# Non Newtonian Fluid

Delve into the fascinating universe of Non Newtonian Fluid, a vital concept in the field of engineering. This comprehensive resource aims to elucidate the complex characteristics of this unusual fluid that defies Newton's Law of Viscosity, by exploring its meaning, history, and distinguishing factors from its Newtonian counterpart. Discover widespread examples of Non Newtonian Fluids in engineering, their critical role in various industries, and promising avenues opened up by contemporary research. Learn, too, about the intriguing dynamics of Non Newtonian Fluid and how they're utilized in practical applications. This article pushes the boundaries of knowledge, advancing your understanding of how Non Newtonian Fluid revolutionises the world of engineering and beyond.

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## Understanding Non Newtonian Fluid

A Non Newtonian Fluid is a fascinating subject in the field of engineering, particularly in fluid mechanics. The behaviour of these fluids is contrasting to what you may typically anticipate from common liquids. But what makes these fluids so exotic?

### Non Newtonian Fluid Meaning: A Basic Introduction

Non Newtonian Fluids deviate from the simple, conventional model of fluids. When you think about a fluid, you'd typically envisage something like water - a substance whose rate of flow remains steady regardless of the force on it. This belief is founded on Sir Isaac Newton's law of viscosity, which postulates that the rate of fluid flow is proportional to the applied force. However, Non Newtonian Fluids defy this law.

The term 'Non Newtonian Fluid' is used to describe fluids that do not follow Newton's law of viscosity. The shear stress (force per unit area) is not linearly related to the shear rate (rate of change of velocity perpendicular to the surface) in these fluids and it can depend on factors like the duration and history of the applied stress.

They feature prominently in a variety of engineering and scientific applications, such as in food processing, cosmetics, and biomedical engineering. Understanding how to work with these fluids can offer remarkable opportunities for innovation.

#### History and Concept of Non Newtonian Fluid

The concept of Non Newtonian Fluids traces its history back to the 19th century. During this period, physicists began to recognize that numerous substances, particularly biologically related materials, didn't quite behave according to Newton's law of viscosity. Despite several attempts, it took scientists until the early 20th century to fully comprehend the peculiar behaviour of these fluids.

A canonical example of a Non Newtonian Fluid is a mixture of cornstarch and water, often called "Oobleck." When you stir it slowly, it behaves like a liquid. If, however, you hit it suddenly or stir it rapidly, it acts like a solid because of the temporary formation of a network of cornstarch particles. This behaviour, where a fluid's viscosity increases with the shear rate, is an example of shear thickening.

#### Difference between Newtonian and Non Newtonian Fluid

Newtonian and Non Newtonian Fluids are principally differentiated by how they react to shear stress. Newton believed that the flow behaviour of a liquid, or its viscosity, remained constant, irrespective of the forces acting upon it.

Newtonian Fluids obey Newton's law of viscosity, where the shear stress is directly proportional to the shear rate. Examples include simple liquids like water and oil.

Non Newtonian Fluids, on the other hand, operate quite differently. As stated before, their shear stress is not directly proportional to the shear rate. According to the viscosity change, these fluids can be classified as pseudoplastic, dilatant, thixotropic, rheopectic, viscoelastic.

 Fluid Type Viscosity Behaviour Pseudoplastic Viscosity decreases with increasing shear rate Dilatant Viscosity increases with increasing shear rate Thixotropic Viscosity decreases with time at a constant shear rate Rheopectic Viscosity increases with time at a constant shear rate Viscoelastic Displays elastic properties during deformation

Recognizing and comprehending these differences is essential to manage and navigate the exciting world of fluid mechanics.

## Examples of Non Newtonian Fluids in Engineering

In engineering, Non Newtonian Fluids such as foam, emulsions, and suspensions often come into play. They're used in a myriad of ways, from drilling mud in petroleum engineering to concrete in civil engineering. Understanding the character of these fluids enables engineers to manipulate and employ them to tackle complex real-world technical problems.

