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FLUENT 6.2 Tutorial Guide

January 2005

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Copyright c 2005 by Fluent Inc.All rights reserved. No part of this document may be reproduced or otherwise used in

any form without express written permission from Fluent Inc.

Airpak, FIDAP, FLUENT, FloWizard, GAMBIT, Icemax, Icepak, Icepro, MixSim, and

POLYFLOW are registered trademarks of Fluent Inc. All other products or namebrands are trademarks of their respective holders.

CHEMKIN is a registered trademark of Reaction Design Inc.

Portions of this program include material copyrighted by PathScale Corporation2003-2004.

Fluent Inc.Centerra Resource Park

10 Cavendish CourtLebanon, NH 03766

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Volume 1

1 Introduction to Using FLUENT: Fluid Flow and Heat Transfer in a Mixing Elbow2 Modeling Periodic Flow and Heat Transfer3 Modeling External Compressible Flow4 Modeling Unsteady Compressible Flow

5 Modeling Radiation and Natural Convection6 Using a Non-Conformal Mesh7 Using a Single Rotating Reference Frame8 Using Multiple Rotating Reference Frames9 Using the Mixing Plane Model10 Using Sliding Meshes11 Using Dynamic Meshes

Volume 2

12 Modeling Species Transport and Gaseous Combustion13 Using the Non-Premixed Combustion Model

14 Modeling Surface Chemistry15 Modeling Evaporating Liquid Spray16 Using the VOF Model17 Modeling Cavitation18 Using the Mixture and Eulerian Multiphase Models19 Using the Eulerian Multiphase Model for Granular Flow20 Modeling Solidication21 Using the Eulerian Granular Multiphase Model with Heat Transfer22 Postprocessing23 Turbo Postprocessing24 Parallel Processing

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Using This Manual

Whats In This Manual

The FLUENT Tutorial Guide contains a number of tutorials that teach you how to useFLUENTto solve different types of problems. In each tutorial, features related to problemsetup and postprocessing are demonstrated.

Tutorial 1 is a detailed tutorial designed to introduce the beginner to FLUENT. Thistutorial provides explicit instructions for all steps in the problem setup, solution, andpostprocessing. The remaining tutorials assume that you have read or solved Tutorial 1,or that you are already familiar with FLUENTand its interface. In these tutorials, some

steps will not be shown explicitly.All of the tutorials include some postprocessing instructions, but Tutorial 22 is devotedentirely to standard postprocessing, and Tutorial 23 is devoted to turbomachinery-specicpostprocessing.

Where to Find the Files Used in the Tutorials

Each of the tutorials uses an existing mesh le. (Tutorials for mesh generation areprovided with the mesh generator documentation.) You will nd the appropriate meshle (and any other relevant les used in the tutorial) on the FLUENTdocumentation CD.The Preparation step of each tutorial will tell you where to nd the necessary les.(Note that Tutorials 22, 23, and 24 use existing case and data les.)

Some of the more complex tutorials may require a signicant amount of computationaltime. If you want to look at the results immediately, without waiting for the calcula-tion to nish, you can nd the case and data les associated with the tutorial on thedocumentation CD (in the same directory where you found the mesh le).

How To Use This Manual

Depending on your familiarity with computational uid dynamics and Fluent Inc. soft-ware, you can use this tutorial guide in a variety of ways.

For the Beginner

If you are a beginning user of FLUENTyou should rst read and solve Tutorial 1, in orderto familiarize yourself with the interface and with basic setup and solution procedures.

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Using This Manual

You may then want to try a tutorial that demonstrates features that you are going touse in your application. For example, if you are planning to solve a problem using thenon-premixed combustion model, you should look at Tutorial 13.

You may want to refer to other tutorials for instructions on using specic features, suchas custom eld functions, grid scaling, and so on, even if the problem solved in the

tutorial is not of particular interest to you. To learn about postprocessing, you can lookat Tutorial 22, which is devoted entirely to postprocessing (although the other tutorialsall contain some postprocessing as well). For turbomachinery-specic postprocessing, seeTutorial 23.

For the Experienced User

If you are an experienced FLUENT user, you can read and/or solve the tutorial(s) thatdemonstrate features that you are going to use in your application. For example, if youare planning to solve a problem using the non-premixed combustion model, you shouldlook at Tutorial 13.

You may want to refer to other tutorials for instructions on using specic features, suchas custom eld functions, grid scaling, and so on, even if the problem solved in thetutorial is not of particular interest to you. To learn about postprocessing, you can lookat Tutorial 22, which is devoted entirely to postprocessing (although the other tutorialsall contain some postprocessing as well). For turbomachinery-specic postprocessing, seeTutorial 23.

Typographical Conventions Used In This Manual

Several typographical conventions are used in the text of the tutorials to facilitate yourlearning process.

