01
FUNDAMENTAL
PROPERTIES OF
FLUIDS
Introduction
Fluid
A state of matter in
which molecules
move
e.g. liquids and gases
Engr. Christine Joy Bayato
SOLIDS
FLUIDS
- Molecules are tightly packed
- Elasticity as an important
property
- will initially deform, but will not
continuously deform when
acted by shearing stress
- Molecules are spaced
- Viscosity as an important
property
- deforms continuously when
acted by shearing stress of
any magnitude
Areas of
Applications
Human body
Cars
Piping and
Plumbing System
Industrial
Applications
Fluid Mechanics
study of fluids either in motion (fluid
dynamics) or at rest (fluid statics)
and the subsequent effects of the
fluid upon the boundaries, which
may be either solid surfaces or
interfaces with other fluids
Areas of
Applications
Natural flows
and weather
Boats
Aircraft and
spacecraft
Powerplants
Hydraulics
Hydrodynamics
experimental approach to fluid
mechanics from which
empirical formulas are derived
mathematical approach to fluid
mechanics where computations
are based on imaginary fluid that
is completely frictionless
(Analytical & Numerical)
02
Fluid Classification
Compressibility
the change in volume of a fluid
per unit change in pressure in
a constant temperature
process
Viscosity
a fluid’s
resistance to
flow
Note: In general, all fluids are
compressible but liquids have
negligible compressibility
TWO MAIN CLASSIFICATIONS
Ideal Fluids
incompressible, inviscid
(non-viscous) and exhibit
uniform velocity
distribution when flowing
Mass Density
measure of
concentration of
matter
Specific
volume
the volume
occupied by a
unit mass
Real Fluids
A. Newtonian – follows
Newton’s Law of
Viscosity; viscosity is
constant
B. Non-Newtonian Fluids –
viscosity is variable
03
Fluid Properties
Specific weight
The weight per
unit volume of a
fluid
Specific
Gravity
a dimensionless
ratio of a fluid’s
density to some
standard
reference density
Compressibility
fractional change in
the volume of a fluid
per unit change in
pressure in a constanttemperature process
Viscosity
Kinematic
Viscosity
property which
determines a
fluid’s resistance
to shear
ratio of the
dynamic viscosity
to its mass
density
Surface
Tension
Capillarity
membrane formed
when intermolecular
cohesive forces act
on the free surface
of the fluid
Ability of a liquid to
flow in narrow
spaces without the
assistance of
external forces
Bulk Modulus of
Elasticity
Celerity of
Pressure Wave
expresses the
compressibility of the
fluid
acoustic or sonic
velocity of a wave due
to pressure
disturbances
Ideal Gas Law
The equation of state
of a hypothetical ideal
gas
Boiling
formation of vapor bubbles within a fluid
mass; initiated when the absolute
pressure in the fluid reaches the vapor
pressure
Pascal
Vapor Pressure
the equilibrium pressure exerted
by the vapor form of a fluid just
above the liquid surface
Evaporation
occurs when the molecules at the
surface of a liquid placed in a container
open to atmosphere have sufficient
momentum to overcome the
intermolecular cohesive forces and
escape to the atmosphere
RECITATION
1
PA
m/s
Meter per
second
in
in
N
Newton
lbm
Pound
mass
cu.cm.
Cubic
centimeter
ha
hectare
s
seconds
atm
Atmosphere
gal
gallon
lbf
Pound force
μm
micrometer
L
liter
K
kelvin
kg
kilogram
mol
moles
bar
bar
RECITATION
2
ρ
density
σ
Surface
tension
Vs
Specific
volume
W
Weight
h
Capillary
rise
s
Specific
gravity
g
gravity
μ
viscosity
T
temperature
β
compressibility
dV
Change in
volume
P
Pressure
n
Number of
moles
EB
Bulk modulus of
elasticity
c
dP
Change in
pressure
Celerity
γ
Specific weight
m
mass
V
volume
Solution
04
SAMPLE PROBLEMS
Sample Problem 1
Show the conversion:
300 barr to kPa to atm
1 barr = 100 000 Pa
1 atm = 101 325 Pa
Solution
Sample Problem 2
Sample Problem 3
At what temperature will 0.654 moles of
neon gas occupy 12.30 liters at 1.95
atmospheres?
The specific weight of water at ordinary
pressure and temperature is 62.4 lb/ft3. The
specific gravity of mercury is 13.56.
Compute the density of water and the
specific weight and density of mercury.
Solution
Solution
Sample Problem 4
Solution
Sample Problem 5
Sample Problem 6
A distance between the moving plate and
fixed plate is 0.025 mm, the velocity of
moving plate is 60 cm/s, requires a force of
2 N/m2 (shear stress). Determine the fluid
viscosity between the plates?
Solution
Solution
Sample Problem 7
Determine the specific gravity (S) of a fluid
having a dynamic viscosity (μ) is 0.05 poise
and kinematic viscosity 0.035 stokes?
Solution
Sample Problem 8
SEATWORK 1
Calculate the diameter of a capillary tube that is
six inches long if you want the fluid to rise to
the top of the tube. Assume the fluid is water
with a surface tension of 0.1 N/m, specific
weight of 9.8kN/m3, and a contact angle of zero
degrees.
A small village draws 1.5 acre-foot of water
per day from its reservoir. Convert this
water usage into
(a) gallons per minute; and
(b) liters per second.
(Use the shown unit conversion)
Solution
Solution
SEATWORK 2
Calculate the density, specific weight, and
specific volume of chlorine gas at 25.3°C
and pressure of 601.4 kN/m2 abs where
R=117.1 Nm/kgK.
Solution
SEATWORK 3
SEATWORK 4
The specific weight of water at ordinary
pressure and temperature is 9.81 kN/m3. The
specific gravity of mercury is 13.56.
Compute the density of water and the
specific weight and density of mercury
Consider a container of heavy cream which
has a density of 1005.2 kg/m3. If we whip
the cream to three times its volume, what is
the specific gravity and specific weight of
the whipped cream?
Solution
Solution
SEATWORK 5
A flat plate of area 1.5×106 mm2 is pulled
with a speed of 0.4 m/s relative to another
plate located at a distance of 0.15 mm from
it. Find the force and power required to
maintain this speed , if the fluid separated
them is having viscosity as 1 poise.
Solution
SEATWORK 6
Determine the viscosity of a liquid having
kinematic viscosity 6 stokes and specific
gravity 1.9?
SEATWORK 6
Calculate the capillary effect in millimeter in a
glass tube of 4 mm diameter, when immersed in
(1) water , and (2) mercury. The values of the
surface tension of water and mercury are
0.073575 N/m and 0.51 N/m respectively. The
angle of contact for mercury 1.30o.
Solution
Question
& answer