Effect Of non-Newtonian Viscosity Research Articles

Artificial neural networks strategy to analyze the magnetohydrodynamics Casson-Maxwell nanofluid flow through the cone and disc system space

The Casson-Maxwell model is particularly useful for studying viscoplastic fluids or fluids with yield stress, making it applicable to various engineering applications, including extrusion processes, coating applications, and biomedical fluid dynamics. Casson-Maxwell fluid flow enhances mass transfer rates due to the combined effects of non-Newtonian viscosity and viscoelastic behavior. This is particularly useful in processes where mass transfer limitations play a significant role, such as in multiphase reactions or reactive distillation systems. In the context of the above applications the present model, is the combination of Casson- Maxwell fluids that flow through the varying gap of the spinning cone and disk system (CDS) for the heat transfer enhancement. The magnetic field is also imposed in the upright direction to the flow field. The solution of the transform equations has been obtained through artificial neural networks (ANN). The skin friction, heat transfer rate, and comparative analysis have been done. The Casson-Maxwell parameters that depend on the viscoelastic behavior and high viscosity term, causes the fluid to slow down and tends to store the temperature, for a long time as compared to traditional fluids. The radial component of velocity decreases due to the increase in magnetic field. The relative error of the reference and targeted dates is calculated to demonstrate the best precision efficiency of ANN, with a range of 10−3 to 10−4.

Effects of non-Newtonian viscosity on arterial and venous flow and transport

It is well known that blood exhibits non-Newtonian viscosity, but it is generally modeled as a Newtonian fluid. However, in situations of low shear rate, the validity of the Newtonian assumption is questionable. In this study, we investigated differences between Newtonian and non-Newtonian hemodynamic metrics such as velocity, vorticity, and wall shear stress. In addition, we investigated cardiovascular transport using two different approaches, Eulerian mass transport and Lagrangian particle tracking. Non-Newtonian solutions revealed important differences in both hemodynamic and transport metrics relative to the Newtonian model. Most notably for the hemodynamic metrics, in-plane velocity and vorticity were consistently larger in the Newtonian approximation for both arterial and venous flows. Conversely, wall shear stresses were larger for the non-Newtonian case for both the arterial and venous models. Our results also indicate that for the Lagrangian metrics, the history of accumulated shear was consistently larger for both arterial and venous flows in the Newtonian approximation. Lastly, our results also suggest that the Newtonian model produces larger near wall and luminal mass transport values compared to the non-Newtonian model, likely due to the increased vorticity and recirculation. These findings demonstrate the importance of accounting for non-Newtonian behavior in cardiovascular flows exhibiting significant regions of low shear rate and recirculation.

The Influence of Womersley Number on Non-Newtonian Effects: Transient Computational Study of Blood Rheology

Abstract A properly validated computational fluid dynamics methodology is a valuable predictive tool capable of aiding in the development of new methods for treating cardiovascular disease (CVD). Although blood is a shear-thinning non-Newtonian fluid, a key assumption that remains highly contested is whether non-Newtonian blood can be approximated as a Newtonian fluid. Previously, a preliminary link was established between the effects of non-Newtonian viscosity and the Womersley number, α, which could lend an explanation to the varied conclusions from previous comparison studies. Building upon this foundation, computational fluid dynamics was utilized to perform an in-depth investigation into the link between blood rheology and α for multiple geometries. For the first time in the open literature, the present research sheds definitive light on the source of the diverse results from previous studies. It demonstrates how α can affect the severity of non-Newtonian effects when compared to Newtonian viscosity, while otherwise maintaining the same boundary conditions. These results show that an increase in α reduces the peak global importance factor, a measure of the difference between Newtonian and non-Newtonian models, by upwards of 90%. Additionally, this results in a decrease in the relative difference for disturbed flow factors, parameters linked to the initiation and progression of CVD, from upwards of 34% down to approximately 5%. This study proves that there is a significant relationship between α and blood rheology, with higher α shifting the apparent viscosity of non-Newtonian models further toward the constant Newtonian viscosity.