### Interesting Non Newtonian Fluid Examples in Everyday Life

You encounter Non Newtonian Fluids more often than you might realise in your daily life. They're not just confined to the lab; they're in your kitchen, your bathroom, and even on your plate! Here are some fascinating everyday examples:

• Custard: Who would have thought that the luscious and creamy dessert you relish after a hearty meal is a Non Newtonian Fluid? Indeed, custard powder mixed with water creates what is sometimes referred to as 'custard soup', a unique Non Newtonian Fluid. Its diluted slimy and creamy texture exemplify the important characteristic of Non Newtonian Fluids where viscosity changes with the application of stress.
• Toothpaste: The smooth, semi-solid substance you squeeze out from your toothpaste tube every morning and night is a perfect example of a Non Newtonian Fluid. Its capacity to maintain its shape on the toothbrush and liquify during brushing can be attributed to its viscoelastic properties.
• Ketchup: This everyday condiment is thixotropic, meaning its viscosity decreases over time when a force is applied. Have you ever struck the bottom of a ketchup bottle to get the sauce flowing? That’s you experiencing the Non Newtonian nature of ketchup!

Looking beyond your kitchen and delving deeper into the mechanical aspect, Non Newtonian fluids also find applications in car clutch systems, bullet-proof vests, and even in constructing earthquake-resistant buildings.

#### Discovery of Non Newtonian Fluids in Nature

Nature has been astoundingly clever to inherently use the unique characteristics of Non Newtonian Fluids not just around us, but also within us! Your blood is perhaps the most amazing and critical Non Newtonian Fluid that courses through your veins. Because of its shear-thinning nature, blood can flow more quickly when subjected to greater forces. In simpler terms, under normal conditions, blood exhibits higher viscosity, but when your heart beats, the increased force decreases its viscosity, facilitating efficient flow.

Interestingly, the lava that oozes out of a volcano is also a Non Newtonian Fluid. Lava flows slowly when untouched, exhibiting great viscosity. However, under the influence of gravity or the dispersing force of a volcanic explosion, lava's viscosity decreases, enabling it to flow freely and quickly.

Moving onto the underwater world, quicksand, a mixture of sand and water can behave differently under different stress conditions. When undisturbed, quicksand seems like a solid land. But the moment you step on it, the stress triggers its liquid behaviour, making it act like a Non Newtonian Fluid!

#### Common Non Newtonian Fluids Used in Science Experiments

Non Newtonian Fluids provide a fun way of understanding and exploring the complexities of fluid dynamics. There's nothing quite like hands-on experience to truly appreciate how these substances behave differently at different stress levels.

The most common fluid used in science experiments is a mixture of cornstarch and water, fondly called 'Oobleck'. This strange concoction is easy to make and incredibly fun to play with. When subjected to a quick jab or stir, it solidifies, but upon releasing the stress, it flows like a liquid.

Another common Non Newtonian Fluid found in labs is silly putty. This playful substance is actually a silicone polymer and exhibits both viscous and elastic characteristics, making it incredibly flexible and stretchy. It also introduces children to Non Newtonian Fluids and their interesting behaviours, making learning an enjoyable process!

Believe it or not, your homemade slime, which is just a mixture of glue, water, and borax, is also an excellent Non Newtonian Fluid. In fact, it is this bizarre behavioor that makes slime so much fun to play with and learn from.

## Delving into Non Newtonian Fluid Dynamics

Unravelling the underlying principles and deriving deep insights into the dynamics of Non Newtonian Fluids can be intellectually stimulating. From biomechanics to geophysics, the behaviour of these often perplexing fluids holds the key to many scientific phenomena. So, what's the theory that elucidates Non Newtonian Fluid Dynamics? How do you capture the essence of these fluids in motion?

### The Theoretical Framework behind Non Newtonian Fluid Dynamics

While an analysis of Newtonian fluids typically utilises Newton's law of viscosity giving a linear relationship between shear stress and rate of deformation, Non Newtonian fluids require a different theoretical approach. In essence, the flow behaviour of non-Newtonian fluids cannot be described using a single constant value of viscosity. Instead, the apparent viscosity, or the resistance to flow, varies depending on the applied stress or deformation. This complex relationship is often described by the Ostwald-de Waele power law model.

