant to biological structures: the presence of non-stationary compression sites that propagate unidirectionally along a tube without the need for a structurally fixed flow direction. We present direct numerical simulations of a pump operating under this biologically relevant definition to explore how flows can differ from a technical definition: flow speeds can be greater than the speed of the compression wave; fluid flow can be pulsatile; and flow speed can have a nonlinear relationship with compression frequency when compression-wave speed is held constant. These results demonstrate that our simpler, more inclusive definition is better equipped to assess the pumping mechanism in a biological pump than the technical definition of peristalsis.
