Spiral/helical forms of blood flow have been observed in large arteries of the cardiovascular system, but their benefits remain underappreciated. Spiral flow has been postulated to improve near‐wall washout, promoting anti‐atherothrombotic conditions. This research aims to study the washout characteristics of spiral flow, specifically, its ability to increase velocity and wall shear stress (WSS) in atherothrombotic‐prone regions. Using 1.2 cm diameter angled test‐conduits (45°, 90°, 135°) with known recirculation/stasis regions at the bend corners, spiral flow washout potential was evaluated in terms of low velocity and low WSS. Two sub‐studies were conducted: the first utilized a spiral flow‐inducing device to enable qualitative analysis of washout‐potential in both computational fluid dynamic (CFD) simulations and benchtop ultrasound visualization; the second used CFD to study the impact of several induced helical wavelengths on the conduit‐dependent recirculation/stasis zones. Physical models of the angled conduits and spiral flow‐inducer were 3D‐printed to facilitate ultrasound visualization. Compared to straight flow, spiral flow generated by the flow‐inducer significantly cleared the recirculation/stasis zones at the corners of the angled conduits. CFD simulations demonstrated that past a geometry‐dependent threshold, increased helical content improved washout, denoted by decreased regions of low velocity and low WSS. Overall, spiral flow markedly improved washout in difficult to reach areas in the angled conduits. This has several important clinical implications: spiral flow shows great promise in reducing blood‐transport‐related complications and can be used to enhance the performance of future medical devices (eg grafts, mechanical circulatory support devices, hemodialysis access ports).
A three‐dimensional direct numerical simulation model coupled with the immersed boundary method has been developed to simulate a pulsatile flow in a planar channel with single and double one‐sided semicircular constrictions. For relevance to blood flow in large arteries, simulations have been performed at Reynolds numbers of 750 and 1000. Flow physics and resultant wall shear stress (WSS)‐based hemodynamic parameters are presented. The instantaneous vortex dynamics, mean flow characteristics, and turbulent energy spectra are evaluated for flow physics. Subsequently, three WSS‐based parameters, namely the time‐averaged WSS, oscillatory shear index, and relative residence time, are calculated over the stenotic wall and correlated with flow physics to identify the regions prone to atherosclerotic plaque progression. Results show that the double stenotic channel leads to high‐intensity and broadband turbulent characteristics downstream, promoting critical values of the WSS‐based parameters in the post‐stenotic areas. In addition, the inter‐space area between two stenoses displays multiple strong recirculations, making this area highly prone to atherosclerosis progression. The effect of stenosis degree on the WSS‐based parameters is studied up to 60% degree. As the degree of occlusion is increased, larger regions are involved with the nonphysiological ranges of the WSS‐based parameters.
more » « less- Award ID(s):
- 1936065
- PAR ID:
- 10361542
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Engineering Reports
- Volume:
- 4
- Issue:
- 1
- ISSN:
- 2577-8196
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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