What happens during shear thinning?

Shear thinning is a phenomenon characteristic of some non-Newtonian fluids in which the fluid viscosity decreases with increasing shear stress. Shear thickening is the opposite phenomenon.

What is an example of a shear thinning fluid?

Shear thinning fluids, also known as pseudo-plastics, are ubiquitous in industrial and biological processes. Common examples include ketchup, paints and blood. Non-Newtonian behavior of fluids can be caused by several factors, all of them related to structural reorganization of the fluid molecules due to flow.

What causes a non-Newtonian fluid?

Why do non-Newtonian fluids matter? 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.

What is molecular 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.

Is coffee a non-Newtonian fluid?

Because coffee is shear thinning, it classifies as a non-Newtonian fluid and possibly explains why we spill coffee much more easily when walking with a cup of it. The faster we walk and jostle the cup, the lower the viscosity.

Is honey a non-Newtonian liquid?

Honey is an example of a non-Newtonian fluid – a fluid that changes its behavior when under stress or strain.

How do you know if a liquid is Newtonian?

More precisely, a fluid is Newtonian only if the tensors that describe the viscous stress and the strain rate are related by a constant viscosity tensor that does not depend on the stress state and velocity of the flow.

What is the main characteristic of a non-Newtonian liquid?

A non-Newtonian fluid is a fluid that does not follow Newton’s law of viscosity, i.e., constant viscosity independent of stress. In non-Newtonian fluids, viscosity can change when under force to either more liquid or more solid. Ketchup, for example, becomes runnier when shaken and is thus a non-Newtonian fluid.

What are examples of non-Newtonian fluids?

NON-NEWTONIAN FLUIDS

• Dilatant – Viscosity of the fluid increases when shear is applied. For example: Quicksand. Cornflour and water. Silly putty.
• Pseudoplastic – Pseudoplastic is the opposite of dilatant; the more shear applied, the less viscous it becomes. For example: Ketchup.

How can I make non-Newtonian fluid at home?

Start with one part water in a bowl. Slowly add 1.5 to two parts cornflour, stirring constantly. Starch particles become suspended in water — but too much water will create liquid. “You need the tipping point, at the non-Newtonian threshold,” says Podolefsky.

What are examples of non Newtonian fluids?

Which is an example of Newtonian shear thinning?

n =1 corresponds to Newtonian behavior. Typically, for shear thinning fluids, n lies between 1/3 and 1/2 , even though other values are possible. Examples of shear-thinning fluids are polymer melts such as molten polystyrene, polymer solutions such as polyethylene oxide in water, and some paints.

How is shear stress related to shear thinning?

Classification of fluids with shear stress as a function of shear rate: Pseudoplastic, Bingham and Bingham pseudoplastic all show reduction in apparent viscosity with increasing shear rate. In rheology, shear thinning is the non-Newtonian behavior of fluids whose viscosity decreases under shear strain.

How are non Newtonian fluids dependent on shear rate?

Non-Newtonian fluids may be dependent on shear rate (force) or time. Pseudoplastic (shear-thinning) – As force is applied, the liquid viscosity thins. Think of juice concentrates, purees, and emulsions. Dilitant (shear thickening) – As force is applied, the liquid viscosity thickens. Think of liquid chocolate.

Which is the best non Newtonian shear rate model?

The Bird-Carreau model is mostly used for food, beverages and also blood flow applications. 3. Cross-Power Law Model The Cross-Power law model is also a four parameter model that covers the entire shear rate range.