Ebook. Fluid Mechanics By Yunus A. Cengel, John M. Cimbala.docx

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CONTENTS Preface xv

Application Spotlight: What Nuclear Blasts and Raindrops Have in Common 31 Summary 30 References and Suggested Reading 30 Problems 32

CHAPTER O NE INTRODUCTION AND BASIC CONCEPTS 1–1 1–2 1–3 1–4

1

Introduction 2

C H A P T E R T WO

What Is a Fluid? 2 Application Areas of Fluid Mechanics 4

PROPERTIES OF FLUIDS 35

The No-Slip Condition 6 A Brief History of Fluid Mechanics Classification of Fluid Flows 9

2–1 7

Continuum 36

2–2

Viscous versus Inviscid Regions of Flow 9 Internal versus External Flow 10 Compressible versus Incompressible Flow 10 Laminar versus Turbulent Flow 11 Natural (or Unforced) versus Forced Flow 11 Steady versus Unsteady Flow 11 One-, Two-, and Three-Dimensional Flows 12

1–5 1–6

System and Control Volume 14 Importance of Dimensions and Units

2–3 2–4 2–5 2–6 2–7

15

Step Step Step Step Step Step Step

1–9

1: 2: 3: 4: 5: 6: 7:

Vapor Pressure and Cavitation 39 Energy and Specific Heats 41 Coefficient of Compressibility 42 Viscosity 46 Surface Tension and Capillary Effect

51

Capillary Effect 53 Summary 55 References and Suggested Reading 56

Mathematical Modeling of Engineering Problems 21 Problem-Solving Technique

37

Coefficient of Volume Expansion 44

Application Spotlight: Cavitation

57

Problems 58

Modeling in Engineering 21

1–8

Density and Specific Gravity Density of Ideal Gases 38

Some SI and English Units 16 Dimensional Homogeneity 18 Unity Conversion Ratios 20

1–7

Introduction 36

22

CHAPTER THREE

Problem Statement 22 Schematic 23 Assumptions and Approximations 23 Physical Laws 23 Properties 23 Calculations 23 Reasoning, Verification, and Discussion 23

Engineering Software Packages

PRESSURE AND FLUID STATICS 65 3–1

Pressure at a Point 67 Variation of Pressure with Depth 68

24

3–2

Engineering Equation Solver (EES) 25 FLUENT 26

1–10 Accuracy, Precision, and Significant Digits

Pressure 66

The Manometer 71 Other Pressure Measurement Devices 74

26

3–3 3–4

The Barometer and Atmospheric Pressure Introduction to Fluid Statics 78

75

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3–5

Hydrostatic Forces on Submerged Plane Surfaces 79

C H A P T E R F I VE MASS, BERNOULLI, AND ENERGY EQUATIONS 171

Special Case: Submerged Rectangular Plate 82

3–6

Hydrostatic Forces on Submerged Curved Surfaces 85

3–7

Buoyancy and Stability

Stability of Immersed and Floating Bodies

3–8

5–1

89

Fluids in Rigid-Body Motion

Conservation of Mass 172 Conservation of Momentum 172 Conservation of Energy 172

92

95

5–2

Special Case 1: Fluids at Rest 96 Special Case 2: Free Fall of a Fluid Body Acceleration on a Straight Path 97 Rotation in a Cylindrical Container 99

97

5–3 5–4

FLUID KINEMATICS 121 Lagrangian and Eulerian Descriptions

122

Acceleration Field 124 Material Derivative 127

Fundamentals of Flow Visualization

5–5 5–6

129

Streamlines and Streamtubes 129 Pathlines 130 Streaklines 132 Timelines 134 Refractive Flow Visualization Techniques 135 Surface Flow Visualization Techniques 136

4–3

Plots of Fluid Flow Data

5–7

139

The Reynolds Transport Theorem

148

Alternate Derivation of the Reynolds Transport Theorem 153 Relationship between Material Derivative and RTT 155

Application Spotlight: Fluidic Actuators Summary 156 References and Suggested Reading 158 Problems 158

Applications of the Bernoulli Equation General Energy Equation 201

194

Energy Analysis of Steady Flows

206

Summary 215 References and Suggested Reading 216 Problems 216

Types of Motion or Deformation of Fluid Elements 139 Vorticity and Rotationality 144 Comparison of Two Circular Flows 147

4–5

180

Special Case: Incompressible Flow with No Mechanical Work Devices and Negligible Friction 208 Kinetic Energy Correction Factor, a 208

136

Other Kinematic Descriptions

Mechanical Energy and Efficiency The Bernoulli Equation 185

Energy Transfer by Heat, Q 202 Energy Transfer by Work, W 202

Profile Plots 137 Vector Plots 137 Contour Plots 138

4–4

173

Acceleration of a Fluid Particle 186 Derivation of the Bernoulli Equation 186 Force Balance across Streamlines 188 Unsteady, Compressible Flow 189 Static, Dynamic, and Stagnation Pressures 189 Limitations on the Use of the Bernoulli Equation 190 Hydraulic Grade Line (HGL) and Energy Grade Line (EGL) 192

