Fluid Mech.Intro.pptx civil ajhdjdnsjbsbsbsn

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1. FLUIDS AND THEIR PROPERTIES

2. 1.What is Fluid? Fluid is a substance that is capable of flowing. It has no definite shape of its own. It assumes the shape of its container. Substance that deforms continuously when sheared. Both liquids and gases are fluids. Examples of fluids are : i . water ii. milk iii. kerosene iv. petrol v. emulsions etc. 4/25/2024 2

3. 2.DIFFERENCE BETWEEN SOLID , LIQUID AND GAS 4/25/2024 3

4. 3. Properties of Fluids Properties of fluids determine how fluids can be used in engineering and technology. They also determine the behaviour of fluids in fluid mechanics. They are: Density Viscosity Surface Tension Capillary Action Specific Weight Specific Gravity 4/25/2024 4

5. 3.1 density Density is the mass per unit volume of a fluid. In other words, it is the ratio between mass (m) and volume (V) of a fluid. Density is denoted by the symbol ‘ρ’. Its unit is kg/m 3 . 4/25/2024 5

6. Mass : Amount of matter in an object, stays the same everywhere, measured in kilograms (kg) or grams (g). Weight : Force of gravity on an object, varies with location, measured in newtons (N) or pounds (lb) 4/25/2024 6 Ship and Water : A ship floats on water because it displaces an amount of water equal to its weight. The ship floats because its density is less than that of water. If the ship were denser than water, it would sink. Hot Air Balloon : A hot air balloon rises in the air because the density of the hot air inside the balloon is less than the density of the cooler air outside. This buoyant force causes the balloon to float upward. Ice Cubes and Water : Ice cubes float in water because ice has a lower density than liquid water. The solid ice occupies more volume than the same mass of liquid water, which causes it to float. Oil and Water : Oil floats on top of water because oil has a lower density than water. When oil is poured into water, it forms a distinct layer on the surface due to its lower density. E xamples to understand density in real life

7. 3.2 Viscosity Viscosity is the fluid property that determines the amount of resistance of the fluid to shear stress. It is the property of the fluid due to which the fluid offers resistance to flow of one layer of the fluid over another adjacent layer. 4/25/2024 7

8. 3.2.1 Dynamic Viscosity The Dynamic (shear) viscosity of a fluid expresses its resistance to shearing flows, where adjacent layers move parallel to each other with different speeds.  4/25/2024 8 SI physical unit of dynamic viscosity (μ) is the Pascal-second (Pa s) μ = =10 poise; named after Jean Poiseuille  

9. 3.2.2 Kinematic Viscosity The kinematic viscosity (also called "momentum diffusivity") is the ratio of the dynamic viscosity  μ  to the density of the fluid ρ . 4/25/2024 9 The SI unit of kinematic viscosity is square meter per second ( /s ) v = /s =1 stoke; named after Sir George Gabriel Stokes.  

10. 3.3 Surface Tension The property of fluids to resist tensile stresses on their surface is called as Surface Tension. 4/25/2024 10

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12. 3.4 Capillary Action Capillary action is the property of fluid to flow in a narrow spaces without assistance of and in opposition to external forces like gravity. The effect can be seen in the drawing up of liquids between the hairs of a paint-brush, in a thin tube, in porous materials such as paper and plaster, in some non-porous materials such as sand or in a cell. It occurs because of intermolecular forces between the liquid and surrounding solid surfaces. 4/25/2024 12

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14. 3.5 Specific Weight Specific weight is the weight possessed by unit volume of a fluid. It is denoted by ‘w’. Its unit is N/m 3 . Specific weight varies from place to place due to the change of acceleration due to gravity (g). 4/25/2024 14

15. 3.6 Specific Gravity Specific gravity is the ratio of specific weight of the given fluid to the specific weight of standard fluid. It is denoted by the letter ‘S’. It has no unit. 4/25/2024 15

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17. 4. Types of Fluids Fluids can be classified into five basic types. They are: Ideal Fluid Real Fluid Pseudo-plastic Fluid Newtonian Fluid Non-Newtonian Fluid 4/25/2024 17

18. 4.1 Ideal Fluid An Ideal Fluid is a fluid that has no viscosity. It is incompressible in nature. Practically, no ideal fluid exists. 4/25/2024 18

19. 4.2 Real Fluid Real fluids are compressible in nature. They have some viscosity. Real fluids implies friction effects. Examples: Kerosene, Petrol, Castor oil 4/25/2024 19

20. 4.3 Pseudo-plastic Fluid A fluid whose apparent viscosity or consistency  decreases instantaneously with an increase in  shear rate. Examples are: i . quick sand ii. ketch-up etc. 4/25/2024 20

21. 4.4 Newtonian fluid Fluids that obey Newton’s law of viscosity are known as Newtonian Fluids. For a Newtonian fluid, viscosity is entirely dependent upon the temperature and pressure of the fluid. Examples: water, air, emulsions 4/25/2024 21

22. 4.5 Non-Newtonian Fluids Fluids that do not obey Newton’s law of viscosity are non-Newtonian fluids. Examples: Flubber , Oobleck (suspension of starch in water), Pastes, Gels & Polymer solutions. 4/25/2024 22

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