FLUID MECHANICS

By

Farhan Ahmad

farhanahmad@uet.edu.pk

Department of Chemical Engineering,

University of Engineering & Technology Lahore

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Course Details

Subject

Subject code

Contact hours

Credit hours

Sessional

Mid term

Final term

Fluid Mechanics

Ch.E - 105

3

3

30 % (Quizzes + Attendance + Class participation + Assignment)

30%

40%

Evaluation procedure

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Introduction to Fluid Mechanics

Importance of Fluid Mechanics in chemical Engineering

Description of fluids

Types of fluids

Classification of fluid flows

Compressible vs Incompressible Fluids

Steady and Unsteady fluid flow

Properties of Fluids

Course Outline (1)

Basic equations of fluid flow

Flow of Incompressible fluids in pipes

Laminar and Turbulent flow in closed channel

Processes of compressible fluids flows

Flow through variable area conduits

Boundary layer concept

Prandtl’s boundary layer equations

Turbulent boundary layers

Dimensional Analysis

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Course Outline (2)

Text Book

Reference

Books

McCabe Warren L., Smith Julian C., Harriott Peter “Unit Operations of Chemical Engineering” 5th Ed. 2001. McGraw Hill Inc.

1. Coulson J.M., Richardson J.F., “Chemical Engineering” Vol-I,

2. Perry Robert H., Green Don W. “Perry’s Chemical Engineering handbook” 7th Ed. 1997. McGraw Hill Inc.

3. “Engineering Fluid Mechanics” by Clayton T. Crowe, Donald F.

Elger, Barbara C. Williams, John A. Roberson., ed. 9.

4. “Fluid Mechanics Fundamentals and Applications” by Yunus A.

Cengel, John M. Cimbala

5. “Fluid Flow for Practicing Chemical Engineer” by J. Patrick

Abulencia, Louis Theodore

Recommended Books

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Text book

“Unit Operations of Chemical Engineering” 5th Ed. By Warren L. McCabe, Julian C. Smith & Peter Harriott

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“Chemical Engineering” volume 1

By J. M. Coulson and J. F. Richardson & with J. R. Backhurst and J. H. Harker

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Perry’s Chemical Engineering Hand book Seventh Edition By Robert H. Perry Don W. Green

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Engineering Fluid Mechanics Ninth Edition

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Fluid Mechanics Fundamentals and Applications By Yunus A. Cengel, John M. Cimbala

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Fluid Flow For the practicing Chemical Engineer By James p. Abulencia, Louis Theodore

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An

Introduction to

Fluid

Mechanics

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What ……..……………………… ???

Why …………………………….. ???

How …………………………….. ???

When ……………………………. ???

Who …........................................ ???

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Chemical Engineering

Unit Operations

Unit Processes

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Chemical Process

Raw materials Products

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Mechanics

Continuum Mechanics

Fluid Mechanics

Fluid Statics

Fluid Kinematics

Fluid Dynamics

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1. Solid

2. Liquid

3. Gas

4. Plasma

State of Matter

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Importance: Applications

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Bio-fluid mechanics

1. Human Body

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Ordinary homes

Water pipelines

Gas pipelines

Sewerage system

air conditioning/heating system

Domestic systems

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Fuel system

Cooling system

Lubricating system

Exhaust system

Automobiles

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Aero planes

Aircrafts

Jet

Missiles

Wind turbines

Aerodynamics

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Water flow through open channels

Environmental Distribution

Hydrology

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Country-wide natural gas transmission system

SNGPL

SSGPL

Industrial Complex piping system

Commercial Applications

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THANKS

The future looks bright !

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doesn’t permanently resist distortion

Fluid is a substance:

Capable of flowing.

Which cannot preserve its shape unless it is restricted into a

particular vessel.

A fluid in equilibrium cannot sustain any shear.

Liquid

Gases

Fluid

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Dimensions and Units

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Standard prefix

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System of Units

SI Units

CGS Units

FPS Engineering Units

Unit conversions

Consistency

Homogeneity

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o Density

o Viscosity

o Kinematic Viscosity

Viscosity of gases

Viscosity of liquids

o Specific Volume

o Specific Gravity

Concepts

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o Fluid Statics

o Hydrostatic equilibrium

o System, Control volume, Control surface

o Pressure

Concepts

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o Uniform vs Non-uniform flow

o Steady vs unsteady flow

o Laminar vs Turbulent flow

o Uni-dimensional vs Multi-dimensional flow

Concepts

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(a) Laminar flow, in which fluid layers move smoothly over one another in the direction of flow, and

(b) Turbulent flow, in which the flow pattern is complex and time-dependent, with considerable motion perpendicular to the principal flow direction.

Laminar vs Turbulent Flow

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o External forces

o Internal forces

o Shear stress

o Velocity Gradient

o Relationship b/w Shear stress and Velocity gradient

Concepts

Viscosity is that property of a fluid due to which it offers resistance to the movement of one layer of fluid over another adjacent layer of fluid.

Viscosity (μ) is the measure of the resisting forces of a fluid which is being deformed.

Viscosity

For gases,

(for air)

0.9 (for carbon dioxide and simple hydrocarbons)

1.1 (for sulfur dioxide and steam)

Viscosity of gases

The viscosity of a gas is almost independent of pressure in the region of pressures where the gas laws apply.

In this region, the viscosity of gases are generally between 0.01 and 0.1 cP.

At high pressures, gas viscosity increases with pressure.

Determine the viscosities of following fluids (at 1 atm);

Air at 180 oF

Air at 30 oC, 100 oC and 200 oC

CO at 0 oC, 300 oC and 600 oC

Helium at 0 oC, 300 oC and 600 oC

F2, Cl2, Br2 and I2 at 20 oC

Methane, Ethane, Propane, n-Butane, n-Pentane and n-Hexane at 20 oC

The viscosities of liquids are generally much greater than those of gases and cover several orders of magnitude.

Liquid viscosities decrease significantly when the temperature is raised.

For example, the viscosity of water falls from 1.79 cP at 0 oC to 0.28 cP at 100 oC.

The viscosity of a liquid increases with pressure, but the effect is generally insignificant at pressures less than 40 atm.

The absolute viscosities of fluids vary over an enormous range of magnitudes, from about 0.1 cP for liquids near their boiling point to as much as 106 P for polymer melts.

Viscosity of Liquids

Determine the viscosities of following fluids (at 1 atm);

Water at 10 oC.

100% Glycerol at 60 oC.

Propyl Alcohol at 30 oC.

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o Types of fluids

o Newtonian fluids

o Non-Newtonian fluids

o Classification of Non-Newtonian fluids

o Time Independent

o Time dependent

o Viscoelastic fluids

Concepts

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Non-Newtonian fluids: Time Independent

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Non-Newtonian fluids: Time Dependent

o Thixotropic

o Rheopectic

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Momentum

Rate of change of momentum

Momentum flux

Momentum balance or Conservation of momentum

Ways of momentum transfer

Concepts