A variant of Stokes’ second problem for a new shear thinning model for paint

The mathematical model of electrorheological fluid damper which is based on the flow mode has been proposed in many articles. In this paper, a new optimization model of the giant electrorheological fluid damper, which is based on the shear thinning mathematical model, is proposed and simulated numerically with Matlab. The mathematical model of giant electrorheological fluid damper without considering the shear thinning model is also simulated numerically in this paper. The data of the damping force-excitation displacement of the damper are tested by the 810 Material Test System. By comparing the simulated data with the experimental data, it can be seen that the model considering the shear thinning mode can predict the damping force that the damper can produce.

Viscoelastic fluids can be difficult to model due to the wide range of different physical behaviors that polymer melts can exhibit. One such feature is the viscous elastic boundary layer. We address the particular problem of a viscoelastic shear-dependent fluid flowing past a corner and investigate how the properties of the boundary layer change for a White-Metzner fluid. The boundary layer equations are derived and the upstream layer is matched with the far-field flow. It was found that if the fluid is sufficiently shear thinning then the viscoelastic boundary layer formulation fails due to the inertial forces becoming dominant. The depth of the boundary layer is controlled by the shear-thinning parameters. These effects are not a feature of other shear-thinning models, such as the Phan-Thien-Tanner model. This study provides insight in the different effects of some commonly used viscoelastic models in corner flows in the upstream boundary layer, the downstream boundary layer is not addressed.

Simulations were performed to determine the magnitude and types of errors one can expect when approximating blood in large arteries as a Newtonian fluid, particularly in the presence of secondary flows. This was accomplished by running steady simulations of blood flow in straight and curved tubes using both Newtonian and shear-thinning viscosity models. In the shear-thinning simulations, the viscosity was modeled as a shear rate-dependent function fit to experimental data. Simulations in straight tubes were modeled after physiologically relevant arterial flows, and flow parameters for the curved tube simulations were chosen to examine a variety of secondary flow strengths. The diameters ranged from 1 mm to 10 mm and the Reynolds numbers from 24 to 1500. Pressure and velocity data are reported for all simulations. In the straight tube simulations, the shear-thinning flows had flattened velocity profiles and higher pressure gradients compared to the Newtonian simulations. In the curved tube flows, the shear-thinning simulations tended to have blunted axial velocity profiles, decreased secondary flow strengths, and decreased axial vorticity compared to the Newtonian simulations. The cross-sectionally averaged pressure drops in the curved tubes were higher in the shear-thinning flows at low Reynolds number but lower at high Reynolds number. The maximum deviation in secondary flow magnitude averaged over the cross sectional area was 19% of the maximum secondary flow and the maximum deviation in axial vorticity was 25% of the maximum vorticity.

We study the rheometrical and complex flow response of the double-convection-reptation (DCR) model with chain stretch proposed recently by Ianniruberto and Marrucci (2002) for entangled linear polymers. The single- and two-mode differential versions of the model are used, with the parameter values identified by Ianniruberto and Marrucci (2002) for a nearly monodisperse polybutadiene solution. These authors found that the DCR model with stretch predicts the rheometrical shear behavior of the fluid well in the modest experimental range of deformation rates. Our calculations for the higher shear rates reached in simulations of complex flow reveal anomalous or questionable behavior, namely, shear thickening over an intermediate range of shear rates and large chain stretch in fast shear flows. This behavior is shown to be shared by the original integro-differential DCR theory, of which the differential DCR model is actually a mathematical approximation. We also show that the original DCR theory with stretch predicts excessive shear thinning at high shear rates, while its differential approximation remains stable for all shear rates. Using the backward-tracking Lagrangian particle method [Wapperom et al. (2000)], we investigate the response of the differential DCR model in start-up flow through an axisymmetric contraction/expansion geometry. We compare the single- and two-mode model predictions (in terms of the steady-state vortex structure, chain stretch, and overall pressure drop), and correlate these with the steady and start-up rheometrical responses in shear and extension. Significant chain stretch is predicted in the vicinity of the axis of symmetry and in thin boundary layers located at the constriction wall. As a result, the DCR predictions significantly depart from the stress-optical rule in these flow regions. Chain stretch also affects the flow kinematics, with the appearance of a large upstream steady-state vortex. Surprisingly, however, the predicted pressure drop is not affected much by these kinematical changes, and is qualitatively described by a simple inelastic, shear-thinning model.

