Computational Fluid Dynamics

Researchers: Eunok Jung, ORNL; Charles Peskin, NYU/Courant

Computational scientists at ORNL have recently verified that fluid can be pumped without the presence of valves in the system. Specifically, the computational model, using the immersed boundary method, produces net flow in an oval tube with periodic forcing applied to a flexible membrane that forms part of the tube. A startling result is that the direction and magnitude of the flow depends upon the frequency of the forcing function. The research will now be applied to model cardiopulmonary resuscitation. During CPR, it is not yet known whether the heart acts as a pump (through cardiac pumping), or as a passive conduit for valveless pumping (thoracic pumping). There is some echocardiographic evidence to suggest that the mitral valve remains open during CPR in the thoracic pump model. The immersed boundary method will be applied to a heart model to help understand the mechanism of blood flow during CPR and to provide insight into the development of more effective CPR techniques.

160 particles at t=100

160 particles at t=200

Pumping blood in one direction is the main function of the heart, and the heart is equipped with valves that ensure unidirectional flow. Is it possible, though, to pump blood without valves? This project is intended to show by numerical simulation using the Immersed Boundary Method the possibility of a net flow that is generated by a valveless mechanism in a circulatory system.

The direction and magnitude of flow inside a loop of tubing which consists of (almost) rigid and flexible parts are investigated when the boundary of one end of the flexible segment is forced periodically in time. Despite the absence of valves, a net flow around the loop is produced in these simulations and, surprisingly, the direction and magnitude of this flow depend on the frequency and amplitude of the periodic driving force.

One of the applications of valveless pumping is cardiopulmonary resuscitation (CPR). The blood flow during CPR has been explained by two conventional theories: thoracic pump and cardiac compression mechanisms. In the thoracic pump model, it has been reported that the heart is viewed as "a passive conduit for blood flow" during chest compression with an open mitral valve throughout the cardiac cycle and anterograde (forward) transmitral blood flow even during chest compression. However, in the cardiac pump model, the heart acts as a pump and its valves function normally during the entire cycle of CPR. Our computational model of valveless pumping might be applicable to the thoracic pump model. An optimized our model helps finding effective methods for maximizing blood flow during CPR and understanding the thoracic pump mechanism. more images

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Updated: Friday, 27-Oct-2000 17:11:12 EDT