Nonlinear analysis of aortic flow in living dogs.

A nonlinear theory which considered the convective accelerations of blood and the nonlinear elastic behavior and taper angle of the vascular wall was used to study the nature of blood flow in the descending thoracic aorta of living dogs under a wide range of pressures and flows. Velocity profiles, wall friction, and discharge waves were predicted from locally measured input data about the pressure-gradient wave and arterial distention. Precision pressure-gradient waves free of static errors were obtained through forward and backward pressure-gradient measurements, and the arterial pressure—radius relation was obtained through cinematography using a telephoto lens. The results indicated that a major part of the mean pressure gradient was balanced by convective accelerations; the theory, which took this factor into account, predicted the correct velocity distributions and flow waves. The results also showed that for high flow rates the magnitude of the peak wall-shear stress became comparable to the yield stress of the endothelial surface and that radial flows of significant magnitude existed with respect to the arterial wall.