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Difference Between Newtonian and Non-Newtonian Fluid

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An Introduction to Newtonian and Non-Newtonian Fluid

A subfield of physics known as fluid dynamics studies how fluids behave in various situations. The contrast between Newtonian and non-Newtonian fluids is an intriguing element of fluid dynamics. In many practical applications, it is essential to comprehend their contrasts.

Think of ketchup as an example to help you understand the idea. Ketchup does not flow as easily when squeezed as water does. Ketchup often starts off slowly before accelerating quickly and changing its viscosity, instead of flowing out smoothly. This behaviour is a prime example of non-Newtonian fluid behaviour.

Newtonian fluids, in contrast, include common fluids like air and water. Regardless of the applied force or shear stress, they flow predictably and consistently. Scientists and engineers can better understand and control the behaviour of fluids in a variety of sectors, such as manufacturing, medicines, and food processing, by researching the distinctions between Newtonian and non-Newtonian fluids.

Newtonian Fluids:

Newtonian fluids, named after Sir Isaac Newton, exhibit a linear relationship between shear stress and shear rate. This means that the viscosity of a Newtonian fluid remains constant regardless of the applied shear stress or the rate at which the fluid is deforming. In other words, the flow behaviour of Newtonian fluids is predictable and consistent under varying shear conditions.

Fluids known as Newtonian fluids have a linear relationship between the shear stress and the shear rate. In other words, regardless of the applied stress or the pace of the fluid's deformation, the viscosity of Newtonian fluids is constant.

Non-Newtonian Fluids:

A family of fluids known as non-Newtonian fluids lack a linear correlation between shear stress and shear rate. Non-Newtonian fluids' viscosity, in contrast to Newtonian fluids, is not constant and is subject to large variations depending on the flow circumstances. These fluids could exhibit complicated viscosity behaviours such as shear-thinning, shear-thickening, or others.

A wide range of compounds with various flow characteristics are included in non-Newtonian fluids. Non-Newtonian fluids behave in a more complicated way than Newtonian fluids, which have a constant viscosity. These fluids' viscosities can change based on the shear force that is applied, the shear rate, the passage of time, or other elements.

Last updated date: 26th Sep 2023
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Difference Between Newtonian and Non Newtonian Fluid:

For a variety of scientific, technical, and commercial purposes, it is essential to understand the distinctions between Newtonian and non-Newtonian fluids. Differentiating between various fluid types facilitates the choice of appropriate models, the design of practical procedures, and the performance optimisation of fluid flow systems.

The table describes the difference between newtonian and non newtonian fluid:



Newtonian fluid

Non-Newtonian fluid

Viscosity Relationship

Constant viscosity, linear relationship between shear stress and shear rate.

Variable viscosity, non-linear relationship between shear stress and shear rate.

Flow Behavior

Consistent flow behaviour at various shear rates.

Diverse flow behaviors, can exhibit shear-thinning or shear-thickening.

Shear Stress and Shear Rate Relationship

Directly proportional relationship.

Non-linear relationship.

Modeling and Analysis

Simple modelling using fundamental equations.

Rheological measurements and empirical models are needed for complex modelling.


Water, air, gasoline.

Ketchup, toothpaste, paint.


Using braking systems, dragging objects across a surface, or rubbing your hands together all involve sliding friction.

Various applications, including wheel-based transportation, ball bearings, and the rolling movement of rolling objects, frequently include rolling friction.

Examples of Newtonian and Non-Newtonian Fluids:

The examples of Newtonian fluids are as follows:

1. Water: A well-known illustration of a Newtonian fluid is water. Under typical circumstances, it shows a constant viscosity, which means that regardless of the applied shear force or shear rate, its flow behaviour stays constant.

2. Air: Air is also a Newtonian fluid, similar to water. Even under a variety of shear situations, it exhibits predictable flow properties and a steady viscosity.

3. Gasoline: Another illustration of a Newtonian fluid is gasoline. Regardless of the shear force or shear rate, it flows freely and maintains a consistent viscosity.

The examples of Non-Newtonian fluids are as follows:

1. Ketchup: Ketchup is a non-Newtonian fluid that exhibits shear-thinning behaviour. When at rest, it is thick and has a high viscosity. However, when a shear stress is applied (such as when pouring or squeezing the bottle), its viscosity decreases, allowing it to flow more easily.

2. Toothpaste: Another typical illustration of a non-Newtonian fluid is toothpaste. When pressure is applied during toothbrushing, it behaves like a shear-thinning fluid, becoming less viscous and flowing more freely.

3. Polymer solutions: Polymer-containing solutions, such as those found in some industrial processes or cosmetics, frequently display non-Newtonian behaviour. Depending on the particular polymer and concentration, they may exhibit shear-thinning or shear-thickening capabilities.


Non-Newtonian fluids display varying viscosity under shear stress, whereas Newtonian fluids have a constant viscosity independent of shear force. Non-Newtonian fluids may exhibit Bingham plastic behaviour, shear-thinning, or both. Differentiating between various fluid types enables more accurate and efficient design and optimisation of processes and systems by allowing for better knowledge and study of their responses.

The ability to flow and the lack of resistance to permanent deformation are characteristics of fluids. There are two main categories of fluids: Newtonian fluids and non-Newtonian fluids. The fluids that follow Newton's law of constant viscosity are known as Newtonian fluids. These liquids have constant viscosities and no shear stress or rate of shear. Non-Newtonian fluids are ones whose viscosity is not constant and whose relationship to shear stress varies. The two Newtonian fluids mentioned above are air and water. Blood, paint, toothpaste, and starch solutions are a few examples of non-Newtonian fluids.

FAQs on Difference Between Newtonian and Non-Newtonian Fluid

1. What is the difference between Newtonian and non-Newtonian fluid reactions?

When two surfaces move across one another, sliding friction happens, increasing resistance and causing energy loss. On the other hand, rolling friction involves the rolling of an item, with less resistance and energy consumption since there is less surface contact.

2. What are some Newtonian and non newtonian fluid reactions examples?

As a Newtonian fluid reaction, the flow of water from a tap is smooth and displays constant viscosity independent of shear force. Ketchup, on the other hand, initially resists flow but begins to pour under shear stress, exhibiting shear-thinning behaviour. This is a non-Newtonian fluid process.

3. Can a Newtonian fluid exhibit non-Newtonian behaviour?

Newtonian fluids normally keep a constant viscosity, but under specific circumstances, they may behave differently. For instance, some compounds, such as polymers or additives, can change a Newtonian fluid's viscosity and cause it to behave differently in certain situations.