A computational model for pumping in the tubular embryonic heart including fluid-solid interaction

In this work we have studied the pumping problem of the embryonic chick heart at stage 12 and stage 16 (2 and 2.5 days of a 21-day incubation period). During this time period, the heart is a curved tube consisting of myocardium, cardiac jelly, and a thin layer of endocardium. Blood enters one end of the tube and exits the other. While the blood is driven by the movement of the heart wall, pressure builds up inside the heart and deforms the heart in return. The purpose of this work is to study the coupling between the heart wall movement and the blood flow inside the heart.; As an approximation, the curved tubular heart is modeled as a straight tube, and both the fluid and the solid problems are assumed to be axisymmetric. Blood is modeled as a Newtonian fluid and the flow is viscosity dominated. Traditional lubrication theory is applied to solve the fluid problem, and a computer program is developed to obtain the numerical solution.; The heart is first modeled as an elastic membrane tube for the stage 12 heart. Then a finite element procedure is introduced to model the heart as a thick-walled tube with different material properties for the myocardium and cardiac jelly. The FEM procedure combined with the fluid program is used to study the peristaltic pumping of the stage-12 uniform tubular heart and the pumping of the stage-16 heart with endocardial cushions. Local variables, such as pressure and shear stress, and global functions, such as pumping performance and pressure-volume loops are given as results. The effects of cardiac jelly and endocardial cushions are discussed. In particular, the transition from peristaltic to pulsatile flow was investigated by applying different contracting wave shapes. The effects of wave length, amplitude, speed and intervals between the waves are also studied.; Results show that cardiac jelly helps pump against a higher pressure rise and makes the heart a more efficient pumping system. Endocardial cushions are important in the blood flow transformation from peristaltic to pulsatile. Higher wave amplitude and speed create higher pressure, wall shear stress, and higher pumping performance.