Computational analysis of one-dimensional models for simulation of blood flow in vascular networks

The paper is devoted to the comparison of one-dimensional models, used for the simulation of blood flow in elastic vessels. The inviscid, Newtonian, and non-Newtonian models of blood are considered. The one-dimensional non-Newtonian models, corresponding to widely-used rheological models with shear-dependent viscosity (Power Law, Carreau, Carreau–Yasuda, Cross, simplified Cross, modified Cross, Powell–Eyring, modified Powell–Eyring, Yeleswarapu, modified Yeleswarapu, and Quemada) are presented.The attention is focused on the investigation of the influence of viscosity, shape factor, velocity profile, non-Newtonian viscosity, and hematocrit. In the numerical experiments, the models of arterial systems with twenty and thirty-seven vessels are considered. It is demonstrated, that for the vessels near the heart the effect of viscosity can be considered as inessential, and an inviscid model can be used. The main effect on the relative deviations of solutions, obtained by different models, is realized by the velocity profile. The effect of non-Newtonian viscosity is not so essential, but can be taken into account for the models with peripheral vessels.

The effect of non-Newtonian viscosity on the stability of the Blasius boundary layer

We consider, for the first time, the stability of the non-Newtonian boundary layer flow over a flat plate. Shear-thinning and shear-thickening flows are modelled using a Carreau constitutive viscosity relationship. The boundary layer equations are solved in a self-similar fashion. A linear asymptotic stability analysis, that concerns the lower-branch structure of the neutral curve, is presented in the limit of large Reynolds number. It is shown that the lower-branch mode is destabilised and stabilised for shear-thinning and shear-thickening fluids, respectively. Favourable agreement is obtained between these asymptotic predictions and numerical results obtained from an equivalent Orr-Sommerfeld type analysis. Our results indicate that an increase in shear-thinning has the effect of significantly reducing the value of the critical Reynolds number, this suggests that the onset of instability will be significantly advanced in this case. This postulation, that shear-thinning destabilises the boundary layer flow, is further supported by our calculations regarding the development of the streamwise eigenfunctions and the relative magnitude of the temporal growth rates.

Modeling Blood Flow Through Intracranial Aneurysms: A Comparison of Newtonian and Non-Newtonian Viscosity

The effect of non-Newtonian blood flow on the value of wall shear stress (WSS) of an intracranial aneurysm was investigated using computational fluid dynamics. For cerebral arteries, blood is often assumed to behave as a Newtonian fluid, though the effects of non-Newtonian flow on the prediction of areas of low WSS associated with aneurysm rupture are not clear. Geometry was based on published data and a Newtonian model validated against experimental results. Newtonian, unrestricted non-Newtonian, and viscosity-limited non-Newtonian models were compared under pulsatile conditions. Peak WSS of the Newtonian model was 28.7 Pa, and the lowest value of peak WSS for the unrestricted non-Newtonian models was 16.5 Pa. Viscosity-limited non-Newtonian models predicted flow velocity and WSS similar to those predicted by the Newtonian model in high-shear-rate regions, though maximum areas of critically low WSS were up to 42 % smaller than those predicted by the Newtonian model. In conclusion, viscosity limits are required to prevent excessive thinning of non-Newtonian models and the effects of non-Newtonian viscosity are significant for blood flow within low-shear-rate regions of an intracranial aneurysm.

Effects of Non-Newtonian Viscosity on the Hemodynamics of Cerebral Aneurysms

The purpose of this study is to present a comparative study between Newtonian and non-Newtonian blood viscosity models for simulating the hemodynamic wall shear stress (WSS) of cerebral aneurysms. The non-Newtonian blood viscosity was modeled using the Carreau-Yasuda nonlinear model. Two realistic cerebral aneurysm models, derived from 3D angiography imaging, were studied and simulated via computational fluid dynamics solver based on finite volume method, with a pulsating sinusoidal waveform boundary conditions. The maximum wall shear stresses were found at the aneurysm’s neck and apex, the inlet arteriole recorded an average wall shear stress and as for the blebs and tips the wall shear stress values were remarkably low. The comparison indicated that non-Newtonian blood viscosity model predicted a lower range of WSS than of the Newtonian model, which provides more accuracy for simulating aneurysm hemodynamics.

