Atherosclerosis is one of the most serious cardiovascular diseases that are present in mid-size and large-size arteries. Typically, it involves geometry of narrowing the arteries and hardening of the vessel wall due to the deposition of plaque. It is also known that it is primarily a progressive inflammatory disease initiated by a localized accumulation of low-density lipid (LDL) protein within the artery wall, potentially resulting in atherosclerotic constriction so-called arterial stenosis. This local restriction is common in arteries, that the presence of constriction in the artery results in unrecoverable head loss and the reduction of blood supply. It has been well-known that fluid dynamics and hemodynamics play a crucial role in the development and diagnosis of atherosclerosis in large arteries. In this study, we develop and perform direct numerical simulations (DNS), where a fractional-step method is used with a finite difference scheme. In addition, the immersed boundary method (IBM) is combined with DNS to simulate a flow around stenosed artery geometry. This coupled DNS and IBM method can be a benchmark to simulate pulsatile blood flow in a nearly realistic blood vessel with irregular and deformable stenosis. In particular, we focus on a pulsatile flow in planar channel geometry with single or double stenosis of a semicircular shape at Reynolds numbers of 750 and 1000. Both Reynolds numbers are within the range of typical blood flows in human large-arteries, such as coronary, carotid, and femoral arteries. It is of significantly importance in terms of both fluid dynamics and hemodynamic parameters. Here, we first evaluate fluid-dynamic properties, including vortex structure at each phase of the pulsatile cycle and averaged streamlines to characterize the mean flow. Then, the near-wall hemodynamic parameters, including time-averaged wall shear stress (TAWSS), oscillatory shear index (OSI), and relative residence time (RRT), are computed to characterize the critical locations with regard to atherosclerosis development. The fluid-dynamic and hemodynamic properties of double stenosis are compared to those with single stenosis. The presence of a pair of stenoses leads to an increase in the flow disturbance and the disintegration of shear layers at the post-stenotic region, strengthening the characterized recirculation zone in this region. The most apparent impact of double stenosis is observed in an inter-space area, where multiple recirculations occurs. This inter-space region is likely to be prone to atherosclerotic plaque development as it is the area associated with strongly oscillatory wall shear stress and high RRT. Lastly, we evaluate the effect of stenosis degree on HWPs.


Direct Numerical Simulation of Pulsatile Flow Around Single or Double Stenosis Using Immersed Boundary Method

Division / Sponsors: 
Aerospace, Bioengineering, Applied Mechanics, Design Engineering Division, Advanced Energy Systems, Manufacturing Engineering Division, Noise Control and Acoustics, Nondestructive Evaluation, Diagnosis, and Prognosis (NDPD), Nuclear Engineering Division, Process Industries Division, Fluids Engineering, Heat Transfer, Materials, Microelectromechanical Systems, Safety Engineering and Risk Analysis, Computers & Information in Engineering


Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2020/volume/84478

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