Study on Fluid Dynamic Characteristics of Turbulent Blood Flow

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The pressure - flow rate relationship in the ventricular assist system consisting of an artificial heart is helpful in order to diagnose and detect abnormal condition of the system, or to develop indirect measurement system which saves sensors for pressure and flow rate of the device being used. For example, we have developed the indirect flow rate measurement system using the power consumption of the driving motor of the centrifugal blood pump. This relationship, however, is subject to the physical properties of blood as well as the configuration of the system. The physical properties of flowing blood, or rheology of blood, is essential for such aims, but reports on physical properties of flowing blood under turbulent state, which is often observed in the mechanical assisting devices like artificial hearts, has hardly been investigated. The pressure drop across the circular pipe of turbulent flow was measured and compared between goat blood and a Newtonian fluid. Goat blood demonstrat … More ed slight decrease in the pressure drop than the Newtonian fluid, and the magnitude of the decrease in pressure drop was independent of blood cell concentration. The indirect measurement of flow rate of a centrifugal blood pump using motor power consumption was attempted, in which the effect of viscosity change on the accuracy was investigated. The centrifugal blood pump developed in our research institute was installed between the left apex and the descending aorta making a left heart bypass. The flow rate measured by this method has demonstrated sufficient accuracy for practical use when the viscosity is known. The extent of errors fluctuated with the change of hematocrit after in the course of time after surgical operation. The errors could be corrected by measuring the viscosity of the blood to the practically acceptable range by calibration data obtained with Newtonian fluids. The difference in pressure drop in turbulence due to Non-Newtonian properties, which was observed in the turbulent pipe flow, was found to have negligible effects in this measurement method of flow rate for the practical use. Less