The influence of inlet velocity profile and secondary flow on pulsatile flow in a model artery with stenosis

Abstract

The results of an experimental investigation to determine the influence of two physiologically relevant inlet conditions on the flow physics downstream of an idealized stenosis are presented. The two inlet conditions are an asymmetric mean inlet velocity profile and an asymmetric mean inlet velocity profile plus secondary flow, as found downstream of a bend. The stenosis is modelled as an axisymmetric 75 % area reduction occlusion with a length-to-diameter ratio of 2. The flow was forced by a 10-harmonic carotid artery-inspired waveform with mean, maximum and minimum Reynolds numbers of 364, 1424 and 24, respectively, and a Womersley number of 4.6. Laser Doppler velocimetry and particle image velocimetry were used to characterize the spatial and temporal evolution of a baseline case (no disturbances) as well as the two physiologically relevant inlet conditions. The asymmetric inlet velocity profile was found to reduce the region of influence of the stenosis by forcing the stenotic jet towards the tube wall via an induced non-uniform radial pressure gradient, similar to the Coanda effect. Curvature-induced secondary flow was found to play a minor role in the near-stenosis region. Vortex ring formation was relatively unaffected by the mean velocity gradient and secondary flow. Evidence of remnants of the starting vortex ring was observed far downstream in all cases. † Present address:

Secondary flow structures under stent-induced perturbations for cardiovascular flow in a curved artery model

“…The seeding particles had a density of 1.05 kg/cm 3 . Peterson and Plesniak (2008) found that the secondary flow patterns in the circular bend strongly depend on the forcing flow waveform. The physiological flow waveform used in this study is based on ultrasound and ECG measurements of blood flow made by Holdsworth et al (1999) within the left and right carotid arteries of 17 healthy human volunteers.…”

Effect of small asymmetries on axisymmetric stenotic flow

“…A number of studies have investigated the effect on stenotic flow of nonaxisymmetric perturbations to the geometry (Varghese et al 2007) and the inlet velocity profile (Peterson & Plesniak 2008). Peterson & Plesniak (2008) investigated experimentally the effect on stenotic flow of skewed velocity profiles and secondary flow generated by a pipe bend on the main flow features, however on pulsatile stenotic flow.…”

“…Peterson & Plesniak (2008) investigated experimentally the effect on stenotic flow of skewed velocity profiles and secondary flow generated by a pipe bend on the main flow features, however on pulsatile stenotic flow. They found that a strong skewing of the velocity profile of the pulsatile inlet significantly reduced the extent of the stenotic jet, forcing it towards the pipe wall.…”

Analytic solutions of Newtonian and non-Newtonian pipe flows subject to a general time-dependent pressure gradient

“…More recently, Agarwal et al [29] studied pulsatile flow in carotid artery bifurcation, and Peterson and Plesniak [30] experimentally studied the influence of inlet velocity profile and secondary flow on pulsatile flow in a model artery with stenosis. Ünsal [31] carried out a combined analytical and experimental investigation of sinusoidal mass-flow controlled, pulsating pipe flow, discussing deviations of the analytic solution from the experimental as the Reynolds number increased.…”