Numerical study on the effect of secondary flow in the human aorta on local shear stresses in abdominal aortic branches

Flow in the aortic arch is characterized primarily by the presence of a str ong secondary flow superimposed over the axial flow, skewed axial velocity profiles and diastolic flow reversals. A significant amount of helical flow has also been observed in the descending aorta of humans and in models. In this study a computational model of the abdominal aorta complete with two sets of outflow arteries was adapted for three-dimensional steady flow simu lations. The flow through the model was predicted using the Navier-Stokes e quations to study the effect that a rotational component of flow has on the general flow dynamics in this vascular segment. The helical velocity profi le introduced at the inlet was developed from magnetic resonance velocity m appings taken from a plane transaxial to the aortic arch. Results showed th at flow division ratios increased in the first set of branches and decrease d in the second set with the addition of rotational flow. Shear stress vari ed in magnitude with the addition of rotational flow, but the shear stress distribution did not change. No regions of flow separation were observed in the iliac arteries for either case. Helical flow may have a stabilizing ef fect on the flow patterns in branches in general, as evidenced by the decre ased difference in shear stress between the inner and outer walls in the il iac arteries. (C) 2000 Elsevier Science Ltd. All rights reserved.