Topic 1 - Fluid Characteristic

8/20/2019 Topic 1 - Fluid Characteristic

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DCC5143 – FLUID MECHANICS

Civil Engineering Department


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UNIT CONVERSION

mm – cm – m – km

10 – 100 - 1000

mg – cg – g – kg

Small to big – divide

Big to small - multiply

1000 liter = 1 m3

m2

– cm2

1m – 100 cm

1m2 – (100 cm)2

1m3 – (100 cm)3

1 kg/m3 – g / cm3

1 kg x 1000 g x (1 m)3

m3 1kg (100 cm)3

0.001 g/cm3


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Exercise

1. 36 km/hour to m/s

2. 64 kg/m3 to gm/cm3

3. 463 liter/hour to m3/s

4. 10 l/s


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DCC5143 Fluid Mechanics (4 cr)

• Fluid Characteristics

• Measurement of Pressure

• Hydrostatic Force

• Buoyancy and Stability

• Hydrodynamics

• Flow Measurement and Bernoulli Equations

• Fluid Flow

• Momentum Equations


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Assesment

• Test (2) – 20%

• Quiz (2) – 10 %

•

Assignment (1) – 10 %• Presentation (1) – 10 %

• Total = 50%


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TOPIC 1

FLUID CHARACTERISTIC


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HYDRAULICS

Hydraulics (from the Greek word for water) is thestudy of the problems of the flow and storage ofwater, but is often applied to other liquids.

Fluid -


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FLUIDS MECHANICS

Fluid mechanics is the section of applied mechanics

concerned with the statics and dynamics of liquids and gases.

Fluid mechanics is study about behaviour of fluid when

there is changes on it.

STATIC DYNAMICS

GASES


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PHYSICAL CHARACTERISTICS OF LIQUID AND

GAS

There are three states of matter: solids, liquids and gases.

Both liquids and gases are classified as fluids.

Fluids do not resist a change in shape. Therefore fluids assume

the shape of the container they occupy.

Liquids may be considered to have a fixed volume and therefore

can have a free surface. Liquids are almost incompressible.

Conversely, gases are easily compressed and will expand to fill a

container they occupy.

We will usually be interested in liquids, either at rest or in motion.


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PHYSICAL CHARACTERISTICS OF LIQUID AND GAS

LIQUID GAS

Particles are close together with no

regular arrangement

Well separated with no regular

arrangement

Vibrate, move about, and slide passedeach other

Vibrate and move freely at high speed

Follow shape container Fills any space

Fixed volume No definite volume


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PHYSICAL PROPERTIES OF FLUIDS

DENSITY ( )

(rho) is mass per unit volume, units kg/m3

SPECIFIC WEIGHT ()

w is the weight per unit volume, units N/m3

weight = mass x gravitational acceleration

SPECIFIC GRAVITY ( @ SG)

or relative density is the ratio of the density of a substance to

the density of water.SPECIFIC VOLUME (v/m @ 1/ )

The volume per unit mass , units m3 /kg.


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WHAT’S THE DIFFERENCE BETWEEN

MASS AND WEIGHT?

MASS (m)

Mass is defined as the amount of matter an object has,

unit kg.

WEIGHT (W)

Weight of an object on earth depends on the force of attractiongravity between object and earth, unit N.


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DENSITY

The mass per unit volume of a substance, usually denoted as ρ . Typical

values are:

• Water: 1000 kg/m3;

• Mercury: 13600 kg/m3;

• Air: 1.23 kg/m3;


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SPECIFIC WEIGHT

The weight of a unit volume a substance, usually denotedas γ . Essentially density times the acceleration due togravity:

= ρ g


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Relative Density (Specific Gravity)

A dimensionless measure of the density of a substance with

reference to density of some standard substance, usually

water at 4°C:relative density = density of substance/density of water

= specific weight of substance/specific

weight of water


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Problems - Properties

a) If 6 m3 of oil weights 47 kN, find its specific weight,density, and relative density.

