Fluid-Structure-Acoustic Interaction Study on Abdominal Aortic Aneurysms: Application in Phonoangiography

Computational Fluid-Structure-Acoustic Interaction (FSAI) study is presented for effect of Abdominal Aortic Aneurysm (AAA) width and height on hemodynamic parameters and cut-off frequency of sound spectrum on skin surface. An in-house FSAI solver, developed using Arbitrary Lagrangian-Eulerian (ALE) framework with Finite-Volume (Flow and Structure) and Finite-Difference (Acoustics) discretisation, is employed to perform axisymmetric blood flow simulations in artery with fusiform aneurysm. The velocity fluctuation, which is usually sensed by a digital stethoscope is calculated on the skin surface corresponding to pulsatile inlet flow at Womersley number (Wo) of 16.5. Vortex shedding from distal end of aneurysm during decelerating systolic stage and their further impingement and dissipation on aneurysm wall leads to pressure fluctuation and thereby characteristic frequencies. The motion of recirculation zones, along narrow aneurysm wall leads to higher Wall Shear Stress; whereas impingement of shorter length and higher energy scale vortices, for aneurysm with larger height, leads to higher frequencies. The current work provides a physical perspective behind Hemoacoustics and Hemodynamics of AAA which can lead to development of non-invasive diagnostic technique ‘phonoangiography’.