fluid properties

1. Gokhale Education Society’s
RH SAPAT COLLEGE OF ENGINEERING
Management studies and research
Prin. T.A.Kulkarni,Vidyanagar, Nashik- 422 005.
Department of Civil Engineering.
SE CIVIL
FLUID MECHANICS (2019 Pattern)
Unit I- Properties of Fluids & Fluid Statics
Presented By
Mrs.S.M.Kale,
Assistant Professor,
Department of Civil Engineering,

2. UNIT-I a) Properties of Fluids: Definition of fluid and fluid mechanics: examples
and practical applications, classification of fluids: Real and Ideal, physical properties
of fluids: mass density, specific weight, specific volume, relative density,
viscosity,Newton’s law of viscosity Dynamic and kinematic
viscosity,compressibility,cohesion,adhesion,surfacetension,capillarity,vapour,pressure
b) Fluid Statics: Basic equation of hydrostatics, concept of pressure, pressure
head,Pascal’s Law, measurement of pressure (absolute, gauge), principle of
manometers: Balancing liquid column, dead weight, pressure transducers and their
types, total pressure and centre of pressure: on plane horizontal, vertical, inclined and
curved surfaces:practical applications, Buoyancy and Floatation: Principle of
floatation and buoyancy,stability of floating and submerged bodies

3. Definition of Fluid and Fluid Mechanics
1. Substance which is capable of flowing.
2. It is substance which deforms continuously when
subjected to an external shearing force.
Fluid Mechanics
Fluid Statics
(Fluid at rest)
Fluid Dynamics
(Fluid in motion)
Fluid Kinematics
(Fluid in motion)
Without considering the forces acting
on fluid in motion
Considering the forces acting on fluid
in motion

4. Liquid Vapour/steam
Gas/Air
Fluid
• Liquid has definite volume but no definite shape
• Gas possesses no definite volume. It is compressible.
• Vapour is a gas whose temperature is near to liquid.
Q.1) Enlist some of the fluids you encountered in daily life.
Q.2) Differentiate between liquid and gases.

5. 1. Mass Density or Specific Mass ( ρ )rho ρ =
𝒎𝒂𝒔𝒔
𝒗𝒐𝒍𝒖𝒎𝒆
 Density of water, ρw
2. Specific Weight or Unit weight (γ )gamma γ =
𝑾𝒆𝒊𝒈𝒉𝒕
𝒗𝒐𝒍𝒖𝒎𝒆
 Specific weight of water, γw
 IMP Relationship
3. Specific Volume v=
𝑽𝒐𝒍𝒖𝒎𝒆
𝑴𝒂𝒔𝒔
 Inverse of mass density.
 v=
𝟏
ρ
Dimension SI Unit CGS Unit
ML-3 1000 Kg/m3 1 gm/cm3
Dimension SI Unit CGS Unit
ML-2T-2 9810 N/m3 1 dyne/cm3
γ = ρg

6. 4. Specific Gravity or Relative Density
S=
Specific Weight of fluid
Specific Weight of Standard fluid
=
𝑫𝒆𝒏𝒔𝒊𝒕𝒚 𝒐𝒇 𝒇𝒍𝒖𝒊𝒅
𝑫𝒆𝒏𝒔𝒊𝒕𝒚 𝒐𝒇 𝒔𝒕𝒂𝒏𝒅𝒂𝒓𝒅 𝒇𝒍𝒖𝒊𝒅
S =
γ
γw
S =
ρ
ρw
 Standard liquid –Water
 Specific Gravity of water : S= 1 at 40C @ STP
 Specific Gravity is a dimensionless number,
 S< 1 lighter liquid. e.g. kerosene S= 0.8
 S > 1 Heavier liquid. e.g. mercury S= 13.6

7. Phenomenon related to viscosity
 Liquids like glycerine or honey, flow very slowly
compared to water, petrol, oil, why?
 Why do water spilled on floor wet the floor?
 Phenomenon of Molten Volcano lava flowing and its
stoppage.

8. Viscosity is defined as the property of a fluid which offers resistance to the
movement of one layer of fluid over another adjacent layer of the fluid.
𝜏 = 𝝁
𝑑𝑢
𝑑𝑦
(Newton’s Law of viscosity)
Where,  = shear stress
μ = coe.of viscosity
or
dynamic viscosity
or
absolute viscosity
𝑑𝑢
𝑑𝑦
= velocity gradient
or
shear strain

14. Summary
 Fluid is a substance which is capable of flowing.
 Fluid mechanics is a branch of engineering science which deals with the
study of fluid under the condition of rest or in motion.
 Mass density is mass per volume while weight density is weight per volume
 Specific gravity is ratio of specific weight of fluid to specific weight of
standard fluid.
 Specific volume is inverse of specific mass.
 Viscosity of liquid decreases as temperature increases while for gases it
decreases as temperature increases.
Key words
 Fluid, fluid mechanics, mass density, weight density, specific gravity.,
viscosity

15. Quiz
1) The branch of Engineering science which deals with study of fluid at rest.
a) Fluid kinematics b) fluid dynamics c) fluid statics d) All of above.
Ans: c) fluid statics
2) The ratio of specific weight of fluid to specific weight of standard fluid.
a) Specific volume b) specific gravity c) Relative density d) b and c both
Ans: d) b and c both
3) Relation between mass density and weight density.
a) Mass density= weight density x g
b) Weight density= mass density x g
c) Mass density= weight density
d) None of above
Ans: Weight density= mass density x g

16. 4) Viscosity of liquid ---------- with temperature
a) Increases
b) Decreases
c) Remains same
d) None
Ans: b) Decreases

17. Thank you