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Properties and Characteristics of Water and Wastewater
Published in Donald R. Rowe, Isam Mohammed Abdel-Magid, Handbook of Wastewater Reclamation and Reuse, 2020
Donald R. Rowe, Isam Mohammed Abdel-Magid
Time-independent fluids — This type of fluid behavior may be subdivided into several groups: Pseudoplastic (shear thinning): are those which become increasingly less viscous as the rate of shear is increased.Dilatant (shear-thickening): dilatance is the opposite of pseudoplasticity. This phenomenon is not common and is associated with suspensions of repelling particles.Viscoplastic or Bingham plastics: in this case a finite yield stress is required to initiate flow when the solid phase of a suspension is present in sufficient concentration to form a continuous but disoriented structure.
Fundamental Concepts
Published in William S. Janna, Introduction to Fluid Mechanics, Sixth Edition, 2020
Wet beach sand and other water solutions containing a high concentration of powder are examples of dilatant fluids (Figure 1.4). These fluids exhibit an increase in viscosity with increasing shear stress. A power law equation (called the Ostwald-deWaele equation) usually gives an adequate description: τ=KdVdynn>1
Flow of Fluids in Food Processing
Published in Susanta Kumar Das, Madhusweta Das, Fundamentals and Operations in Food Process Engineering, 2019
Susanta Kumar Das, Madhusweta Das
Pseudoplastic liquids show a decrease in shear stress with an increase in shear rate (slope or viscosity decreases). Many foods such as gelatinized starch suspension, emulsion (mayonnaise) puree, pulp, ice cream mix, egg white, chocolate melt, and protein concentrates are examples of shear-thinning liquids (Rao, 2005). In shear-thinning liquids, particles in suspension align themselves, or dispersed phase in emulsion possesses a tendency to aggregate. These phenomena allow the path of least resistance in flow (Toledo, 2007). Dilatant liquids show an increase in shear stress with an increase in shear rate (slope or viscosity increases). In dilatant liquids, dispersed phase in emulsion swells or changes shape or long molecules undergo cross-linking each other (Toledo, 2007). Shear-thickening liquids are not very common in food systems. Honey and cooked starch suspensions are few examples of shear-thickening liquids (Rao, 2005).
Hydraulic transportation of coal combustion products for mine fill
Published in Particulate Science and Technology, 2019
The fluids which do not follow this type of linear relationship are known as non-Newtonian fluids. The downward curve represents shear thickening or dilatants behavior and the upward curve represents shear thinning or pseudo-plastic behavior. The dilatant fluids are characterized by growing viscosity and shear stress while expanding the shear rate (Lemmer, Hartmann, and Wolf 1999), whereas pseudo-plastic fluids show a reduced alteration of shear stress when increasing the shear rate. The fluids are known as Bingham plastic fluid when they do not show any flow until a threshold shear stress. The pseudo-plastic behavior of a fluid is well expressed by the following equation:where τ = shear stress (Pa), K =flow consistency index (Pa · s), γ = shear rate (s−1), and n =flow behavior index.
A practical method for predicting the friction factor of power-law fluids in a rectangular duct
Published in Chemical Engineering Communications, 2019
Mehmet Ayas, Jan Skocilas, Tomas Jirout
where K is fluid consistency and n is the flow behavior index. For power-law fluids with n values greater than one (n > 1), their apparent viscosity increases with increasing shear rate. These are known as shear thickening (dilatant) fluids. Beside the n values are less than one (0 < n < 1), their apparent viscosity decreases with increasing shear rate. These are known as shear thinning (pseudoplastic) fluids (Chhabra and Richardson, 1999). The case of n = 1 corresponds to a Newtonian fluid. It should be noted that most non-Newtonian fluids exhibit pseudoplastic flow behavior, and only a small number of representatives of dilatant fluids can be found in nature.
Capturing the onset of thermocapillary convection in the Cattaneo–Christov flow of electrically conducting thin film of Welan gum solution
Published in Waves in Random and Complex Media, 2022
When n = 1 the fluid shows Newtonian behavior whereas the fluid behaves as a shear-thickening one when n>1, and when n<1 the fluid behaves like pseudo-plastic or is a shear-thinning fluid. Dilatant fluids have a viscosity function which increases with the shear rate. The fluid becomes thicker and more viscous with increasing shear rates. Whereas in the case of pseudo-plastic fluid, viscosity function varies inversely with increasing shear rates. These fluids become thinner and less viscous with increasing shear rates.