Meeting Abstract

24.3  Monday, Jan. 5  Modeling blood flow through amphibian hearts using flow visualization and the immersed boundary method HAMLET, C.L.*; MILLER, L.A.; The University of North Carolina at Chapel Hill chamlet@email.unc.edu

Amphibian hearts are characterized by three chambers: two thin-walled atria and a single ventricle with a thick, spongy lumen. The left atrium pumps oxygenated blood into the ventricle and out into body. The deoxygenated blood returns through the venous circulation to the right atrium, into the ventricle, out through the pulmonary artery, and into the lungs. Amphibians may also initiate cutaneous respiration and obtain oxygen primarily through the skin. There are many proposed mechanisms for the flow of oxygenated and deoxygenated blood through a single ventricle, but no clear understanding of how mixing is prevented. Laminar blood flow is commonly proposed as a mechanism since intracardiac pressures are low, allowing the two flows to move against one another with minimal mixing. It has also been suggested that sequential contraction of different parts of the heart keeps the oxygenated and deoxygenated blood separated. The right atrium contracts slightly earlier than the left atrium, and deoxygenated blood moves through the ventricle earlier than the oxygenated blood. The spiral valve alternately blocks flow into the systemic arch or pulmonary arch. The thickened lumen is also believed to play a role in directing fluid flow, though the exact mechanism is unclear. Assuming laminar flow is the primary cause of maintaining separation of the two blood flow suggests constraints on the Reynolds number of the flow or on the size to which an amphibian heart can grow, which in turn constrains the body size of amphibians. In this study, we will construct a simplified physical model to test the laminar flow hypothesis using flow visualization techniques. The role of the thickened lumen will be explored using the physical model. Computational fluid dynamics using the immersed boundary method will be used to consider asynchronous contractions in the heart.