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

The three-dimensional flow through a rigid model of the human abdominal aor ta complete with iliac and renal arteries was predicted numerically using t he steady-state Navier-Stokes equations for an incompressible, Newtonian fl uid. The model adapted for our purposes was determined from data obtained f rom cine-CT images taken of a glass chamber that was constructed based on a natomical averages. The iliac arteries had a bifurcation angle of approxima tely 35 degrees and a branch-to-trunk area ratio of 1.27, whereas the renal arteries had left and right branch angles of 40 degrees and an area ratio of 0.73. The numerical tool FLOW3D (AEA Industrial Technology, Oxfordshire, UK) utilized body-fitted coordinates and a finite volume discretization pr ocedure. Purely axial velocity profiles were introduced at the entrance of the model for a range of cardiac outputs. The four-branch numerical model d eveloped for this investigation produced flow and shear conditions comparab le to those found in other reported works. The total wall shear stress dist ribution in the iliac and renal arteries followed standard trends, with max imum shear stresses occurring in the apex region and lower shear stresses o ccurring along the lateral walls. Shear stresses and flow rate ratios in th e downstream arteries were more effected by inlet Re than the upstream arte ries. These results will be used to compare further simulations which take into effect the rotational component of flow which is present in the aortic arch. (C) 1998 Elsevier Science Ltd. All rights reserved.