Effect of non-Newtonian viscosity on the fluid-dynamic characteristics in stenotic vessels

Although blood is known to have shear-thinning and viscoelastic properties, the effects of such properties on the hemodynamic characteristics in various vascular environments are not fully understood yet. For a quantitative hemodynamic analysis, the refractive index of a transparent blood analogue needs to be matched with that of the flowing conduit in order to minimize the errors according to the distortion of the light. In this study, three refractive index-matched blood analogue fluids with different viscosities are prepared—one Newtonian and two non-Newtonian analogues—which correspond to healthy blood with 45 % hematocrit (i.e., normal non-Newtonian) and obese blood with higher viscosity (i.e., abnormal non-Newtonian). The effects of the non-Newtonian rheological properties of the blood analogues on the hemodynamic characteristics in the post-stenosis region of an axisymmetric stenosis model are experimentally investigated using particle image velocimetry velocity field measurement technique and pathline flow visualization. As a result, the centerline jet flow from the stenosis apex is suppressed by the shear-thinning feature of the blood analogues when the Reynolds number is smaller than 500. The lengths of the recirculation zone for abnormal and normal non-Newtonian blood analogues are 3.67 and 1.72 times shorter than that for the Newtonian analogue at Reynolds numbers smaller than 200. The Reynolds number of the transition from laminar to turbulent flow for all blood analogues increases as the shear-thinning feature increases, and the maximum wall shear stresses in non-Newtonian fluids are five times greater than those in Newtonian fluids. However, the shear-thinning effect on the hemodynamic characteristics is not significant at Reynolds numbers higher than 1000. The findings of this study on refractive index-matched non-Newtonian blood analogues can be utilized in other in vitro experiments, where non-Newtonian features dominantly affect the flow characteristics.

Non-Newtonian and flow pulsatility effects in simulation models of a stented intracranial aneurysm

Three models of different stent designs implanted in a cerebral aneurysm, originating from the Virtual Intracranial Stenting Challenge '07, are meshed and the flow characteristics simulated using commercial computational fluid dynamics (CFD) software in order to investigate the effects of non-Newtonian viscosity and pulsatile flow. Conventional mass inflow and wall shear stress (WSS) output are used as a means of comparing the CFD simulations. In addition, a WSS distribution is presented, which clearly discriminates in favour of the stent design identified by other groups. It is concluded that non-Newtonian and pulsatile effects are important to include in order to avoid underestimating wss, to understand dynamic flow effects, and to discriminate more effectively between stent designs.

Non-modal instability in plane Couette flow of a power-law fluid

In this paper, we study the linear stability of a plane Couette flow of a power-law fluid. The influence of shear-thinning effect on the stability is investigated using the classical eigenvalue analysis, the energy method and the non-modal stability theory. For the plane Couette flow, there is no stratification of viscosity. Thus, for the stability problem the stress tensor is anisotropic aligned with the strain rate perturbation. The results of the eigenvalue analysis and the energy method show that the shear-thinning effect is destabilizing. We focus on the effect of non-Newtonian viscosity on the transition from laminar flow towards turbulence in the framework of non-modal stability theory. Response to external excitations and initial conditions has been studied by examining the ε-pseudospectrum and the transient energy growth. For both Newtonian and non-Newtonian fluids, it is found that there can be a rather large transient growth even though the linear operator of the Couette flow has no unstable eigenvalue. The results show that shear-thinning significantly increases the amplitude of response to external excitations and initial conditions.

304 複合ジェットの安定性に及ぼす非ニュートン粘性の効果(OS-2 熱流体力学における非線形現象の解析・制御(2))

304 複合ジェットの安定性に及ぼす非ニュートン粘性の効果(OS-2 熱流体力学における非線形現象の解析・制御(2))

Non-modal instabilities of two-dimensional disturbances in plane Couette flow of a power-law fluid

Instabilities of fluid flows have traditionally been investigated by normal mode analysis, i.e. by linearizing the equations of flow and testing for unstable eigenvalues of the linearized problem. However, the results of eigenvalue analysis agree poorly in many cases with experiments, especially for shear flows. In this paper we study the instabilities of two-dimensional Couette flow of a polymeric fluid in the framework of non-modal stability theory rather than normal mode analysis. A power-law model is used to describe the polymeric liquid. We focus on the response to external excitations and initial conditions by examining the pseudospectra structures and the transient energy growths. For both Newtonian and non-Newtonian flows, the results show that there can be a rather large transient growth even though the linear operator of Couette flow has no unstable eigenvalue. The effects of non-Newtonian viscosity on the transient behaviors are examined in this study. The results show that the “shear-thinning/shear-thickening” effect increases/decreases the amplitude of responses to external excitations and initial conditions.