Sedimentation of a sphere near a vertical wall in an Oldroyd-B fluid

To elucidate the difference between Newtonian and shear thinning non-Newtonian assumptions of blood in the analysis of DES drug delivery, we numerically simulated the local flow pattern and the concentration distribution of the drug at the lumen-tissue interface for a structurally simplified DES deployed in a curved segment of an artery under pulsatile blood flow conditions. The numerical results showed that when compared with the Newtonian model, the Carreau (shear thinning) model could lead to some differences in the luminal surface drug concentration in certain areas along the outer wall of the curved vessel. In most areas of the vessel, however, there were no significant differences between the 2 models. Particularly, no significant difference between the two models was found in terms of the area-averaged luminal surface drug concentration. Therefore, we believe that the shear thinning property of blood may play little roles in DES drug delivery. Nevertheless, before we draw the conclusion that Newtonian assumption of blood can be used to replace its non-Newtonian one for the numerical simulation of drug transport in the DES implanted coronary artery, other more complex mechanical properties of blood such as its thixotropic behavior should be tested.

Computational fluid dynamics (CFD) simulations were used for the evaluation of critical issues associated with coating processes with the aim of developing and optimizing this important industrial technology. Four different models, namely, the constant viscosity, shear thinning, Oldroyd-B viscoelastic, and Giesekus models, were analyzed and compared in a short-dwell coater (SDC) using a bio-based coating material. The simulation results showed that the primary vortex formations predicted by the viscoelastic models were highly dependent on the flow Deborah number, resulting in uneven stress distribution over the coated surface. For the viscoelastic models, the dominance of elastic forces over viscous forces gave rise to significant normal stress difference, primarily along the surface of the substrate paper. The shear-thinning phenomena predicted by the Giesekus model, however, tended to relax the stress development in contrast to the Oldroyd-B model. The observations indicate that a reduced coating velocity or modification of the coating material with a reduced relaxation time constant can significantly enhance the uniformity and thickness of the coating over the coated surface under controlled conditions.

Shale swelling is vital causing instability issues with water-based drilling fluids (WBDF). It happens because shale has reactive minerals causing swelling with water. Previously used inhibitors protected clay surface, but nanopores remained open. Physical plugging of nanopores is essential to improve swelling inhibition. Objective of this research is to identify a better shale swelling inhibitor. 0.1–1.1 wt% of Multi Walled Carbon Nanotubes (MWCNTs) is used to improve inhibition in bentonite wafers. MWCNTs is characterized by FESEM, TGA, and FTIR. Swelling inhibition, rheological, and filtration properties are determined upto 150 °C. MWCNTs based WBDF is also characterized by XRD to study MWCNTs effect on d-spacing. Rheological model study is performed. FESEM determined 94.5% purity, TGA confirmed thermal stability up to 904 °C, and FTIR found carbon bonds. MWCNTs has induced 57% swelling inhibition in comparison with base fluid. Rheological and filtration properties are improved potentially, that is, Rheology has improved 57% and filtration 55%. Drilling fluid samples are found following shear thinning and Bingham Plastic model with 0.933–0.97 R 2 and lowest RMSE values upto 100 °C. In future, MWCNTs can be used with other nanoparticles, polymers, and ionic liquids for swelling inhibition.

Most of the commercially available magnetorheological (MR) fluids are only tested up to 1200 1/s shear rates but with no magnetic field. Data are rarely available at high shear rates with magnetic field applied. In most of the applications where MR fluids are used, such as MR rotary brakes or MR translational dampers, the shear rates can be in the order of thousands and in some applications, the shear rates could be in the order of ten thousands (1/s) and higher. At these high shear rates, most MR fluids will be shear thinning and Bingham model will be inappropriate to use. The focus of this study is on the mathematical modeling of a drum-type MR rotary brake using the Herschel-Bulkey model.