C H A P T E R F O UR

4–2

Conservation of Mass

Mass and Volume Flow Rates 173 Conservation of Mass Principle 175 Moving or Deforming Control Volumes 177 Mass Balance for Steady-Flow Processes 177 Special Case: Incompressible Flow 178

Summary 102 References and Suggested Reading 103 Problems 103

4–1

Introduction 172

CHAPTER S I X MOMENTUM ANALYSIS OF FLOW SYSTEMS 227 6–1

157

6–2 6–3

Newton’s Laws and Conservation of Momentum 228 Choosing a Control Volume 229 Forces Acting on a Control Volume

230

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xii FLUID MECHANICS

6–4

The Linear Momentum Equation

8–3

233

Special Cases 235 Momentum-Flux Correction Factor, b 235 Steady Flow 238 Steady Flow with One Inlet and One Outlet 238 Flow with No External Forces 238

6–5 6–6

8–4

Review of Rotational Motion and Angular Momentum 248 The Angular Momentum Equation 250

8–5

8–6 8–7

DIMENSIONAL ANALYSIS AND MODELING

269

Nondimensionalization of Equations 272

Dimensional Analysis and Similarity 277 The Method of Repeating Variables and the Buckingham Pi Theorem 281 Historical Spotlight: Persons Honored by Nondimensional Parameters 289 Experimental Testing and Incomplete Similarity 297 Setup of an Experiment and Correlation of Experimental Data 297 Incomplete Similarity 298 Wind Tunnel Testing 298 Flows with Free Surfaces 301

Reynolds Number 324

354

304

Flow Rate and Velocity Measurement

364

Summary 384 References and Suggested Reading 385 Problems 386

C H A P T E R N I NE DIFFERENTIAL ANALYSIS OF FLUID FLOW 399 9–1 9–2

Introduction 400 Conservation of Mass—The Continuity Equation 400 Derivation Using the Divergence Theorem 401 Derivation Using an Infinitesimal Control Volume 402 Alternative Form of the Continuity Equation 405 Continuity Equation in Cylindrical Coordinates 406 Special Cases of the Continuity Equation 406

FLOW IN PIPES 321 Introduction 322 Laminar and Turbulent Flows

Minor Losses 347 Piping Networks and Pump Selection

Application Spotlight: How Orifice Plate Flowmeters Work, or Do Not Work 383

CHAPTER EIGHT 8–1 8–2

335

Pitot and Pitot-Static Probes 365 Obstruction Flowmeters: Orifice, Venturi, and Nozzle Meters 366 Positive Displacement Flowmeters 369 Turbine Flowmeters 370 Variable-Area Flowmeters (Rotameters) 372 Ultrasonic Flowmeters 373 Electromagnetic Flowmeters 375 Vortex Flowmeters 376 Thermal (Hot-Wire and Hot-Film) Anemometers 377 Laser Doppler Velocimetry 378 Particle Image Velocimetry 380

Dimensions and Units 270 Dimensional Homogeneity 271

Summary 305 References and Suggested Reading 305 Problems 305

Turbulent Flow in Pipes

Piping Systems with Pumps and Turbines 356

CHAPTER SEVEN

Application Spotlight: How a Fly Flies

327

Turbulent Shear Stress 336 Turbulent Velocity Profile 338 The Moody Chart 340 Types of Fluid Flow Problems 343

8–8

7–5

Laminar Flow in Pipes

Pressure Drop and Head Loss 329 Inclined Pipes 331 Laminar Flow in Noncircular Pipes 332

Summary 259 References and Suggested Reading 259 Problems 260

7–3 7–4

325

Entry Lengths 326

Special Cases 252 Flow with No External Moments 253 Radial-Flow Devices 254

7–1 7–2

The Entrance Region

9–3 323

The Stream Function

412

The Stream Function in Cartesian Coordinates 412 The Stream Function in Cylindrical Coordinates 419 The Compressible Stream Function 420

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9–4

Conservation of Linear Momentum—Cauchy’s Equation 421 Derivation Using the Divergence Theorem 421 Derivation Using an Infinitesimal Control Volume 422 Alternative Form of Cauchy’s Equation 425 Derivation Using Newton’s Second Law 425

9–5

The Navier–Stokes Equation

426

Introduction 426 Newtonian versus Non-Newtonian Fluids 427 Derivation of the Navier–Stokes Equation for Incompressible, Isothermal Flow 428 Continuity and Navier–Stokes Equations in Cartesian Coordinates 430 Continuity and Navier–Stokes Equations in Cylindrical Coordinates 431

9–6

Differential Analysis of Fluid Flow Problems 432

10–6 The Boundary Layer Approximation

510

The Boundary Layer Equations 515 The Boundary Layer Procedure 520 Displacement Thickness 524 Momentum Thickness 527 Turbulent Flat Plate Boundary Layer 528 Boundary Layers with Pressure Gradients 534 The Momentum Integral Technique for Boundary Layers 539

Application Spotlight: Droplet Formation

549

Summary 547 References and Suggested Reading 548 Problems 550

CHAPTER ELEVEN FLOW OVER BODIES: DRAG AND LIFT 561

Calculation of the Pressure Field for a Known Velocity Field 432 Exact Solutions of the Continuity and Navier–Stokes Equations 437 Summary 455 References and Suggested Reading 456 Problems 456

