Fluid Properties - Fluid Mechanics | Properties of water

Fluid Properties – Fluid Mechanics | Properties of water

The solid object can certainly range tensile stress, compressive stress and shear stress but fluid can not. For not conveying shear stress the structure of the fluid properties is change and one layer flows over the other layer. The intermolecular forces of a solid substance are more, on the other hand in case of liquid substance it is comparatively less, that’s why the atom in the liquid stays far from one another. Therefore, though the liquid has a definite volume, it has no structure and can move freely.

Definition of fluid

The atoms and molecules of those substances which can gain speed easily and able to move not being isolated is called fluid. If a part of a substance, not being isolated from another part, atoms and molecules gain speed easily and able to move one place to another is called fluid.

Name the three types of fluids and properties

Fluid mainly three types. Like

Liquid

It is such a state of a substance that turns into a liquid at a specific temperature. Such as- water is in ice state or solid-state at 0° C temperature. When its temperature increases into 4°C then it turns into liquid. Its basic characteristic is that it holds the same shape of its container and it cannot be compressed.

Properties of liquid

  • In the static condition, it stays on the free horizontal surface.
  • It presses vertically on the body of the container.
  • Inside it, the stress is equal at any point.
  • It has a definite volume but no definite shape.
  • It does not obstruct in its own shape change.
  • It can not be compressed.
  • With the change of temperature, its size is not changing much.

Gas

It is a very thermal state of the substance. When heat provides to any substance then it turns into a gas from the liquid state. For example- when water is improved 100°C by providing heat, then it turns into a gas.

Vapour

Naturally, every liquid wants to turn into vapour. That is to say, to change into a gas from liquid. The atoms of the free water surface turned into vapour by flowing outwards continuously. Its condition changes with the changes in temperature. Its qualities are mostly like the qualities of gas, it is easily compressive and it has no free surface.

Properties of Gas and Vapour

  • It does not have any free surface.
  • It cannot be compressed easily by pressure.
  • Gas or vapour of any volume occupies the whole container.
  • It presses vertically on the body of the container.
  • Its expansion coefficient is much.
  • It does not obstruct in changing its own shape.
  • Its expansion power is much.

Properties of water

  • In stagnant conditions, the surface of the water stays at the same flat surface if not affected by air.
  • Water applies the same pressure at every side of a point.
  • The velocity of water is proportional to the bed slope of the bottom of the channel.
  • The velocity of water in any channel depends on the bottom and its roughness of the side of channels. As much the bottom and its side become smooth, the velocity of water is increased much.
  • The pressure of water at any point is equal to the weight of water on this point and it increases with the increase of deepness of water.
  • The velocity of water is much in the center than the side in a channel.
  • At zero pressure no water can stay in a liquid state.

Difference between the liquid, vapor and gas

Liquid, vapor and gas have some differences, which have shown below. This also called the characteristics of a fluid.

Properties of liquid
LiquidVaporGas
It does not interfere in its own shape change.It also does not interfere in its own shape change.It also does not interfere in its own shape change.
It obstructs much in compressing. It is easy to compress.It can be compressed very easily.
Its condition does not change much with the changes of temperature. Its state changes with the change of temporary.It is noticed that with the changes of temperature, its state changes much.
In normal state its elasticity is noticed but save energy like solid substance. Its state changes with the change of temporary. In compressed state its viscosity is much less, that’s why energy saving is also less.
Its viscosity decreases due to raising temperature. Viscosity increases gradually due to raising temperature. Viscosity increases rapidly with the temperature raising.
Its expansion coefficient is very low. Its expansion coefficient is much.Its expansion coefficient is very much.
In static state it stays in horizontal free surface. It has no free surface. It has no free surface.
It presses vertically on the container. It also press vertically. It also press vertically.
For shearing stress it becomes distorted and in a specific time this distorted stress is proportional to it. Due to shearing stress it becomes distorted and in a certain time this distorted stress is not proportional to it. Due to shearing stress it becomes distorted and in a certain time this distorted stress is not proportional to it.

