FLUID MECHANICS Presented by KEERTHI KUMARI B M

FLUID MECHANICS Presented by KEERTHI KUMARI B M. Tech , Assistant Professor DEPARTMENT OF MECHANICAL ENGINEERING VISAKHA INSTITUTE OF ENGINEERING & TECHNOLOGY

FLUID MECHANICS Fluid Mechanics is that branch of science which deals with behaviour of the fluids at rest as well as in motion

Fluid mechanics can we divided into 3 divisions: Hydrostatics: that studies the mechanics of fluids at absolute and relative rest. Kinematics: deals with translation, rotation and deformation of fluid without considering the force and energy causing such a motion. Dynamics: that prescribes the relation between velocities and acceleration and the forces which are exerted by or upon the moving fluids.

What is Fluid ? Matter exist in two principal forms: • Solid • Fluids are further sub-divided into: • Liquid • Gas

For all practical purposes , the liquids and solids can be regarded as incompressible. This means that pressure and temperature have practically no effect on them. Eg Water, Kerosene, petrol etc. But Gases are readily compressible fluids. They expand infinitely in the absence of pressure and contract easily under pressure. Eg air , ammonia etc.

A DAY FULL OF FLUID MECHANICS

YOU WOKE UP IN THE MORNING AND THE ROOM IS COOL. Coolant circulating Inside it and cool Air which it gives is Fluid

After that you washed your face at the sink. The water which comes at your tap is fluid and has come through the piping system which also comes under fluid mechanics.

After that you decided to have your breakfast. The coolant moving inside the small pipes at the back of your refrigerator, and the air circulating inside it are both fluids.

After finishing your breakfast, You decided to do some cleaning before heading to the school. Proper suction of air and filtering the dust requires the knowledge of Fluid Mechanics.

After that you turned on your T. V to get the morning news. Nothing good, war again

UNMANNED AIR VEHICLE USED BY US ARMY IN AFGHANISTAN

MISSILE AERODYNAMICS

Now it’s the time to go to college, otherwise you will get late A mixture of fuel like petrol and air is forced by atmospheric (or greater) pressure into the cylinder through the intake port

Before your class you went to PC lab and took a print out of your assignment. Inkjet printing also involves fluid mechanics.

Knowledge of Fluid Mechanics is essential for proper design of Ships.

Otherwise without the proper knowledge of fluid mechanics, What will happen

In this subject, topic on Model Studies is there which is very important for civil engineers. Model Tests on civil engineering structures such as Dams, canals to predict the working of full size structure and river models assist a civil engineer in the design of flood control structure as well as in the analysis of sediment movement in rivers.

Significance of Fluid Mechanics • Design of wide range of hydraulic structures • • • (dams, canals) and machinery ( pumps, turbines). Fluidic control devices; both pneumatic and hydraulic. Design and analysis of gas turbine , rocket engine, super sonic aircrafts. Human circulatory system i. e the flow of blood in veins and the pumping action of heart.

Ideal Fluid: A fluid is said to be ideal if it is assumed to be both incompressible and inviscid (nonviscous). Ideal fluid has no surface tension and viscosity is zero and no frictional forces are set up even during the fluid motion. Ideal Fluids are imaginary and do not exist in nature.

Real Fluid: Practical Fluid have surface tension, viscosity and compressibility. Whenever motion takes place, the tangential or shear forces always come into play due to viscosity and some frictional work is done.

Density ( ) Density is the mass of the fluid per unit volume = m/v Units : Kg/m 3

Specific Gravity(s): The specific gravity is the ratio of the density or specific weight of the fluid to the density or specific weight of water, at a temperature of 4 o. C For Gases the standard fluid is taken either air at 00 C or Hydrogen at the same temperature.

It is dimensionless quantity. A Statement that the specific gravity of mercury is 13. 6 implies that its weight (or mass) in 13. 6 times that of the same volume of water. In simple words, mercury is 13. 6 times heavier than water.

Specific Volume: Represents the volume per unit mass of fluid. Specific Volume is the inverse of the mass density. v= V/m or v=1/ The concept of specific volume is found to be more useful in the study of flow of compressible fluids i. e gases.

Viscosity: It is the property of the fluid by virue of which it offers resistance to shear or angular deformation. Mollases, tar, glycerine are highly viscous fluids. Water, air, petrol have very small viscosity and are called thin fluids.

Newton’s Law of Viscosity = (du/dy) Where, du/dy =velocity gradient = coefficient of viscosity, absolute viscosity or dynamic viscosity.

Following Observations can be made from Newton’s viscosity Equation: • Max. shear stress occur when velocity gradient is largest and shear stress disappears where velocity gradient is zero. • Velocity Gradient becomes small with distance from the boundary. Consequently the max value of shear stress occurs at the boundary and it decreases from the boundary.