An informational icon (i ) marks an important note.

An warning icon ( ! ) marks a warning. Different type styles are used to indicate graphical user interface menu items andtext interface menu items (e.g., Zone Surface panel, surface/zone-surface com-

mand).

The text interface type style is also used when illustrating exactly what appears onthe screen or exactly what you must type in the text window or in a panel. Instructions for performing each step in a tutorial will appear in standard type.Additional information about a step in a tutorial appears in italicized type.

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A mini ow chart is used to indicate the menu selections that lead you to a speciccommand or panel. For example,Dene Boundary Conditions...

indicates that the Boundary Conditions... menu item can be selected from the Denepull-down menu.

The words surrounded by boxes invoke menus (or submenus) and the arrows pointfrom a specic menu toward the item you should select from that menu.

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Contents

1 Introduction to Using FLUENT: Fluid Flow and Heat Transferin a Mixing Elbow 1-1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1

Prerequisites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1

Problem Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2

Setup and Solution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3

Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3Step 1: Grid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4

Step 2: Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-9

Step 3: Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-11

Step 4: Boundary Conditions . . . . . . . . . . . . . . . . . . . . . . . . 1-13

Step 5: Solution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-18

Step 6: Displaying the Preliminary Solution . . . . . . . . . . . . . . . . 1-25

Step 7: Enabling Second-Order Discretization . . . . . . . . . . . . . . . 1-38Step 8: Adapting the Grid . . . . . . . . . . . . . . . . . . . . . . . . . . 1-43

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-52

2 Modeling Periodic Flow and Heat Transfer 2-1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

Prerequisites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1



Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3

Step 1: Grid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3

Step 2: Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-6

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Step 3: Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-8


Step 5: Solution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-13

Step 6: Postprocessing . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-16

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-26

3 Modeling External Compressible Flow 3-1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

Prerequisites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1



Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2Step 1: Grid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3

Step 2: Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6

Step 3: Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-8

Step 4: Operating Conditions . . . . . . . . . . . . . . . . . . . . . . . . 3-10


Step 6: Solution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-12

Step 7: Postprocessing . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-24Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-29

4 Modeling Unsteady Compressible Flow 4-1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1

Prerequisites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1



Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2

Step 1: Grid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3

Step 2: Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5

Step 3: Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-6

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Step 4: Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-8



Step 7: Solution: Steady Flow . . . . . . . . . . . . . . . . . . . . . . . . 4-12

Step 8: Enable Time Dependence and Set Unsteady Conditions . . . . . 4-24

Step 9: Solution: Unsteady Flow . . . . . . . . . . . . . . . . . . . . . . 4-27

Step 10: Saving and Postprocessing Time-Dependent Data Sets . . . . . 4-30

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-43

5 Modeling Radiation and Natural Convection 5-1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1

Prerequisites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1Problem Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1


Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-2

Step 1: Grid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3

Step 2: Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-6

Step 3: Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-9

Step 4: Boundary Conditions . . . . . . . . . . . . . . . . . . . . . . . . 5-11Step 5: Solution for the Rosseland Model . . . . . . . . . . . . . . . . . . 5-13

Step 6: Postprocessing for the Rosseland Model . . . . . . . . . . . . . . 5-16

Step 7: P-1 Model Denition, Solution, and Postprocessing . . . . . . . . 5-25

Step 8: DTRM Denition, Solution, and Postprocessing . . . . . . . . . . 5-29

Step 9: DO Model Denition, Solution, and Postprocessing . . . . . . . . 5-33

Step 10: Comparison of y-Velocity Plots . . . . . . . . . . . . . . . . . . 5-36

Step 11: Comparison of Radiation Models for an OpticallyThick Medium . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-38

Step 12: S2S Model Denition, Solution and Postprocessing for aNon-Participating Medium . . . . . . . . . . . . . . . . . . . . . 5-40

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Step 13: Comparison of Radiation Models for a Non-ParticipatingMedium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-45

Step 14: S2S Model Denition, Solution and Postprocessing withPartial Enclosure . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-47

Step 15: Comparison of S2S Models with and without Partial Enclosure . 5-52

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-53

6 Using a Non-Conformal Mesh 6-1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1

Prerequisites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1



Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-3Step 1: Merging the Mesh Files . . . . . . . . . . . . . . . . . . . . . . . 6-4

Step 2: Grid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-5

Step 3: Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-8

Step 4: Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-10



Step 7: Grid Interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-20Step 8: Solution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-21


Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-31

7 Using a Single Rotating Reference Frame 7-1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-1

Prerequisites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-1



Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-3

Step 1: Grid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-3

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Step 2: Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-5

