FLUID MECHANICS & HEAT ENGINES

contentsFundamental conceptsApplicationsFundamental definitions Fundamental propertiesproblems

Importance of fluid mechanicsAll science including physics, chemistry, biology and mathematicsAll branches of engineering involving civil engineering, mechanical engineering, chemical , electrical, metallurgy , aerospace etc.

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

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

APPLICATIONS OF FLUIDSHYDROELECTRIC POWER PLANTSHYDRAULIC MACHINESAUTOMOBILESREFRIGERATION &AIR CONDITIONERSTHERMAL POWER PLANTSNUCLEAR POWER PLANTSOPERATING VARIOUS INSTRUMENTSHEAT ENGINES

What is fluid? What is mechanics?A substance that flows is called fluid. All liquid and gaseous substances are considered to be fluids.

Mechanics is the branch of applied physics that deals with motions.

FLUID MECHANICSFluid Mechanics is that branch of science which deals with behavior of the fluids at rest as well as in motion

THREE ASPECTS OF FLUIDSFLUID STATICS: The study of fluid at rest

FLUID KINEMATICS: The study of fluid in motion where pressure forces are not considered

FLUID DYNAMICS: The study of fluid if pressure forces is considered

FLUIDS & THEIR PROPERTIES

Density ()Density is the mass of the fluid per unit volume = m/v Units : Kg/m3

Specific Weight or Weight Density

It is defined as the weight per unit volume. It is usually denoted by w.W= xgSpecific volumeVolume per unit mass of fluidSpecific volume=1/ It is the reciprocal of mass densityIt is expressed as m3/kg

Specific Gravity(s):

The specific gravity is the ratio of the specific weight(density) of the fluid to the specific weight(density) of a standard fluid.For liquids ,standard fluid is taken as waterFor gases , standard fluid is taken as air.It is also called relative density. It is dimensionless and is denoted by S.

Problem 1. Calculate the specific weight , density and specific gravity of one litre of a liquid weighs 7N.

Ans: Specific weight =7000N/m3

Density=713.5Kg/m3

Specific Gravity=0.7135

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ViscosityProperty of a fluid which offers resistance to the movement of one layer of fluid over another adjacent layer of the fluid.Kinematic viscosityRatio between the dynamic viscosity and density of fluid

Newton's Law of viscosity

It states that the shear stress () on a fluid element layer is directly proportional to the rate of shear strain. The constant of proportionality is called the coefficient of viscosity.

Mathematically,= (du/dy)

Where, du/dy =velocity gradient = coefficient of viscosity, absolute viscosity or dynamic viscosity.

Fluid which obey newton's law of viscosity are known as Newtonian FluidsFluid which do not obeys newton's law of viscosity are known as non-newtonian fluids