The Ostwald-de Waele model characterises the shear stress $$\tau$$ to the shear rate $$\dot{\gamma}$$ relation for Non Newtonian Fluids through a power law given by $$\tau = K (\dot{\gamma})^n$$, where $$K$$ is the fluid consistency index, a measure of the fluid's resistance to deformation, and $$n$$ is the fluid behaviour index, a measure of the degree of non-Newtonian behaviour of the fluid. If $$n = 1$$, the fluid behaves as a Newtonian fluid. If $$n \< 1$$, the fluid is shear-thinning or pseudoplastic, and if $$n > 1$$, the fluid is shear-thickening or dilatant.

An interesting manifestation of non-Newtonian behaviour that scientists have been intrigued by is the phenomenon of "shear banding" where the fluid's flow is segregated into layers of different velocities. Predicting flow behaviour in such scenarios is challenging and requires intricate mathematical models that incorporate not just shear rate and stress but also factors like temperature and time.

#### Understanding the Non Newtonian Fluid Behaviour

To gain a comprehensive understanding of Non Newtonian Fluids, it's essential to delve deeply into the different types of behaviour these fluids can exhibit. As mentioned earlier, they can be categorized broadly into shear thinning, shear thickening, thixotropic, rheopectic and viscoelastic fluids.

Shear-thinning fluids, also known as pseudoplastic fluids, like ketchup or blood, become less viscous as the shear rate increases. This feature is beneficial in products that need to be thick when still but thin when moving, such as paints that need to stay on a brush but spread smoothly when applied to a wall.

On the flip side, shear-thickening fluids, also known as dilatant fluids, like cornstarch in water, behave in the opposite manner; they increase in viscosity as the shear rate increases. This property has interesting applications in technology such as body armour where the fluid can provide flexibility at rest but solidify upon impact to provide protection.

Thixotropic fluids exhibit a time-dependent decrease in viscosity under constant shear. An example of a thixotropic fluid is paint, which remains fluid while being brushed on, but soon 'sets' and becomes more viscous.

Rheopectic fluids present a time-dependent increase in viscosity under constant shear. This behaviour is less common but can be seen in some lubricants.

Viscoelastic fluids, like melted cheese or marshmallows, exhibit behaviour that is both viscous and elastic. These types of materials can be deformed easily, but also spring back to their original shape.

Understanding these different behaviours is crucial not merely to comprehend these Non Newtonian Fluids, but also to utilize their unique properties to devise innovative problem-solving techniques in different fields of engineering.

#### Demonstration of Non Newtonian Fluid in Motion

One of the most exciting ways to grasp the unique behaviour of Non Newtonian Fluids is to see them in action! Many experiment-based demonstrations capture these fluids under varying conditions of stress and strain, manifesting their intriguing characteristics.

Perhaps the most iconic demonstration of a Non Newtonian Fluid is the "walk on water" experiment with Oobleck. When a person tries to walk slowly on a pool filled with Oobleck, they'll sink due to its liquid-like behaviour. But, if a person runs or hops quickly on it, they can essentially walk on the fluid without sinking! This is because the quick application of force thickens the fluid, transforming it into a solid-like state that resists further deformation.

Another practical demonstration that brings out Non Newtonian behaviour is a speaker experiment with a cornstarch-water mixture. When placed on a speaker emitting sound at a certain frequency, the mixture starts exhibiting lively undulations, appearing almost to 'dance' with the rhythm. The vibrations evidently induce a rapid variation in shear rates, causing the fluid to switch continuously between its liquid and solid states, producing the fascinating display.

These demonstrations make the abstract concept of Non Newtonian Fluids tangible and encourage a deeper understanding of this diverse class of materials.

## Applications of Non Newtonian Fluid in Engineering

The diverse and seemingly anomalous behaviours of Non Newtonian Fluids can be cleverly exploited in various engineering applications. From materials science to chemical and industrial processes, these unique fluids simply transform the way problems are approached and solutions are conceived.

### Innovative Non Newtonian Fluid Applications in Industry

In the annals of industrial production, specifically in process engineering, the behaviour of Non Newtonian Fluids has been studied as an important facet of fluid flow and heat transfer analyses. Given the fact that many industrial fluids do not adhere to Newton's law of viscosity, understanding non-Newtonian behaviour becomes crucial for optimising various processes. One notable instance lies in the manufacturing of polymer solutions or suspensions that often exhibit non-Newtonian characteristics. Applying the right amount of shear force ensures that these fluids maintain the quality of their characteristics.

