Large eddy simulation of pressure fluctuations inside stenosed blood vessels towards noninvasive diagnosis of atherosclerosis

Özden, Kamil
Atherosclerosis is a cardiovascular disease, in which plaque builds up inside a blood vessel, narrowing it down and forming a stenosis that adversely affects the flow. Because of the stenosis, turbulent flow occurs at the post-stenotic region, which causespressure fluctuations on the vessel wall. The resulting murmurpropogates through the surrounding tissue and reaches the skin surface. These sounds emitted from the stenosed vessels are evaluated as a sign of stenosis. In this study, large eddy simulations are conducted to investigate the turbulence- induced wall pressure fluctuations and resulting acoustic emission. In these simulations, the structures around the blood vessel are not modeled, the vessel wall is considered as rigid and only the flow inside the blood vessel is solved. Simulations are performed under both non-pulsatile and pulsatile flow conditions by using Newtonian and non-Newtonian fluid models. The two main parameters considered for this purpose are the stenosis severity and shape. The results show that stenosis severity under a certain level does not cause disturbance at the post- stenotic region. For stenoses above this critical level, increasing stenosis severity has an intensifying effect on the wall pressure fluctuations. Eccentric stenosis morphology causes more severe fluctuations than an axisymmetric one. Stenosis shape affects both the magnitude of fluctuations and the duration in which the pressure fluctuations are intense during the pulsatile cycle. Obtained pressure fluctuations are converted into sound and investigated in terms of sound levels and patterns. Sounds emitted from the blood vessels with different stenosis severities and shapes have different sound characteristics, and provide important information about the stenosis. Therefore, both the stenosis severity and shape must be taken into account to develop an acoustic-based diagnostic system.