Computational Hemodynamics and Hemoacoustic Study on Abdominal Aortic Aneurysm: Effect of Asymmetry and pre-Aneurysm Curvature

A three-dimensional CFD study in Abdominal Aortic Aneurysms (AAA) is presented to investigate the effect of bulging asymmetry (β = 0.2, 0.5, and 1), bulging height (H/D = 2 and 3), and pre-aneurysm curvature (α = 0, 10⁰, 20⁰, and 40⁰) on sound signals detected through phonoangiography. Velocity fluctuation, sensed by a digital stethoscope is calculated using wall pressure data for pulsatile inlet flow at a Womersley number (Wo) of 16.5. Additionally, the risk of artery rupture and its variation with geometry is assessed, and a correlation between sound frequency and rupture-risk is proposed. Through the differentiation of vortices into vortex rings, contrails, and horse-shoe types, we explain the impact of flow structures on acoustic signals, which varies with the aneurysm geometry. Notably, aneurysms with higher asymmetry (β = 0.2) exhibit unstable vortex rings dissipating within the mid-aneurysm – causing pressure fluctuations. Conversely, aneurysms with high pre-aneurysm curvature (α = 40⁰) lack vortex rings, and instead, small contrails and horse-shoe vortices form in the pre-aneurysm region. Consequently, these structures create larger fluctuations, leading to higher cut-off frequencies in the sound signal. This research provides valuable insights into the relationship between AAA geometry and acoustic signals. Understanding the interplay of fluid dynamics and sound generation may aid in the diagnosis and risk assessment of AAA, improving patient outcomes.