Step 3: Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-6

Step 4: Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-8


Step 6: Solution Using the Standard k- Model . . . . . . . . . . . . . . 7-12

Step 7: Postprocessing for the Standard k- Solution . . . . . . . . . . . 7-18

Step 8: Solution Using the RNG k- Model . . . . . . . . . . . . . . . . . 7-24

Step 9: Postprocessing for the RNG k- Solution . . . . . . . . . . . . . . 7-26

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-29

Further Improvements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-30

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-30

8 Using Multiple Rotating Reference Frames 8-1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-1

Prerequisites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-1



Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-3

Step 1: Grid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-3Step 2: Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-6

Step 3: Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-8


Step 5: Solution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-15


Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-22

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9 Using the Mixing Plane Model 9-1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-1

Prerequisites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-1



Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-2

Step 1: Grid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-3

Step 2: Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-5

Step 3: Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-6

Step 4: Mixing Plane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-8

Step 5: Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-10


Step 7: Solution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-21


Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-33

10 Using Sliding Meshes 10-1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-1



Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-3

Step 1: Merging the Mesh Files . . . . . . . . . . . . . . . . . . . . . . . 10-4

Step 2: Grid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-5

Step 3: Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-8

Step 4: Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-10



Step 7: Grid Interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-18

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Step 8: Solution: Steady Flow with Non-Moving Rotor . . . . . . . . . . 10-19

Step 9: Enable Time Dependence and Sliding Rotor Motion . . . . . . . 10-30

Step 10: Solution: Unsteady Flow with Moving Rotor . . . . . . . . . . . 10-33

Step 11: Postprocessing at t = 0.1 Second . . . . . . . . . . . . . . . . . 10-41

Step 12: Saving and Postprocessing Time-Dependent Data Sets . . . . . 10-45

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-49

11 Using Dynamic Meshes 11-1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-1

Prerequisites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-1


Setup and Solution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-2Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-2

Step 1: Grid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-3

Step 2: Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-5

Step 3: Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-6

Step 4: Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-8


Step 6: Boundary Conditions . . . . . . . . . . . . . . . . . . . . . . . . 11-10Step 7: Grid Interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-12

Step 8: Mesh Motion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-13

Step 9: Solution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-20

Step 10: Postprocessing . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-28

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-30

12 Modeling Species Transport and Gaseous Combustion 12-1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-1

Prerequisites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-1


Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-3

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Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-3

Step 1: Grid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-4

Step 2: Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-6

Step 3: Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-10


Step 5: Initial Solution Using Constant Heat Capacity . . . . . . . . . . 12-20

Step 6: Solution Using Non-Constant Heat Capacity . . . . . . . . . . . 12-25


Step 8: NOx Prediction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-38

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-47

Further Improvements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-47

13 Using the Non-Premixed Combustion Model 13-1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-1

Prerequisites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-1



Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-3Step 1: Grid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-3

Step 2: Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-5

Step 3: Non Adiabatic PDF Table . . . . . . . . . . . . . . . . . . . . . . 13-8

Step 4: Models: Discrete Phase . . . . . . . . . . . . . . . . . . . . . . . 13-16

Step 5: Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-22



Step 8: Solution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-31


Step 10: Energy Balances and Particle Reporting . . . . . . . . . . . . . 13-41

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CONTENTS

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-44

Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-45

Coal Analysis for Elemental Composition . . . . . . . . . . . . . . . . . . 13-45

Discrete Phase Material Properties . . . . . . . . . . . . . . . . . . . . . 13-46

14 Modeling Surface Chemistry 14-1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14-1

Prerequisites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14-1



Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14-3


Step 3: Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14-10



Step 6: Solution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14-23


Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14-32

15 Modeling Evaporating Liquid Spray 15-1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-1

Prerequisites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-1



Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-2

Step 1: Grid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-3

Step 2: Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-8


Step 4: Initial Solution Without Droplets . . . . . . . . . . . . . . . . . . 15-16

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Step 5: Create a Spray Injection . . . . . . . . . . . . . . . . . . . . . . . 15-24

Step 6: Solution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-30


Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-37

16 Using the VOF Model 16-1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-1

Prerequisites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-1



Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-2


Step 3: Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-8

Step 4: Phases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-9



Step 7: Solution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-16

Step 8: Postprocessing . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-31Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-41

17 Modeling Cavitation 17-1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-1

Prerequisites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-1



Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-2

Step 1: Grid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-3

Step 2: Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-5

Step 3: Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-9

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Step 4: Phases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-11



Step 7: Solution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-17


Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-24

18 Using the Mixture and Eulerian Multiphase Models 18-1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-1

Prerequisites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-1


Setup and Solution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-2Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-2

Step 1: Grid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-3

Step 2: Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-5

Step 3: Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-9

Step 4: Phases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-10


Step 6: Solution Using the Mixture Model . . . . . . . . . . . . . . . . . 18-18Step 7: Postprocessing for the Mixture Solution . . . . . . . . . . . . . . 18-20

