Non-Newtonian perspectives on pulsatile blood-analog flows in a 180° curved artery model

Abstract

Complex, unsteady fluid flow phenomena in the arteries arise due to the pulsations of the heart that intermittently pumps the blood to the extremities of the body. The many different flow waveform variations observed throughout the arterial network are a result of this process and a function of the vessel properties. Large scale secondary flow structures are generated throughout the aortic arch and larger branches of the arteries. An experimental 180° curved artery test section with physiological inflow conditions was used to validate the computational methods implemented in this study. Good agreement of the secondary flow structures is obtained between experimental and numerical studies of a Newtonian blood-analog fluid under steady-state and pulsatile, carotid artery flow rate waveforms. Multiple vortical structures, some of opposite rotational sense to Dean vortices, similar to Lyne-type vortices, were observed to form during the systolic portion of the pulse. Computational tools were used to assess the effect of blood-analog fluid rheology (i.e., Newtonian versus non-Newtonian). It is demonstrated that non-Newtonian, blood-analog fluid rheology results in shear layer instabilities that alter the formation of vortical structures during the systolic deceleration and onwards during diastole. Additional vortices not observed in the Newtonian cases appear at the inside and outside of the bend at various times during the pulsation. The influence of blood-analog shear-thinning viscosity decreases mean pressure losses in contrast to the Newtonian blood analog fluid.

Are Non-Newtonian Effects Important in Hemodynamic Simulations of Patients With Autogenous Fistula?

“…The choice of non-Newtonian model may be based on several factors. In the present case, where patient-specific viscometry data are available, the preferred model is one which (1) was developed specifically, or at least has been adapted, for blood's rheological parameters, such as hematocrit, (2) contains the minimum number of parameters that facilitate a good fit to the actual viscosity data [16], and (3) are amenable to implementation in a CFD code. The model that best meets these criteria is that due to Quemada [28,31,32].…”

“…On the other hand, Refs. [7] and [10][11][12][13] are all in favor of using the Newtonian flow assumption, while many others [14][15][16][17][18][19][20][21][22][23][24][25] highlight the differences between the two assumptions in various different scenarios.…”

Experimental and numerical investigation of a pulsatile flow field in an S-shaped exhaust pipe of an automotive engine

“…Timité et al (2010) reported that the secondary flow intensity increases with the appearance of the Lyne-type vortices. More recently, the complex secondary flow structures, consisting of multiple vortices in addition to the Dean and Lyne types, were investigated under physiological pulsatile conditions both through experiments and numerical simulations (Glenn et al, 2012;van Wyk et al, 2015). Whereas most studies on pulsatile bend flows were restricted to laminar cases, Kalpakli et al (2011Kalpakli et al ( , 2013 measured three velocity components of the pulsatile turbulent flow in the cross section of a 90° bend with the technique of stereoscopic PIV.…”

Shannon Entropy-Based Wavelet Transform Method for Autonomous Coherent Structure Identification in Fluid Flow Field Data

“…The vessel diameter in our case (12.7 × 10 −3 m) is much larger than the corpuscular scale, and therefore, the Newtonian assumptions in the core regions of the blood vessels are fairly adequate. However, at the near-wall regions, shear-thinning effects may persist that lead to alterations of the near-wall shear stresses, as shown in our recent publication, van Wyk et al [41]. Since the secondary flow characteristics that we are studying fall fairly well within the core regions of the flow, the Newtonian blood assumptions are valid.…”