Similarly, in the food industry, the role of non-Newtonian fluids is quite prominent. Many food items – like sauces, dairy products and confectionery – exhibit non-Newtonian nature. Their rheological properties are vital for determining the taste, texture, stability, and palatability of the food product. Furthermore, these properties also play a major role in determining food processing parameters like pumping, mixing, and heat transfer.

Non Newtonian Fluids have also introduced a radical shift in the pharmaceutical industry. Various formulations like gels, creams, ointments exhibit non-Newtonian behaviour. Effective management of their rheological traits ensures better efficacy of the drug.

Another important application in industry is in the manufacture of body armours. Certain Non Newtonian Fluids, called sheer-thickening fluids, become hard upon impact and hence have been used to create bullet-resistant materials.

#### Use of Non Newtonian Fluid in Materials Science

The interesting attributes of Non Newtonian Fluids also pervade the vast world of materials science. Non Newtonian Fluids have been found to possess a unique potential in crafting smart materials. Key to this application is the understanding and manipulation of their flow characteristics under different conditions.

An intriguing implementation of non-Newtonian behaviour rests within the creation of smart fluids. These fluids, including electrorheological and magnetorheological fluids, respond to external fields by changing their viscosity. Aligned with the spirit of materials science, this adaptability can be utilised to tailor-make materials that meet specific industrial requirements.

Non Newtonian Fluids have also sparked insights into the development of self-healing materials. These materials, typically fluid-filled capsules embedded into a matrix, rupture upon the event of a crack to release a healing agent. As the healing agent interacts with the catalysing particles in the matrix, it forms a polymer that seals the crack.

Another significant application of Non Newtonian Fluids seen in materials science is in the area of 3D printing. The viscous properties of non-Newtonian fluids are leveraged for creating precise and robust designs.

#### Beneficial Properties of Non Newtonian Fluid Exploited Across Sectors

The multifaceted characteristics of Non Newtonian Fluids serve as a treasure chest of possibilities, not just within engineering but in numerous sectors. From practical and industrial applications to advancing scientific theory, let's examine the key properties that stand out.

• Adaptability: Non Newtonian Fluids are shear-sensitive, which means their viscosity changes in response to a change in applied force. This property has been actively exploited to develop smart materials as discussed earlier.
• Flow controllability: Because the viscosity of Non Newtonian Fluids can be controlled by applying different amounts of force, it facilitates handling in various industrial processing operations such as pumping and heat transfer.
• Impact resistance: Certain Non Newtonian Fluids, specifically shear-thickening fluids, become rigid when subjected to high impact forces, thereby providing resistance to sudden impacts. This concept has been utilised in the design of modern protective gear and body armour.

All these properties, alongside many others, pave the way for the unique applications of Non Newtonian Fluids across sectors –manufacturing, technology, defence, and beyond. Every study centred around Non Newtonian Fluids unfurls a myriad of possibilities, reaffirming the fluid's status as a veritable cradle of innovative engineering solutions.

## Future Directions in Non Newtonian Fluid Research

Scouring the horizon of scientific enterprise, it is no surprise that the research focused on Non Newtonian Fluids is gaining momentum. The dynamic nature of these fluids and the plethora of their applications have made them a hotbed for intriguing and impactful research.

### Emerging Trends in the Study of Non Newtonian Fluids

With an ever-increasing interest in complex fluids, fresh perspectives and innovative methodologies are being charted out in the realm of Non Newtonian Fluids. Unfolding this narrative yearns probing into the recent breakthroughs and delineating the transformative ideas reshaping this field of study.

 Trend Description Digital Rheology Inspired by the recent advancements in digitisation and machine learning, this technique seeks to predict material properties from microstructure. Nano-rheology An emergent field aiming to measure rheological properties at nanoscale. Soft Matter Physics Continuing to widen its scope to examine the behaviour of such Non Newtonian Fluids as foams, gels and colloidal dispersions. Active Matter A domain that explores substances composed of self-driven agents, this field is progressively extending its focus to certain Non Newtonian Fluids.

As these research trends burgeon, they will undoubtedly deepen our comprehension of the intricate behaviours exhibited by Non Newtonian Fluids and aid in unlocking their latent potential.

