Classification of Secondary Vortices in a Curved Pipe Model of an Artery
Open AccessThe prevalence and high morbidity of atherosclerosis have generated much interest, and a significant number of research efforts have been, and are currently being, dedicated to understanding the initiation and progression of atherosclerosis. Current hypotheses suggest that endothelial cells (ECs) are the gateway for atherogenesis and that their normal function in healthy vessels prevents the formation of atherosclerosis. ECs have the ability to respond to changes in wall shear stress (WSS) via a process known as mechano-transduction. Atherosclerotic plaque has been known to form in areas of low and oscillating WSS, in regions such as the inside of a bend. An experiment was designed to replicate conditions representative of those in a large human artery with matched viscosity, geometry, and driving waveform. Data were acquired with 2-D particle image velocimetry techniques at five streamwise locations around a 180° bend at 100 evenly-spaced instances in time across the 4 second period. In order to study the different parameters that affect the secondary flow patterns in arteries, five inlet flow waveforms were studied in addition to the physiological waveform. Important flow characteristics are identified and discussed as well as their potential influence on healthy artery function and on the progression of atherosclerosis. For each waveform, few coherent structures were observed in the secondary flow beyond the 90° measurement location, thus, presentation and analysis of results is focused on this location. At 90° coherent vortical structures for each case were observed to follow the same morphologies and evolution. The similar pattern of vortex evolution facilitated the development of a regime map which allows for prediction of secondary flow morphology based on parameters associated with the driving flow waveforms alone.
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