Fluids

Introduction to fluids

There are three states of matter; solids, liquids, and gases. Of the three, liquids and gases come in the category of fluids. The tendency to flow, or in other words, the continuous and steady movement of liquids and gases, gives them the name of fluids.

We can find fluids all around us. The atmosphere is the blanket over our earth, and it is made up of gases such as oxygen and nitrogen. Two-third of the planet is covered in water. All living beings need water to survive. As we can see already, fluids are an integral part of the living processes.

Fluids in themselves are a significant area of study. The following article will talk about fluid mechanics, Newtonian and Non-Newtonian Fluids, and fluid dynamics.

Fluid Mechanics

To understand fluid mechanics, we need to start at the very basics and understand the terms – fluid and mechanics – separately.

The term fluid has been explained in the introductory paragraph. Any matter that can flow is called fluids. The water we drink at home and the oxygen we breathe are famous examples of fluids. Water is in liquid form, whereas oxygen is in gaseous form, and liquids and gases are the two matters called fluids.

On the other hand, mechanics is a branch of physical science that studies the behaviour of an object when it is subjected to forces. It is not just the behaviour of the object that is under study but also the various kinds of factors that are present and influencing it.

When the object under consideration is fluid, we call it fluid mechanics.

So we can say that fluid mechanics is a branch of physical science that studies the behaviour of fluids when it is at rest and in motion. Fluid mechanics can be subdivided into two broad categories, and they are fluid statics and fluid dynamics.

The study of fluids at rest is called fluid statics, whereas the study of fluids when it is in motion is called fluid dynamics.

Applications of Fluid Mechanics in daily life

Here are some real-life applications of fluid mechanics in daily life.

1. Fluid mechanics has made automobiles possible. Automobiles use fuel to power up their engine; fuels such as petrol and diesel are fluids. The understanding of these fuels and their working has enabled us to create cars, motorcycles, and what not.
2. Fluid mechanics is also behind the effective understanding of how blood is circulated inside our bodies. The movement of blood from the heart to other parts of the body and vice versa has fluid mechanics all over it. The invention of devices such as the blood pressure measuring machine is also because of fluid mechanics.
3. The piping design in our homes is also based on fluid mechanics. The water in our showers, taps, and the waste out of our sewers follow the principles of fluid mechanics.
4. Ships and boats are other popular examples where fluid mechanics are at work. Concepts like buoyancy and many other understandings made it possible. Aircrafts are also modelled on fluid mechanics.
5. Even nature follows the principles of fluid mechanics. The jellyfishes in the sea, the birds in the air, the butterflies in our garden all unknowingly apply these principles.

Another important concept that you will come across in fluid mechanics is that of Viscosity. Let us see what it is.

What is Viscosity?

Viscosity is an essential concept when it comes to fluid mechanics.

Viscosity can be understood as the resistance of a substance to flow. Viscosity determines how much fluidity a fluid has.

Let us understand it with an example.

Have you ever wondered why running through the air medium is easier than running in a pool of water? That is because of the inequality of viscosity in both mediums. Water has a higher viscosity than air which is a gas. The resistance of water is higher than air. The higher the viscosity, the more effort you have to put in, and the lesser the viscosity, the less effort you have to put in.

Substances that have low viscosity can flow and move easily, such as water, milk, and blood. Substances that have high viscosity – which means these substances will have strong resistance to flow – will move slowly, such as honey and glue.

You can also measure viscosity with the help of Newton’s law of viscosity. 

Newtonian Fluids and Non-Newtonian Fluids

Newton’s law of viscosity can measure the viscosity of various fluids. It is measured by dividing the shear stress by the rate of shear strain. Fluids that follow Newtonian law are called Newtonian fluids, and fluids that do not follow Newtonian law are called Non-newtonian fluids. Examples of Newtonian fluids are water, air, alcohol, glycerine, etc. and examples of non-newtonian fluids are quicksand, silly putty, and ketchup.

Fluid Dynamics

As mentioned already before, fluid dynamics is the branch of physical science that studies fluids in motion. In fluid dynamics, you can study the velocity of the fluids and lots of other factors that influence the movement of fluids. Concepts like the equation of continuity tell you how velocity and area are related to the movement of fluids. Bernoulli’s principle tells you about the relation between velocity and pressure. The momentum principle and the energy equation are some other important concepts that you learn in fluid dynamics.

All of these concepts together open up new interesting aspects of fluid dynamics, and there is much more to study. Learn more about fluid dynamics at Unacademy.

Conclusion

So fluids are matter that can flow. Liquids and gases come under fluids. In physical science, the study of fluids is called fluid mechanics. Mechanics studies the behaviour of an object when it is subjected to forces. The study of fluids at rest is called fluid statics, and the study of fluids in motion is called fluid dynamics. 

We also understood the meaning of viscosity. Viscosity is the resistance of a fluid substance. If the substance has a high viscosity, it will flow slowly, whereas if the substance has low viscosity, it will flow smoothly. 

We also learned about Newtonian Fluids. Fluids that follow Newton’s law of Viscosity are called Newtonian Fluids such as water and orange juice. Fluids that do not follow Newton’s law of Viscosity are called Non-Newtonian Fluids such as ketchup and silly putty.