Beyond the Virtual Intracranial Stenting Challenge 2007: Non-Newtonian and flow pulsatility effects

The Virtual Intracranial Stenting Challenge 2007 (VISC’07) is becoming a standard test case in computational minimally invasive cerebrovascular intervention. Following views expressed in the literature and consistent with the recommendations of a report, the effects of non-Newtonian viscosity and pulsatile flow are reported. Three models of stented cerebral aneurysms, originating from VISC’07 are meshed and the flow characteristics simulated using commercial computational fluid dynamics (CFD) software. We conclude that non-Newtonian and pulsatile effects are important to include in order to discriminate more effectively between stent designs.

Effects of surface geometry and non-newtonian viscosity on the flow field in arterial stenoses

Hemodynamics including flow pattern, shear stress, and blood viscosity characteristics has been believed to affect the development and progression of arterial stenosis, but previous studies lack of realistic physiological considerations such as irregular surface geometry, non-Newtonian viscosity characteristics and flow pulsatility. The effects of surface irregularities and non-Newtonian viscosity on flow fields were explored in this study using the arterial stenosis models with 48% arterial occlusions under physiological flow condition. Computational flow dynamics based on the finite volume method was employed for Newtonian and non-Newtonian fluid. The wall shear stresses (WSS) in the irregular surface model were higher compared to those in the smooth surface models. Also, non-Newtonian viscosity characteristics increase the peak WSS significantly. The dimensionless pressure drop and the time averaged WSS in pulsatile flow were higher than those in steady flow. But pulsatility effects on pressure and WSS were less significant compared to non-Newtonian viscosity effects. Therefore, irregular surface geometry and non-Newtonian viscosity characteristics should be considered in predicting pressure drop and WSS in stenotic arteries.

EXACT ANALYSIS OF UNSTEADY CONVECTIVE DIFFUSION IN A SIMPLIFIED CROSS MODEL FLUID

The article presents the effect of non-Newtonian viscosity on the longitudinal dispersion of tracer molecules released in an incompressible viscous non-Newtonian fluid (known as the simplified Cross model fluid) under the action of a constant pressure gradient. The Gill and Sankarasubramanian model is used to solve the unsteady convection diffusion equation for all time periods. An exact expression is obtained for the longitudinal convection coefficient K 1(η*), which shows the effect of the non-Newtonian parameter η* on the centerline coefficient. It is seen that the value of the K 1(η*) for η* > 1 is always smaller than the corresponding value for a Newtonian fluid. Also, the longitudinal dispersion coefficient of the solute K 2(τ, η*) is determined exactly. The results show that the K 2(τ, η*) asymptotically reaches a stationary state after a certain time. The effect of the η* on the most dominant dispersion coefficient is clearly depicted. Finally, the axial distribution of the average concentration θ m of the solute over the channel cross section is determined at a fixed instant after the solute injection for several values of the η*. The results for “pure convection” are also reported

Effect of non-newtonian viscosity for surfactant solutions on vortex characteristics in a swirling pipe flow

Effects of non-Newtonian viscosity for surfactant solution on the vortex characteristics and drag-reducing rate in a swirling pipe flow are investigated by pressure drop measurements, velocity profile measurements and viscosity measurements. Non-Newtonian viscosity is represented by power-law model (τ=kDn). Surfactant solution used has shear-thinning viscosity with n<1.0. The swirling flow in this study has decay of swirl and vortex-type change from Rankin’s combined vortex to forced vortex. It is shown that the effect of shear-thinning viscosity on the decay of swirl intensity is different by vortex category and the critical swirl number with the vortex-type change depends on shear-thinning viscosity.

Dip coating of dielectric and solder mask epoxy polymer layers for build-up purposes

Polymer coatings used as build-up layers in advanced printed circuit boards (PCBs) are usually applied through curtain coating or lamination for industrial purposes. Dip coating can be used as an easier and cheaper way of applying a build-up layer, in particular for research purposes, because of the relative high viscosity of liquid polymer solutions used for build-up layers or solder mask layers. The thickness of the deposited layer is examined on different substrates and can be varied with great ease and small variance by changing the pull-out speed. The experimental thickness of the coated layer is compared to various models existing in literature. The deposited polymer layers show a thickening effect in comparison to the Landau and Levich theory. This thickening effect depends on the properties of the polymer solution and the substrate on which the polymer layer is applied. The coated thickness of polymer solutions is influenced by a number of phenomena, such as normal stresses, non-Newtonian viscosity effects and influences of gravity. More practical empirical thickness models are developed and fitted. Polymer solutions containing inorganic filler particles show a different coating behavior in comparison to polymer solutions containing no filler particles.

