Chapter 1 Fluid Properties2013

8/10/2019 Chapter 1 Fluid Properties2013

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CHE493: FLUID MECHANICS

ATIKAH KADRIOFFICE: PAA1110A

1) Lesson Plan

2) Entrance Survey Form

Course Outcome 1: Identify properties of fluids and various

types of fluid measuring devices.

Course Outcome 2: Develop knowledge on fluids through

friction in pipes, channels and fluid motive

devices.Course Outcome 3: Apply the knowledge in solving fluid

mechanics related problem.


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Applied mechanics concerned with statics and

dynamics of fluids.

Analysis of the behavior of fluids is based on

the fundamental laws of mechanics.


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Chapter 1: FLUID PROPERTIES

Define the nature of a fluid.

Observe fluid mechanics concepts.

Introduce viscosity.

Define appropriate physical properties.

What is fluid?


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FLUID:

Substances in gases or liquid. What these two

has in common? In contrast to solids they are lack the ability to

resist deformation.

SOLID FLUID

Can resist an applied shear by deforming

not continue to move indefinitely.

Deforms continuously under applied shear

it flows under the action of the forces.

Shape changes continuously.

Stress is proportional to strain (independent

of time). The deformation disappear when

the force is removed

Stress is proportional to strain rate. Original

form will not be recovered when the force is

removed

Difference between Solid and Fluid


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SOLID FLUID

Shear stress,


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Properties of Fluids

Intensive properties: independent of the mass

of the system, EgT, P, density.

Extensive properties: depends on the size of

the system, Egtotal mass, total volume,

total momentum.

Specific propertiesextensive properties per

unit mass, Egspecific gravity, specific

weight.


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Units & Dimensions

Unit is a way to assign a number ormeasurement to a dimension.

SI (International system) units

B.G. (British Gravitational system)

Basic dimension used in Fluid Mechanics

Quantity SI unit BG Unit Dimension

Length meter, m foot, ft L

Mass kilogram, kg slug M

Temperature kelvin, K rankine, R

Time second, s second, s T


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Density,

Changes with temperature and pressure,

especially on gases.

Unit

Specific weight,

The force exerted by gravity upon a unit volume of thesubstance.

Unit

water = , air= 12.07


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Ratio of density of a substance to a density of

water at 4o

C. SG of Mercury = 13.6

Unit ?

SG of water? SG of air?

Specific Gravity, SG


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EXAMPLE

A reservoir of glycerin has a mass of 1200 kg

and a volume of 0.952 m3. Determine the

glycerins weight, density and specific gravity.


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Activity


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Viscosity

Viscosity : measurement of fluid resistance towards deformation.: resistance to flow, shearing stress.

: water vs honey

Shear Stress: Tangential force per unit area.


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Two large, parallel plates with a small distance, y apart.

The space between the plates being filled with fluid

Keep upper plate moving at constant velocity, u by applying

a constant force, F tangential to the area of the plate. Thus there must be a viscous interaction between plate and

fluid.

Fluid in contact with upper plate will adhere to it and willmove at velocity, u.

Fluid in contact with the fixed plate will have velocity = 0 If y and u are not too great, velocity profile will be a

straight line (laminar flow).

From experiment , Shear Force, F :

Varies with area of the plate

Varies with velocity, u

Varies Inversely with distance, y


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(Newtons Law of Viscosity)


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Chapter 1 Fluid Properties2013

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