The shear rate at the wall in a symmetrically branched tube simulating the aortic bifurcation.

The purpose of this study was to determine the shear rate at the wall in a symmetrically branched tube with a branch-to-trunk area ratio and angle of branching that were comparable to the human abdominal aorta. Velocity profiles were measured with a laser Doppler anemometer during steady and pulsatile flow in which the mean Reynolds numbers were 500, 1000, and 1500. During both steady and pulsatile flow, as the Reynolds numbers increased, the shear rates at the inner wall of the branch increased. Only slight increments of the shear rates occurred along the outer wall of the branch, however, as the Reynolds number increased. No reversals of flow were observed at any Reynolds number during steady flow. Transient reversals of flow (causing negative shear rates) occurred along the outer wall of the branch at a Reynolds number of 500; but such transient flow reversals were not observed at the higher Reynolds numbers during pulsatile flow.