Dean Vortex Membrane Microfiltration Non-Newtonian Viscosity Effects

Many industrial feeds behave as non-Newtonian fluids, and little understanding exists as to their influence on cross-flow microfiltration (CMF) performance. The viscosity effects of a model non-Newtonian shear-thickening fluid were investigated in CMF with and without suspended silica particles in the feed. The goals were to compare the performance of Dean vortex filtration for non-Newtonian fluids with that for Newtonian fluids and, using a shear-thickening fluid, to establish, in a negative control experiment for equivalent axial flow rates, that the mean wall shear rates is higher in helical tube flow than in linear tube flow. Hence, the effect of viscosity on the formation of controlled centrifugal instabilities (Dean vortices) was studied. Non-Newtonian behavior was imparted to the fluid through the addition of a cationic surfactant, tetradecyltrimethylammonium salicylate (TTASal), that could freely permeate the membrane and that exhibited little noticeable fouling. Because the membrane did not retain the micelles and freely passed the surfactant monomer, fouling behavior could be separately studied by adding silica particles to the micellar solution. Results were compared with a previously studied Newtonian system for both linear and helical CMF. Two new mass transfer correlations were obtained for a shear-thickening surfactant solution in the presence of a 0.1 w/w % silica concentration for laminar flow in linear (no vortices) and helical (with vortices) membrane pipes. The viscosity was described as a function of surfactant concentration and velocity. The correlation for Dean vortex laminar flow incorporated the effect of increasing viscosity on the stability of Dean vortices by adjusting the exponent of the Reynolds number in the expression Shhel = 0.19(a/rc)0.07Re[0.55(η(v=0)/η(v=v))]Sc0.33 for Re < 800.

The flow of blood in tubes: theory and experiment

The paper is devoted to the comparison of one-dimensional models, used for the simulation of blood flow in elastic vessels. The inviscid, Newtonian, and non-Newtonian models of blood are considered. The one-dimensional non-Newtonian models, corresponding to widely-used rheological models with shear-dependent viscosity (Power Law, Carreau, Carreau–Yasuda, Cross, simplified Cross, modified Cross, Powell–Eyring, modified Powell–Eyring, Yeleswarapu, modified Yeleswarapu, and Quemada) are presented.The attention is focused on the investigation of the influence of viscosity, shape factor, velocity profile, non-Newtonian viscosity, and hematocrit. In the numerical experiments, the models of arterial systems with twenty and thirty-seven vessels are considered. It is demonstrated, that for the vessels near the heart the effect of viscosity can be considered as inessential, and an inviscid model can be used. The main effect on the relative deviations of solutions, obtained by different models, is realized by the velocity profile. The effect of non-Newtonian viscosity is not so essential, but can be taken into account for the models with peripheral vessels.

Studies of Blood Flow in Arterial Bifurcations Using Computational Fluid Dynamics

The local blood flow in arteries, especially at bends and bifurcations, is correlated with the distribution of atherosclerotic lesions. The flow is three-dimensional, unsteady and difficult to measure in vivo. In this paper a numerical treatment of blood flow in general three-dimensional arterial bifurcations is presented. The flow is assumed to be laminar and incompressible, the blood non-Newtonian and the vessel wall rigid. The three-dimensional time-dependent Navier-Stokes equations are employed to describe the flow, and a newly developed computational fluid dynamics (CFD) code AST EC based on finite volume methods is used to solve the equations. A comprehensive range of code validations has been carried out. Good agreement between numerical predictions and in vitro model data is demonstrated, but the correlation with in vivo measurements is less satisfactory. Effects of the non-Newtonian viscosity have also been investigated. It is demonstrated that differences between Newtonian and non-Newtonian flows occur mainly in regions of flow separation. With the non-Newtonian fluid, the duration of flow separation is shorter and the reverse flow is weaker. Nevertheless, it does not have significant effects on the basic features of the flow field. As for the magnitude of wall shear stress, the effect of non-Newtonian viscosity might not be negligible.