(Ans. 7.833 kN/m3 , 798 kg/m3 , 0.800)

b) Calculate the relative density, density and specificweight of an oil which are 7.3 m3 in volume and6500kg in mass.

(Ans. 0.89, 890.41 kg/m3 , 8734.93N/m3 )


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Problems - Properties

c) A rectangular container size 250 x 300mm x1500mm and has a mass30kg

Calculate ;

i) Density

ii) Weight

iii) Specific weight

iv) Specific gravityv) Specific volume

d) A liquid volume is 1500 liter fill up a cylinder with diameter 50 cm. Ifthe weight of the liquid is 20 N

Calculate ;i) Density

ii) Specific weight

iii) Specific gravity

iv) Specific volume

v) High of the cylinder


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Problems

1. Define each characteristics below including its SI unit:

a) Density

b) Gravity specificc) Weight

d) Specific weight

e) Dynamic viscosity

f) Kinematic viscosity

2. A specific gravity for a liquid is 0.87. What is the density for the

liquid?

3. 150 N of oil is placed into a container with volume 0f 0.017 m3.

Calculate the density of the oil.

4. A dynamic viscosity and specific gravity for a liquid is o.495 kg/ms

and 0.9 respectively. Calculate the kinematic viscosity for the

liquid.


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5. A fluid with mass of 7500 kg fill an open cylinder container with

200cm diameter and 300cm height. Calculate the;

a) Density

b) Gravity specific

c) Specific volume

6. A liquid has a volume 1500 liter fill up into a cylinder has adiameter 100 cm. The weight of the liquid is 0.5 kN. Determine;

a) Density

b) Specific weight

c) Specific gravityd) Specific volume

e) Height of cylinder


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7. 8540 N fluid completely fills into a rectangular container . The container

has a length of 110 cm, width of 80cm and height of 150 cm. Calculate

the fluids

a) Mass

b) Density

c) Specific weight

d) Specific gravity

8. Gives three (3) differences between fluid and gas.


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Specific Volume, Vs

Specific volume of a fluid is defined as the volume of a fluid

occupied by a unit mass or volume per unit mass of a fluid is

called specific volume.

Specific Volume Vs = Volume of fluid/ Mass of FluidOr

Specific Volume Vs = 1/ Density

SI Unit – m3/kg

Vs = 1 / ρ


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Dynamic viscosity (Absolute

Viscosity)

The dynamic viscosity is the ratio of volume to density.

SI Unit – Pascal second @ Ns/m2 @ kg/ms

μ = v / ρ or

Ƭ = μ dc/dy


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Kinematic Viscosity ( nu)

The kinematic viscosity is the ratio of dynamic viscosity to

mass density.

Viscosity of liquids decreases with increase in temperature.

Viscosity of gases increases with increase in temperature.

/secmunits

2

ρ

μ

ν


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Type of Fluids

• Ideal fluid – incompressible and is having noviscosity

• Real Fluid – A fluid without viscosity

•

Newtonian Fluid – the shear stress is directly,proportional to the rate of shear strain

• Non Newtonian Fluids – the shear stress is notproportional to the rate of shear strain

•

Ideal Plastic Fluid – shear stress is more than theyield value and shear stress is proportional to therate of shear strain.


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• Isipadu dan jisim minyak mentah masing-

masing ialah 8.7 m3 dan 7200kg. Nilai

kelikatan dinamik 1.3 x10-3 Ns/m2. Tentukan :

– Ketumpatan bandingan

– Ketumpatan

– Berat tentu

– Kelikatan kinematik


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QUESTION 1

Define each characteristics below including its SI unit:

a. Density ,ρ

b. Specific Weight ,γ

c. Specific Volume ,Vs

QUESTION 2

Fluid with a mass 7500kg filled an open cylinder case with

200cm in diameter and 300 cm height. Calculate :

a. Density ,ρ

b. Specific Weight, c. Specific Volume ,Vs

d. Differential Density @ specific gravity,


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End of Chapter

Topic 1 - Fluid Characteristic

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