This research examines the influence of homogeneous and heterogeneous chemical reactions on the peristaltic flow via an inclined permeable channel. The current investigation emphasizes on modeling the flow of blood in narrow arteries by taking convective and wall properties into account. The Ree‐Eyring non‐Newtonian model is used to govern the fluid flow due to its significance in understanding the behavior of dilatant, pseudoplastic, and viscous liquids. The variation in variable viscosity and thermal conductivity is considered for analyzing the complex rheological behavior of blood. The similarity transformations are used in the process of nondimensionalization. The series solution procedure is adopted to solve the governing nonlinear differential equations. The expressions for velocity, temperature, concentration, and trapped bolus are obtained. The computational results are analyzed with the help of graphs for shear thickening, shear thinning, and Newtonian fluid models. One of the significant findings of the current model is that an introduction of variable liquid properties improves the temperature and velocity profiles for Newtonian and pseudoplastic fluid models. Compared with the other theoretical models developed, the rheological and flow properties of various biological fluids can be derived from the model used in the present investigation.

Intra-aneurysmal hemodynamics such as wall shear stress and complex flow structures have been implicated as one of the important factors on the growth and risk of rupture of an aneurysm. In this study, the sensitivity of intra-aneurysmal blood flow dynamics to the shear-thinning rheological model is investigated by using the idealized geometries of a basilar tip aneurysm with two representative anterior-posterior (AP) tilting angles (2° and 30°). By choice of different rheological models, time-averaged hemodynamic factors such as wall shear stress, oscillatory shear index and relative residence time exhibited only minor effects. However, highly unstable flow present in idealized aneurysm model with 2° AP tilting angle facilitated an evident change in the instantaneous local flow dynamics with a considerable increase in effective viscosity. Nevertheless, the distinct hemodynamic phenotype, which characterizes the gross intraaneurysmal flow pattern, was independent of the choice of rheological model. This result suggests that the shear thinning viscous effect is of secondary importance in the gross hemodynamics in a basilar tip aneurysm but is appreciably enhanced on the instantaneous hemodynamics with unstable complex flow structures.

Tank-treading dynamics of red blood cells in shear flow: On the membrane viscosity rheology

Rheological characterization of continuous fiber—reinforced viscous fluid

To explore the role of hemodynamic in the initiation and progression of stenosis in carotid artery bifurcation, a Computational Fluid Dynamics (CFD) technique is applied. The effect of four rheology models is investigated as well as various mechanical phenomena. In this study, a Finite Element Method (FEM) was applied to simulate the physiologic Circumferential Strain/Stress (CS) Meanwhile, to investigate the role of vessel wall flexibility, a Fluid-Structure Interaction (FSI) analysis was applied. It was concluded that velocity profiles and WSS show sensitivity to arterial wall stiffening while shear thinning models do not have a dominant effect on the flow field.

This paper deals with the coupled effect of temperature and fly ash (FA) addition on rheological behaviour of natural hydraulic lime (NHL5) based grouts, currently used in masonry consolidation. The use of a grout injection technique for masonry consolidation may lead to an increase of hydrostatic pressure and lead to structural damage. This means that the thixotropic effects become self-evident in grout design. It was shown that there is a relation between the structuration rate of each grout and the pressure that occurs inside masonry during its consolidation. According to the results, it seems also that there is a grout threshold temperature (Tlimit) that separates a domain where the grout build-up structure area is almost constant, from another where flocculation area starts to increase significantly. We believe that in the first region the thixotropic effects are almost isolated from the irreversible effects (due to hydration). For the NHL5 based grout Tlimit = 20 °C and for the grout with NHL5 + 15 % of FA Tlimit = 15 °C. Grouts' characterization based on maximum resisting time, structuration rate and on the analysis of the hydraulic lime grout behaviour tested at different shear rates was performed using a shear thinning model and assuming that the structure is shear- and time-dependent. The goal is to use this methodology during mix proportioning and design for masonry injection purpose. The tested grout compositions were optimized compositions obtained in previous research using the design of experiments method.