Properties of fluid.ppt

PROPERTIES OF FLUID

NISHCHAL GIRI

CONTENTS:- PROPERTIES OF FLUID VISCOSITY APPLICATION OF VISCOSITY SURFACE TENSION APPLICATION OF SURFACE TENSION CAPILLARY ACTION APPLICATION OF CAPILLARY ACTION CONCLUSION

PROPERTIES OF FLUIDS:-

Matter exists in two states- the solid state and the fluid state. This classification of matter is based on the spacing between different molecules of matter as well as on the behavior of matter when subjected to stresses. Because molecules in solid state are spaced very closely, solids possess compactness and rigidity of form. The molecules in fluid can move more freely within the fluid mass and therefore the fluids do not possess any rigidity of form.

THE PROPERTIES OF FLUIDS ARE:-

VISCOSITY SURFACE TENSION COMPRESSIBILITY

VISCOSITY :-

Viscosity is a measure of a fluid's resistance to flow. It describes the internal friction of a moving fluid. A fluid with large viscosity resists motion because its molecular makeup gives it a lot of internal friction. A fluid with low viscosity flows easily because its molecular makeup results in very little friction when it is in motion. Gases also have viscosity, although it is a little harder to notice it in ordinary circumstances.

APPLICATION OF VISCOSITY :-1. Transparent and storing facilities for fluids ie,

pipes, tanks2. Bitumen used for road construction.3. Designing of the sewer line or any other pipe

flow viscosity play an important role in finding out its flow behaviour.

4. Drilling for oil and gas requires sensitive viscosity.

5. To maintain the performance of machine and automobiles by determining thickness of lubricating oil or motor oil.

TO MAINTAIN THE PERFORMANCE OF MACHINE AND AUTOMOBILES:- Oil viscosity needs to suit the right ambient

temperatures. If it’s too thick when the engine is cold, it won’t move around the engine. And if it becomes too thin when the engine is hot, it won’t give the right protection to the engine parts.Optimising an oil’s viscosity, or thickness, helps maximise energy efficiency while avoiding component wear. Viscosity modifiers increase the viscosity of your oil at high temperature but have little effect on low-temperature viscosity. These enable your oil to flow properly when cold and also to remain thick enough to protect your engine components at high temperatures.

Lower-viscosity grades of oil such as Shell Helix Ultra, make it easier for your engine to start from cold because they present less resistance to moving parts and hence take less power from your engine. This also means that you get enhanced fuel economy.

TYPES OF VISCOMETER :-

Laboratory viscometers for fluid U-tube Falling sphereFalling Piston ViscometersFalling Sphere Viscometers

U-TUBE MANOMETER

Pressure measuring devices using liquid columns in vertical or inclined tubes are called manometers. One of the most common is the water filled u-tube manometer used to measure pressure difference in pitot or orifices located in the airflow in air handling or ventilation system.

pd = γ h     = ρ g h       wherepd = pressureγ = specific weight of the fluid in the tube (kN/m3, lb/ft3 )ρ = density (kg/m3, lb/ft3)g = acceleration of gravity (9.81 m/s2, 32.174 ft/s2)h = liquid height (m, ft)

SURFACE TENSION

Surface tension is a contractive tendency of the surface of a fluid that allows it to resist an external force. Surface tension is an important property that markebly influences the ecosystems.

Whenever a fluid is left to itself, the fluid tends to attend the minimum surface area possible. The reason behind this is that while a molecule inside the fluid is pulled in each and every direction by the adjacent molecules in the surface of the fluid , the case is different. the adhesive forces causes downward pull on the molecule due to cohesent. So the molecule on the surface tends to move down but it is repelled by the molecules below it.

FORMULA USED TO CALCULATE SURFACE TENSION :-

Where,Where,  γ = surface tension  θ = contact angle  ρ = density g = acceleration due to gravity r = radius of tube

The magnitude of repulsive forces per unit length is called surface tension or coefficient of surface tension.

 σ = F/L

APPLICATION OF SURFACE TENSION :-

A water strider can walk on water. Some tent are made impermeable

of the rain but they are not really impermeable, but if water is placed on it then the water doesn’t pass through the fine small pores of the tent cover. But as you touch the cover while water is on it, you break surface tension and water passes through.

CAPILLARY ACTION :-

Capillary action is the ability of a fluid to flow in narrow spaces without the assistance of, and in opposition to, external forces like gravity.

A common apparatus used to demonstrate the first phenomenon is the capillary tube. When the lower end of a vertical glass tube is placed in a fluid, such as water a concave meniscus forms. Adhesion occurs between the fluid and the solid inner wall pulling the fluid column up until there is a sufficient mass of fluid for gravitational forces to overcome these intermolecular forces. The contact length between the top of the fluid column and the tube is proportional to the diameter of the tube, while the weight of the fluid column is proportional to the square of tube’s diameter. So, a narrow tube will draw a fluid column higher than a wider tube will.

APPLICATION OF CAPILLARY ACTION :-

Capillary action is found in thermometer where fluid used in it automatically rises when comes in contact with higher temperature or falls down with lower ones.

Capillary action can be performed to transfer fluid from one vessel to another on its own.

Capillary action can be experienced in the half dipped cloth as well as on lantern.

CAPILLARY ACTION ON LANTERN :-

Capillary action works by drawing the kerosene/oil out of the fount to the tip of the wick where the flame heats the oil to a gas and ignites it.

When one end of the cloth kept in contact with the oil and another at the top to burn, the oil rises upward with the help of the cloth. Due to the capillary action, the oil simply travels to the top and ignites