fluid mechanics lecture notes 2012

8/12/2019 Fluid Mechanics Lecture Notes 2012

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FLUID

MECHANICS

Manila Review Institute

Chemical Engineering Reviewfor the November, 2012 Board Examination

[email protected] CP No. 09185663419

Dr. Servillano Olao, Jr.

Join the yahoo groups: mrii_che_2012

Group homepage: http://groups.yahoo.com/group/mrii_che_2012

Group email: [email protected]


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Nature of Fluids

A fluid is a substance that does notpermanently resist distortion.

Some physical properties of fluids:a) Density or relative density

b) Viscosityc) Surface tension

6/18/2012 3S. Olano, Jr. MRII

Fluid Mechanics


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Types of Fluids

1. Incompressible

Density is not affected by changes intemperature and pressure

2. Compressible

Density varies appreciably withtemperature and pressure

Pressure Concept

For a static fluid, the pressure at any pointis independent of direction.


Fluid Mechanics


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English SI

Length, L ft., inch meter (m)Mass, M lbm, slugs Kg

Time, T seconds (s), hr s

Force, F lbf newton (N)Density, lbm/ft

3, slug/ft3 Kg/m3

Systems of Units

Relationship between Force and Mass: F=ma

2

2

32.16ENGLISH:32.16c

ftg lbf sF m lbm lbm lbf

lbm ftg lbm

lbf s

= = =

2 2SI: 9.806 ( )m mF mg kg kg newton N

s s

= = = 6/18/2012 5S. Olano, Jr. MRII

Fluid Mechanics


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A. Fluid Statics and Applications

Hydrostatic Equilibrium

Force balance:

- ( ) - 0

0

c

c

g

p S p dp S Sdz g

gdp dz

g

+ =

+ =



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Fluid Statics and Applications

2 11 2

constant

( )

c

c

p gz

gp p g

z zg

+ =

=

Hydrostatic Equilibrium,

for constant density (most liquids)

0

0

c

c

pM gdp dzRT g

dp gM dz

p g RT

+ =

+ =

Barometric EquationFor an ideal gas, = (pM/RT).

Substituting,



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Integrating between levels 1 and 2:

( )

( )

22 1

1

2 12

1

ln

exp

c

c

p gMz z

p g R T

gM z zpp g R T

=

=

(Called the barometric equation)




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2. Simple Manometers

Pressure balance at level 0:

z

g

gH

g

gpp

g

gH

g

ga

g

gzp

g

ga

g

gHp

c

mm

c

c

mm

cccc

m

+=

+++=++

)(21

21

Simplifying gives:




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Viscous forces in a fluid

Rheological Properties of Fluids



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B. Fluid Dynamics (Flow of Fluids)


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Evaluation of Fanning friction factor

Fluid Dynamics and Applications



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Evaluation of surface roughness factor



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Flow of Incompressible Fluids

3. Turbulent flow in pipes and closed channels(correlation equations forf )


Blassius Formula: (for smooth tubes)

Colebrook Equation:

Churchill Equation:


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Non-Circular Pipes


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Friction due to Pipe Fittings


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Evaluation of Ff (for fittings and valves)



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Entrance and Exit Effects in a Pipe

Entrance Effects for fully developed velocity profile:

for laminar flow:

for turbulent flow:

Le


Exit Effects:


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Coverage Chart



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Classification of Pumps



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Examples of Pumps

A. Centrifugal pumps

Dynamic pumps

B. Reciprocal pumps

Positive displacement pumpsC. Gear pumps

D. Axial flow pumps



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Examples of Pumps


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Examples of Pumps



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Examples of Pumps


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Examples of Pumps



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Guide in the selection of Pumps



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System head vs Available head



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==== 1HH mmv



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Pitot Tube



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Pitot Tube

For Compressible Fluids:



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Flow Metersc) Head Meters (Orifices, venturi meters,

nozzles)



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Evaluation of C (discharge coefficient)

Types of Taps:



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Friction Loss Due to Flowmeters


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Flow in Open Channels and Weirs

1. Rectangular Weir

(Modified Francis Weir Formula)

)2)(2.0(415.05.1

ghhLq oo=



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====

tan

g2h31.0q

5.2

o

2. Triangular Weir Notch

Note: Both equations apply only for water



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fluid mechanics lecture notes 2012

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