A Numerical and Experimental Investigation of Transitional Pulsatile Flow in a Stenosed Channel

Abstract

In the present paper, a closely coupled numerical and experimental investigation of pulsatile flow in a prototypical stenotic site is presented. Detailed laser Doppler velocimetry measurements upstream of the stenosis are used to guide the specification of velocity boundary conditions at the inflow plane in a series of direct numerical simulations (DNSs). Comparisons of the velocity statistics between the experiments and DNS in the post-stenotic area demonstrate the great importance of accurate inflow conditions, and the sensitivity of the post-stenotic flow to the disturbance environment upstream. In general, the results highlight a borderline turbulent flow that sequentially undergoes transition to turbulence and relaminarization. Before the peak mass flow rate, the strong confined jet that forms just downstream of the stenosis becomes unstable, forcing a role-up and subsequent breakdown of the shear layer. In addition, the large-scale structures originating from the shear layer are observed to perturb the near wall flow, creating packets of near wall hairpin vortices.

CFD analysis of pulsatile blood flow in an atherosclerotic human artery with eccentric plaques

“…Results, not far from Newtonian cases, focus on transition from stable to unstable flow once Bingham and Reynolds numbers are assigned. Beratlis et al (2005) merges experimental (Doppler) and numerical approaches to correlate blood flow field upstream and downstream of a stenosis. In Lorenzini (2005), instead, a GPL code is used to simulate coronary blood flow as affected by an intravascular Doppler catheter; among the rheologies tested, results show that the two-phase nature of blood requires a nonNewtonian (Cassonian) description to well consider the shear stress effect.…”

Numerical analysis of the effect of turbulence transition on the hemodynamic parameters in human coronary arteries

“…Some assumed the blood flow in coronary arteries to be laminar (7)(8)(9)(10)(11)(12)(13)(14) and behave as Newtonian fluid (8,(15)(16)(17) and some studied turbulence transition and non-Newtonian effects considering idealized straight arterial model with single model stenosis obstruction (11,15,(17)(18)(19)(20)(21). Several experimental investigations have been carried out on flow disturbances in the downstream region of idealized modeled stenosis (18,22,23). Ahmed and Giddens (24) examined the development of flow disturbances downstream of smooth 25%, 50% and 75% area reductions in an idealized geometry and observed a substantial increase in the disturbance level above 50% stenosis.…”

“…Ahmed and Giddens (24) examined the development of flow disturbances downstream of smooth 25%, 50% and 75% area reductions in an idealized geometry and observed a substantial increase in the disturbance level above 50% stenosis. Beratlis et al (18) conducted both numerical and experimental investigation of transitional pulsatile flow in a prototypical stenotic site giving a blockage ratio of 50% and Reynolds number of 570. They used direct numerical simulations (DNS) to study the flow disturbances downstream of the constriction and observed that distal region is dominated by alternating random fluctuations.…”

Influence of different bell-shaped stenoses on the progression of the disease, atherosclerosis

“…The consideration of turbulent flow in the pulsatile form has been studied by Varghese and Frankel [24] with both cosine and trapezoidal shaped stenosis. A numerical and experimental investigation of transitional pulsatile flow in a circular shaped stenosed channel has been carried by Beratlis et al [25]. Sherwin and Blackburn [26] have studied the threedimensional instabilities and transition to turbulence of steady flow, steady flow plus an oscillatory component, and an idealized vascular pulsatile flow in a tube with a smooth axisymmetric sinusoidal constriction.…”