A steady flow analysis on the stented and non-stented sidewall aneurysm models

As part of a general investigation on the effects of blood flow patterns in sidewall aneurysm, in vitro steady flow studies on rigid aneurysm models h ave been conducted using Particle Image Velocimetry over a range of Reynold s number from 200 to 1600. Above Reynolds number 700, one large recirculati ng vortex would be formed, occupying the entire aneurysmal pouch. The centr e of the vortex is located at region near to the distal neck. A pair of cou nter rotating vortices would however be formed at Reynolds numbers below 70 0. For all the aneurysm models considered, the vortex strength, in general, is stronger at higher Reynolds numbers but lower at larger aneurysm size. Maximum strength of the vortex is about 15% of the bulk mean velocity in th e upstream parent tube. Estimates of the wall shear stresses are derived fr om the near wall velocity measurements. Highest level of wall shear stresse s always appears at the distal neck of the aneurysmal pouch. Stents and spr ings of different porosity have been used to dampen the flow movement insid e the aneurysm so as to induce the possible formation of thrombosis. It is found that the flow movement inside the aneurysmal pouch can be suppressed to less than 5% of the bulk mean velocity by both devices. Furthermore, reg ions of high wall shear stresses at the distal neck could also be suppresse d by almost 90%. The present results would be useful for further improvemen ts in stent (or spring) technology. (C) 1999 IPEM. Published by Elsevier Sc ience Ltd. All rights reserved.