GİRİŞ HIZ PROFİLİ VE GİRİŞ UZUNLUĞUNUN ABDOMİNAL AORT ANEVRİZMASI HEMODİNAMİĞİ SİMÜLASYONLARINA ETKİSİ

Abstract

In computational Abdominal Aortic Aneurysm (AAA) hemodynamics studies, along with adjusting the problem geometry, mesh, transport, turbulence and rheology models; setting up boundary conditions (BC) is also a very important step which affect the reliability and accuracy of the hemodynamic assessment. The transient effects of physiological flow are well described by the Womersley profile, though its application might be difficult due to the complex nature of functions involved. Conversely, in literature, studies utilizing Plug or Parabolic profiles as inlet boundary conditions generally requires large entrance lengths to obtain the exact characteristics of the Womersley profile. In the current study, the differences arising between those boundary conditions, Womersley, Parabolic and Plug, with different entrance lengths, L_(ent )=D,3D and 11D, are examined by comparing the results with a Base condition, which is a solution obtained with ensured fully-developed flow before entering the aneurysm sac at two physiological flow conditions with mean Reynolds numbers, 〖Re〗_m=340 and 1160. The results reveal that with increasing mean flow rate, applying the complex Womersley equation might not be necessary. For the inlet flow waveform with 〖Re〗_m=1160, the Parabolic profile can be used instead of the Womersley profile by supplying an entrance length L_(ent )= 3D. On the other hand, the Plug profile requires an entrance length at least L_(ent )= 11D to replicate the Base condition for waveform with 〖Re〗_m=340.