#### Impact of Recent Research on Understanding Non Newtonian Fluid

The development in the research related to Non Newtonian Fluids has been instrumental in guiding the focus towards real-world applications of these unique fluids.

To begin with, the use of cutting-edge computing and numerical techniques has allowed for more accurate simulations of Non Newtonian Fluid flow, thereby aiding in a host of areas - from designing pharmaceutical manufacturing processes to enhancing materials science applications.

For instance, the accuracy of these simulations has enabled the creation of tunable rheological materials - materials that can have their viscosity controlled. This has significant applications in creating customizable 3D printed objects , where precise control over the flow characteristics of the printing material is crucial.

Equally impactful is the sweep of research in the field of smart and self-healing materials. This has paved the way for the development of materials that are capable of self-repairing damage, thereby increasing their potential for use in constructions, vehicles, and numerous other applications. The genesis of this innovation lies in the unique viscosity properties of Non Newtonian Fluids, a testament to the transformative power of focused research.

#### Prospects of Non Newtonian Fluid in Engineering and Beyond

The inspiring journey of Non Newtonian Fluids from complex fluids to transformative solutions underscores the potential these fluids bear for the future.

The ever-increasing understanding of these fluids has potentiated the proposition of their utilisation in several unexplored areas. A case in point is the domain of energy systems. Non Newtonian Fluids hold the capacity to improve the efficiency of biofuel production by acting as a suspension medium. Emerging studies are also keen on exploiting the exceptional properties of these fluids in the progression of fluid energy storage technologies.

Another avenue of significant potential is biomedical therapeutics. Numerous drug delivery systems and biomedical devices propose incorporating Non Newtonian Fluids to heighten efficiency. For instance, the theory of using magnetorheological fluids for minimally invasive targeted drug delivery systems is being actively researched.

Addressing sustainability concerns is also among the compelling prospects presented by Non Newtonian Fluids. With a surging interest in devising innovative solutions to environmental challenges, studies are being steered towards harnessing Non Newtonian behaviour to liven up waste treatment procedures. The erratic yet exciting journey of Non Newtonian Fluids has only begun unveiling its potential, making it a vibrant field, both from a research and application perspective.

## Non Newtonian Fluid - Key takeaways

• Non Newtonian Fluid: A fluid whose viscosity changes when stress/force is applied, demonstrated in examples such as custard, toothpaste and ketchup.
• Examples of Non Newtonian Fluids in nature: Blood, which changes viscosity under different forces for efficient flow and lava, which flows slowly until its viscosity decreases under disruptive forces.
• Common Non Newtonian Fluids used in science experiments: A mixture of cornstarch and water known as 'Oobleck', silly putty, and homemade slime.
• Non Newtonian Fluid Dynamics: The behaviour and properties of these fluids can be described by the Ostwald-de Waele power law model and are subject to phenomena such as "shear banding".
• Applications of Non Newtonian Fluid: Used in various fields such as industrial production, food industry, manufacturing of body armours and 3D Printing due to their unique properties like adaptability, flow controllability and impact resistance.

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What is a non-Newtonian fluid? Write in UK English.
A non-Newtonian fluid is a type of fluid in which the viscosity or flow behaviour changes when subjected to a force. Unlike Newtonian fluids, these do not maintain a constant viscosity and can either become thinner or thicker under stress.
What is an example of a non-Newtonian fluid? Write in UK English.
An example of a non-Newtonian fluid is cornflour mixed with water, often referred to as "oobleck". Other examples include ketchup, custard, honey, toothpaste, and blood.
How can I make a non-Newtonian fluid? Please write in UK English.
Non-Newtonian fluid can be made easily using cornstarch and water. Mix two parts cornstarch and one part water in a bowl. Stir well until you achieve a smooth, consistent mixture. The resulting substance is a non-Newtonian fluid.
Are non-Newtonian fluids liquids or solids?
Non-Newtonian fluids aren't categorised strictly as liquids or solids. They are a type of fluid whose flow properties change when subjected to different forces, displaying characteristics of both liquids and solids.
What are non-Newtonian fluids used for?
Non-Newtonian fluids are used in diverse applications such as additive to motor oils to improve lubrication, in shampoos and conditioners to improve texture, in manufacturing processes like injection moulding, and also in protective clothing and equipment to dampen high-velocity impacts.

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