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Fundamental Concepts
Published in William S. Janna, Introduction to Fluid Mechanics, Sixth Edition, 2020
Examples of Newtonian fluids are water, oil, and air. If a fluid cannot be described by Equation 1.10, it is called a non-Newtonian fluid. On the basis of their behavior, these fluids are divided into three categories: time-independent, time-dependent, and viscoelastic.
Ocean Hydrodynamics
Published in Victor Raizer, Optical Remote Sensing of Ocean Hydrodynamics, 2019
In our text, we consider a Newtonian fluid only, which is continuous, homogeneous, and macroscopic medium. The viscosity of the Newtonian fluid remains constant at constant temperature, pressure, and time (for a non-Newtonian fluid the viscosity varies with time; this fluid represents various plastic and polymer liquid materials).
Introduction to Convection
Published in William S. Janna, Engineering Heat Transfer, 2018
From our experience with fluids, we know that, if we invert a glass of water, the flow pattern is vastly different from that of an inverted jar of mayonnaise. The mayonnaise behaves quite differently under the action of an applied shear stress than does water, and the mayonnaise cannot be accurately described by Equation 5.1. Therefore, mayonnaise is an example of what is known as a non-Newtonian fluid. Other examples include paint, printer’s ink, chocolate mixtures, and flour dough. Examples of Newtonian fluids are water, oil, air, and glycerine. The absolute or dynamic viscosity of various substances can be obtained from data in the Appendix tables (C for liquids and D for gases). In this text, we will work exclusively with Newtonian fluids.
Wall jet nanofluid flow with thermal energy and radiation in the presence of power-law
Published in Numerical Heat Transfer, Part A: Applications, 2023
Waqar Khan Usafzai, Abdulkafi. M. Saeed, Emad H. Aly, V. Puneeth, I. Pop
Power-law nanofluids moving through various mediums have drawn significant research in a wide range of industries during the past decades. Newtonian fluids are those that follow Newton’s law of viscosity and show a direct proportion between shear stress and strain rate in laminar flow. Whereas, non-Newtonian fluids do not obey Newtonian viscosity law. Some colloids, milk, gelatin, blood, and heavy oil are examples of common nonlinear power-law fluids. The plug-like aspect of the velocity profile increases with decreasing power-law index, resulting in a blunt or plug-like flow for the power-law fluid. Numerous authors studied natural convection in power-law nanofluids. Ellahi et al. [15] studied the heat transfer properties, including the amount of heat conducted by the power-law nanofluid. Khan et al. [16] dealt with the Blasius flow model for power-law nanofluid flowing over a stretching sheet that is being convectively heated. Wang et al. [17] performed theoretical analysis to understand the heat transfer properties of power-law nanofluid in rectangular cavities. The significant findings of Ojeda and Mendez [18] showed rapid decrement in the Nusselt number for shear-thinning base fluids, whereas it increases asymptotically for shear-thickening fluid. Selimefendigil and Öztop [19] investigated the thermal performance of a coupled conjugate thermo-fluid system with various cooling configurations. Alkhatani et al. [20] considered the geometry of a vertical stretching sheet to analyze the flow of power-law nanofluid. For further details, the reader is advised to see the references [21–25].
Research on rheology performance and sealing effect of alkali-activated GGBS paste used for tunnel leakage plugging
Published in Journal of Sustainable Cement-Based Materials, 2023
Ping Li, Shiwei Liu, Yin Bai, Jianhui Tang, Jun Tao
Viscosity is a basic rheological parameter of fluids and reflects the resistance of a fluid to deformation at a given rate. A fluid can be classified as Newtonian fluid if the viscosity is constant and independent of shear rate. On the other hand, the viscosity of a non-Newtonian fluid changes with shear rate. Figure 5 shows the variation in viscosity of AAS paste with shear rate at an activator concentration of 3 mol/L and a temperature of 20 °C. It can be seen that there was a continuous reduction in measured viscosity with increasing shear rate at a reducing rate irrespective of the time interval. Therefore, the AAS paste prepared in this study was classified as non-Newtonian fluid. Note that the viscosity of AAS paste measured at different time intervals differed a lot at a given shear rate. For example, when the shear rate was 20 s−1, the viscosity was 6.75 Pa·s after 1 min. The viscosity reduced to 3.42 Pa·s and 3.04 pa·s at the 41 and 81 min, respectively. However, the viscosity increased by 74% when the time interval further increased from 81 min to 121 min. The reversal in measured viscosity can be explained by the fact that the generated hydration products of AAS paste overtook the structural rupture caused by rotor motion, resulting in enhanced deformation resistance. Similar relationships between viscosity and shear rate were obtained at different activator concentrations (i.e. 1 and 2 mol/L) and temperatures (i.e. 10 and 30 °C).
Effect of surfactants on the deformation of single droplet in shear flow studied by dissipative particle dynamics
Published in Molecular Physics, 2018
Yuzhou Zhang, Junbo Xu, Xianfeng He
Based on Irving–Kirkwood method [41], the viscosity can be calculated with the following equation: where V is the system volume and N is the number of beads. uiz = viz and are peculiar velocity components of bead i in the z-direction and in the x-direction, respectively, with being the stream velocity at position z. fijx is the x-component of the force exerted on bead i by bead j. The size of the simulation box was 80 × 80 × 80, and Lees–Edwards condition (LEC) [42] was applied to generate the shear flow in x-direction. As the viscosity ratio of the droplet to the continuum phase is fixed at 1 in this article, we calculated the viscosity with system of single component, and the beads were randomly distributed initially. The time step size was set to 0.02. First, 10,000 time steps of simulation were performed without LEC, and then LEC method with different values of shear rate was applied. After 200,000 time steps, the flow field reached the steady state and then 10,000 more time steps of simulation were performed to calculate the viscosity. For Newtonian fluid, the shear viscosity should not change with the shear rate. In our simulation, when the friction factor γ is fixed at 4.5, the shear viscosity calculated from flows at different shear rate , 0.01, 0.02, 0.03 and 0.05 is ηzx = 0.958 ± 0.003, with a relative deviation less than 0.5%.