General properties of fluids (liquid)

  1. Density
  2. Specific weight
  3. Specific gravity
  4. Compressibility
  5. Surface tension
  6. Capillarity
  7. Viscosity

Definition of Density

If the density of an object is known, it can guess whether another object is heavier or lighter from it. At standard temperature measurement and pressure, the mass of a single volume in any liquid substance is called its density. The density of water is most at 4°C temperature. The density of water becomes so less with the change of pressure and temperature that, in every real application it is ignored. The density is expressed with Ρ (rho).

Definition of Specific weight or volume

The weight of the single volume of any liquid substance is its specific weight. With the change of pressure and temperature, its value also changes. But the specific difference of water with the specific difference of temperature measurement and pressure is so less that, in reality, it is ignored. It also is known as weight density and it can be expressed with ω.

What is Specific gravity?

The ratio of the weight of any object and the weight of the same volume of pure water at 4°C temperature is called the specific gravity of that object. So the specific gravity of any flowing object is the ratio of the weight of that object and the weight of the same volume pure water at 4°C temperature. Specific gravity is only a number it has no unit. It is expressed with S. At 4°C temperature, the specific gravity of water is 1 and mercury is 13.59.

What is Compressibility?

The changing of the volume of liquid substance due to pressure is called its compressibility. The compressibility of water is so less that it is ignored in a real application. So water is considered an incompressible substance.

Definition of Surface tension

If two liquid of different density or a gas and a liquid stay interconnected with each other, surface contact creates a curve line which is known as the meniscus. This curve surface is created for the atomic attraction. The surface works as an elastic skin and that has tension on both sides. This tension is known as surface tension. It is created in the bubble of spirit level and soap.

What is Capillarity?

Capillerity of water

If a glass tube with an exquisite and balanced hole is sunk in the water, it is seen that the water rises up through the tube. In which case of liquid, the glass tube gets wet, in case of that liquid it happens. (Figure shown). The substance in which the glass tube doesn’t get wet, such as mercury or some kind of liquid the surface of liquid gets down. (Figure shown). In the case of water, the surface of the substance gets down and in case of mercury it gets up. The up-down of the liquid through the thin pipe is called capillarity. The thin tube is called a capillary tube. Capillary ascertains adhesion of liquid substance with the surface and cohesion of being connected to the atoms of liquid substance, with it the surface tension of liquid substance can be measured. In the following Figure shown. a glass tube with an exquisite and balanced hole is sunk into water or such a liquid that can wet the glass tube. In this case, the liquid gets raised into the tube than the outer level and the surface concaves downwards. This is because, the cohesion of staying connected of the atoms of liquid substance is more than the adhesion of liquid with the tube, If the touch angle is less than 90° then the surface tension raises the liquid substance of the tube and if it is more than 90° then surface tension pulls the liquid substance of the tube downwards. On the nature of the liquid substance and on the diameter of the tube the up-down of the liquid depends.

What is viscosity of water?

Viscosity

Two different liquid substances such as- water and chit molasses, if they are kept by side and let them flow, it will be seen that the flow velocity of water is more than the chit molasses. The reason is the velocity difference of the above two liquid substances. Here, the velocity of chit molasses is more, on the other hand the velocity of water is less. So, velocity is such properties of liquid substance which controls the rate of its flow. Velocity in other words- the cohesion among the atoms of different layers of the same liquid substance which controls the rate of the fluid during flowering. The properties for which the liquid substance prevents the relative motion between different layer is viscosity.
The liquid substance consists of numerous atoms. All these atoms attract each other, this attraction is known as an atomic attraction. If the atomic attraction of a liquid is much, the viscosity is also much but flows are less. Such as- tar. On the other hand, which liquid substance has a less atomic attraction, the viscosity of that is also less but the flows are much. Such as- water. Viscosity is related to temperature. If temperature is rising the viscosity becomes less. But if the temperature rises the viscosity of gas is also rises. The force that is needed to move into a unit distance parallelly a flat surface with a unit area in a unit velocity to other surfaces is called dynamic viscosity or absolute viscosity.
The gap between the two surfaces has to fill up with fluid properties. This viscosity is expressed with- The ratio that crates with a dynamic viscosity of its mass density of a fluid is called kinematic viscosity.

Omar Faruk

I am Omar Faruk, the owner of Engineers Advice. He is a person who always tries to invent something new & share that others. He loves to write about Mechanical, Electrical and Electronics related content. He has completed his diploma from the Department of Mechanical and graduation from the Department of EEE.

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