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Properties of Engineering Materials and Surfaces
Published in Q. Jane Wang, Dong Zhu, Interfacial Mechanics, 2019
However, a fundamental understanding has been commonly accepted that, when the shear strain rate is very low, the shear stress is still approximately proportional to the shear strain rate and the constant of proportionality is the viscosity. As the shear rate increases, the viscosity may gradually decrease demonstrating a shear thinning behavior. If the shear strain rate is further increased, the shear stress will gradually reach its asymptotic limit τL, called the “limiting shear stress”, as schematically illustrated in Figure 2.19. It is believed that when the shear strain rate goes beyond the limit, slippage occurs either within the lubricant film or at the interface between the lubricant and one of the bounding surfaces, so that the shear stress stops increasing. Note that the limiting shear stress is a property of lubricant and is supposed to be a function of pressure and temperature.
Viscosity of Slurry
Published in Ko Higashitani, Hisao Makino, Shuji Matsusaka, Powder Technology Handbook, 2019
The viscosity of slurry usually does not take constant value. In usual cases, viscosity decreases as increasing shear rate or the strength of fluid flow, which is referred as “shear thinning.” Recently, the behavior of viscosity increase above critical shear rate is one of the active research fields. In this section, the viscosity behavior of a wide variety of slurries is described, and a brief description of the measuring technique of slurry viscosity is also given.
Recent Advances in Pharmaceutical Applications of Natural Carbohydrate Polymer Gum Tragacanth
Published in Amit Kumar Nayak, Md Saquib Hasnain, Dilipkumar Pal, Natural Polymers for Pharmaceutical Applications, 2019
Madhusmita Dhupal, Mukesh Kumar Gupta, Dipti Ranjan Tripathy, Mohit Kumar, Dong Kee Yi, Sitansu Sekhar Nanda, Devasish Chowdhury
Rheology describes ‘flow behavior’ of liquid, soft solid or solid in response to applied stress/force, that can be described by plotting shear diagram of shear rate versus shear stress. S. Balaghi et al., investigated flow behavior of six GT species of Iran and the results show that all species of GT dispersions had rheology of shear-thinning nature (2010). In rheology, shear thinning means the non-Newtonian fluid behavior where the viscosity decreases with an increase in shear strain. GT possesses pseudoplastic behavior, making it thixotropic, which on withdrawal of strain reverses back to its original state. Rheological behavior of GT varies with a diversity of species as differences in its constituents. While 1% Bassorin solution at 25°C shows a comparatively higher viscosity gel-like texture, Tragacanthin solution behaves like complex coil polymers of concentrated solution. However, little deformation in rheological property has been observed between Bassorin and Tragacanthin. The viscosity of both the fractions will decrease by increasing the temperature, but the viscosity of the Bassorin is less sensitive to heat than Tragacanthin. Moreover, for similar concentrations, Bassorin solution has a higher viscosity than Tragacanthin and whole GT. This confirms GT fractions have differential rheological properties within the same species (Mohammadifar et al., 2006).
Influence of variable thermal conductivity and diffusion coefficients in the flow of Jeffrey fluid past a lubricated surface with homogeneous-heterogeneous reactions: A finite-difference approximations
Published in Numerical Heat Transfer, Part A: Applications, 2023
Muhammad Ramzan, Hina Gul, Hassan Ali S. Ghazwani, Kottakkaran Sooppy Nisar, Mohamed Abbas, Chandu Veetil Ahamed Saleel, Seifedine Kadry
The envisioned mathematical model is formed assuming the subsequent conditions:An incompressible MHD Jeffrey fluid flow is assumed near a stagnation point on an unbounded lubricated sheet orthogonally in the xy-plane with the liquid flow confined to y > 0. As depicted in Figure 1, the lubricated plate is positioned along the x-axis The Cartesian coordinate is used with the x-axis along the plate and the y-axis normal to the plate.Lubrication is accomplished by a power-law (shear-thinning) fluid.Variable thermal conductivity and diffusion coefficients in the existence of homogeneous-heterogeneous reactions are taken into account.It is understood that the surface temperature is Tw and T∞ is the ambient temperature with Tw>T∞.
Compressive stress relaxation behavior of articular cartilage and its effects on fluid pressure and solid displacement due to non-Newtonian flow
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2021
Figure 4 shows profile of fluid pressure p(x, t) as a function of distance x for linear permeability M = 0 at t = 0.1 for shear-thinning, Newtonian and shear-thickening during fast () and slow rate of compression () on left and right graphs, respectively. Fluid pressure decreases with an increase in power-law index n except for the shear-thickening fluid during the slow rate of compression. But pressure effects are more profound in the fast rate of compression as compared to the slow rate of compression. Fluid pressure increases linearly for both cases of shear-thinning fluid ), but for the fast rate of compression fluid pressure increases significantly. This is due to the fact that the viscosity of shear-thinning fluid decreases under shear stress. It is important to note that for all cases of power-law indexes behavior show at x = 0 is totally opposite of profile of fluid pressure at x = 1. Moreover, high fluid pressure causes more exudation of fluid, due to which fluid pressure for shear-thinning fluid drops significantly as compared to Newtonian and shear-thickening fluid and this result is consistent with previous studies of the interstitial flow field in the tissue (Wang et al. 2001).
A physical basis for non-Newtonian power-law viscosity
Published in Soft Materials, 2019
An experimental example on the viscosity of a solution of sodium carboxymethylcellulose (CMC) is presented. CMC finds widespread applications as a viscosity modifier in diverse applications ranging from food industries to rock drilling. A power-law has frequently been used to describe the viscosity of CMC solutions (3–6). However, at low shear rates, deviations from power-law behavior occur with viscosities tending toward a plateau (7,8). Shear thinning in this material is due to the shear-induced alignment of polymer molecules parallel to the direction of shear. At rest and at low shear rates, molecules will tend to form tangled masses and these straighten as shear rate is increased. The temperature dependence of the consistency index has generally been found to obey the Arrhenius relationship, Eq. (4) (9), and the rate exponent appears to increase linearly with temperature (5,10). The dimensionality of is thus further complicated by being temperature dependent.