11–1 Introduction 562 11–2 Drag and Lift 563 11–3 Friction and Pressure Drag 567 Reducing Drag by Streamlining 568 Flow Separation 569

11–4 Drag Coefficients of Common Geometries Biological Systems and Drag 572 Drag Coefficients of Vehicles 574 Superposition 577

CHAPTER T E N APPROXIMATE SOLUTIONS OF THE NAVIER–STOKES EQUATION 471 10–1 Introduction 472 10–2 Nondimensionalized Equations of Motion 473 10–3 The Creeping Flow Approximation

11–5 Parallel Flow over Flat Plates

579

Friction Coefficient 580

11–6 Flow over Cylinders and Spheres

583

Effect of Surface Roughness 586

476

Drag on a Sphere in Creeping Flow 479

10–4 Approximation for Inviscid Regions of Flow 481

11–7 Lift 587 End Effects of Wing Tips 591 Lift Generated by Spinning 594

Application Spotlight: Drag Reduction

600

Summary 598 References and Suggested Reading 599 Problems 601

Derivation of the Bernoulli Equation in Inviscid Regions of Flow 482

10–5 The Irrotational Flow Approximation

571

485

Continuity Equation 485 Momentum Equation 487 Derivation of the Bernoulli Equation in Irrotational Regions of Flow 487 Two-Dimensional Irrotational Regions of Flow 490 Superposition in Irrotational Regions of Flow 494 Elementary Planar Irrotational Flows 494 Irrotational Flows Formed by Superposition 501

C H A P T E R T W ELVE COMPRESSIBLE FLOW 611 12–1 Stagnation Properties 612 12–2 Speed of Sound and Mach Number 615 12–3 One-Dimensional Isentropic Flow 617 Variation of Fluid Velocity with Flow Area 620 Property Relations for Isentropic Flow of Ideal Gases 622

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xiv FLUID MECHANICS

12–4 Isentropic Flow through Nozzles

Summary 723 References and Suggested Reading 724 Problems 725

624

Converging Nozzles 625 Converging–Diverging Nozzles 629

12–5 Shock Waves and Expansion Waves

633

CHAPTER FOURTEEN

Normal Shocks 633 Oblique Shocks 640 Prandtl–Meyer Expansion Waves 644

TURBOMACHINERY

12–6 Duct Flow with Heat Transfer and Negligible Friction (Rayleigh Flow) 648

14–1 Classifications and Terminology 14–2 Pumps 738

Property Relations for Rayleigh Flow 654 Choked Rayleigh Flow 655

Property Relations for Fanno Flow 660 Choked Fanno Flow 663

Application Spotlight: Shock-Wave/ Boundary-Layer Interactions 667

14–3 Pump Scaling Laws 773

Summary 668 References and Suggested Reading 669 Problems 669

Dimensional Analysis 773 Pump Specific Speed 775 Affinity Laws 777

14–4 Turbines

CHAPTER THIRTEEN 13–1 Classification of Open-Channel Flows

680

Uniform and Varied Flows 680 Laminar and Turbulent Flows in Channels 681

683

Application Spotlight: Rotary Fuel Atomizers 802 Summary 803 References and Suggested Reading 803 Problems 804

690

Critical Uniform Flow 693 Superposition Method for Nonuniform Perimeters

693

APPENDIX

697

Rectangular Channels 699 Trapezoidal Channels 699

Liquid Surface Profiles in Open Channels, y (x) Some Representative Surface Profiles 706 Numerical Solution of Surface Profile 708

1

PROPERTY TABLES AND CHARTS (SI UNITS) 817

13–7 Gradually Varied Flow 701 703

13–8 Rapidly Varied Flow and Hydraulic Jump 13–9 Flow Control and Measurement 714 Underflow Gates 714 Overflow Gates 716

14–5 Turbine Scaling Laws 795 Dimensionless Turbine Parameters 795 Turbine Specific Speed 797 Gas and Steam Turbines 800

Speed of Surface Waves 685

13–6 Best Hydraulic Cross Sections

781

Positive-Displacement Turbines 782 Dynamic Turbines 782 Impulse Turbines 783 Reaction Turbines 785

OPEN-CHANNEL FLOW 679

13–3 Specific Energy 687 13–4 Continuity and Energy Equations 13–5 Uniform Flow in Channels 691

736

Pump Performance Curves and Matching a Pump to a Piping System 739 Pump Cavitation and Net Positive Suction Head 745 Pumps in Series and Parallel 748 Positive-Displacement Pumps 751 Dynamic Pumps 754 Centrifugal Pumps 754 Axial Pumps 764

12–7 Adiabatic Duct Flow with Friction (Fanno Flow) 657

13–2 Froude Number and Wave Speed

735

TABLE A–1 709

TABLE A–2 TABLE A–3

Molar Mass, Gas Constant, and Ideal-Gas Specfic Heats of Some Substances 818 Boiling and Freezing Point Properties 819 Properties of Saturated Water 820