What is the difference between shear thinning and shear thickening?
What is the difference between shear thinning and shear thickening?
A fluid is shear thickening if the viscosity of the fluid increases as the shear rate increases (see Figure 2). Fluids are shear thinning if the viscosity decreases as the shear rate increases.
What are shear thinning and shear thickening fluids?
Some liquids behave differently when stress is applied (application of force). Shear thickening liquids increase in viscosity as stress increases. Shear thinning liquids decrease in viscosity as stress increases.
How do you quantify shear thinning?
Shear thinning index can be calculated by dividing apparent viscosity at the lowest speed by the value of apparent viscosity at the highest speed (typically at 2 and 20 or 5 and 50 rpm). The resultant ratio is an index of shear thinning.
What is meant by shear thinning?
In rheology, shear thinning is the non-Newtonian behavior of fluids whose viscosity decreases under shear strain. It is sometimes considered synonymous for pseudoplastic behaviour, and is usually defined as excluding time-dependent effects, such as thixotropy.
Why does shear thickening occur?
Shear thickening behavior occurs when a colloidal suspension transitions from a stable state to a state of flocculation. A large portion of the properties of these systems are due to the surface chemistry of particles in dispersion, known as colloids.
What is shear thickening example?
Corn starch and water (oobleck) Cornstarch is a common thickening agent used in cooking. It is also a very good example of a shear-thickening system. When a force is applied to a 1:1.25 mixture of water and cornstarch, the mixture acts as a solid and resists the force.
Is honey a shear thinning fluid?
In a non-Newtonian fluid, the viscosity changes in response to an applied strain or shearing force, thereby straddling the boundary between liquid and solid behavior. Blood, ketchup, yogurt, gravy, mud, pudding, custard, thickened pie fillings and, yes, honey, are all examples of non-Newtonian fluids.
What is shear thickening system?
Introduction. Shear thickening fluids (STFs) are colloidal dispersions which exhibit an abrupt increase in viscosity with increasing of shear rate or applied stress [1]. The concentrated colloidal suspensions demonstrate a shear thickening behavior, which promotes a discontinuous viscosity above a critical shear rate.
What’s the difference between shear thickening and shear thinning?
Shear thinning. Shear thickening is the opposite phenomenon. (By contrast to both, viscosity in Newtonian fluids is by definition independent of the forces exerted on the fluid.) Fluids that exhibit shear thinning are sometimes called pseudoplastics and are typically complex fluids such as blood, motor oil, ketchup, and even whipped cream,…
Which is an example of a shear thinning fluid?
Shear-thinning fluids or pseudo-plastic fluids exhibit a proportional increase in shear rate as a function of shear stress ( Koleske, 2012; Mezger, 2014; Wilczyński, 2001 ). Shear-thinning fluids are encountered relatively frequently; for example, ink and varnishes exhibit shear-thinning flow behavior.
When does shear stress cause viscosity to decrease?
Shear thinning. Shear thinning is a phenomenon characteristic of some non-Newtonian fluids in which the fluid viscosity decreases with increasing shear stress.
How are pseudoplastic solutions related to shear thinning?
These are considered pseudoplastic. They flow instantaneously upon application of stress but also display shear thinning behavior. Polymer solutions exhibit pseudoplastic flow as does bread dough and many paints and cosmetics. A plot of viscosity versus shear rate for different types of materials is shown in Figure 2.