Step 8: Setup and Solution for the Eulerian Model . . . . . . . . . . . . . 18-24

Step 9: Postprocessing for the Eulerian Model . . . . . . . . . . . . . . . 18-28

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-30

19 Using the Eulerian Multiphase Model for Granular Flow 19-1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19-1

Prerequisites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19-1



Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19-2

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CONTENTS

Step 1: Grid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19-3

Step 2: Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19-7

Step 3: Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19-10

Step 4: Phases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19-12


Step 6: Solution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19-19


Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19-33

20 Modeling Solidication 20-1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20-1



Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20-3

Step 1: Grid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20-3

Step 2: Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20-5

Step 3: Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20-8

Step 4: Boundary Conditions . . . . . . . . . . . . . . . . . . . . . . . . 20-10Step 5: Solution: Steady Conduction . . . . . . . . . . . . . . . . . . . . 20-16

Step 6: Solution: Unsteady Flow and Heat Transfer . . . . . . . . . . . . 20-23

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20-31

21 Using the Eulerian Granular Multiphase Model with Heat Transfer 21-1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21-1

Prerequisites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21-1



Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21-2

Step 1: Grid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21-3

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Step 2: Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21-5

Step 3: Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21-8

Step 4: Phases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21-11


Step 6: Solution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21-21


Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21-32

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21-32

22 Postprocessing 22-1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22-1



Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22-2

Step 1: Grid Display . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22-3

Step 2: Adding Lights . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22-5

Step 3: Creating Isosurfaces . . . . . . . . . . . . . . . . . . . . . . . . . 22-9

Step 4: Contours . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22-10Step 5: Velocity Vectors . . . . . . . . . . . . . . . . . . . . . . . . . . . 22-13

Step 6: Animation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22-18

Step 7: Pathlines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22-22

Step 8: Overlaying Velocity Vectors on the Pathline Display . . . . . . . 22-28

Step 9: Exploded Views . . . . . . . . . . . . . . . . . . . . . . . . . . . 22-31

Step 10: Animating the Display of Results in SuccessiveStreamwise Planes . . . . . . . . . . . . . . . . . . . . . . . . . . 22-36

Step 11: XY Plots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22-38

Step 12: Annotation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22-42

Step 13: Saving Hardcopy Files . . . . . . . . . . . . . . . . . . . . . . . 22-44

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22-44

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23 Turbo Postprocessing 23-1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23-1

Prerequisites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23-1



Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23-2

Step 1: Reading the Case and Data Files . . . . . . . . . . . . . . . . . . 23-2

Step 2: Grid Display . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23-3

Step 3: Dening the Turbomachinery Topology . . . . . . . . . . . . . . 23-5

Step 4: Isosurface Creation . . . . . . . . . . . . . . . . . . . . . . . . . . 23-7

Step 5: Contours . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23-9

Step 6: Reporting Turbo Quantities . . . . . . . . . . . . . . . . . . . . . 23-14

Step 7: Averaged Contours . . . . . . . . . . . . . . . . . . . . . . . . . . 23-15

Step 8: 2D Contours . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23-17

Step 9: Averaged XY Plots . . . . . . . . . . . . . . . . . . . . . . . . . 23-19

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23-21

24 Parallel Processing 24-1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24-1Prerequisites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24-1



Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24-3

Step 1: Starting the Parallel Version of FLUENT . . . . . . . . . . . . . . 24-3

Step 1A: Multiprocessor UNIX Machine . . . . . . . . . . . . . . . . . . 24-4

Step 1B: Multiprocessor Windows Machine . . . . . . . . . . . . . . . . . 24-6

Step 1C: Network of UNIX Workstations . . . . . . . . . . . . . . . . . . 24-7

Step 1D: Network of Windows Workstations . . . . . . . . . . . . . . . . 24-11

Step 2: Reading and Partitioning the Grid . . . . . . . . . . . . . . . . . 24-12

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Step 3: Solution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24-18

Step 4: Checking Parallel Performance . . . . . . . . . . . . . . . . . . . 24-19


Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24-23

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Tutorial 1. Introduction to UsingFLUENT : Fluid Flow andHeat Transfer in a Mixing Elbow

Introduction

This tutorial illustrates the setup and solution of the two-dimensional turbulent uid owand heat transfer in a mixing junction. The mixing elbow conguration is encounteredin piping systems in power plants and process industries. It is often important to predictthe ow eld and temperature eld in the neighborhood of the mixing region in order toproperly design the location of inlet pipes.

In this tutorial you will learn how to:

Read an existing grid le into FLUENT Use mixed units to dene the geometry and uid properties Set material properties and boundary conditions for a turbulent forced convectionproblem Initiate the calculation with residual plotting

Calculate a solution using the segregated solver

Examine the ow and temperature elds using graphics Enable the second-order discretization scheme for improved prediction of tempera-ture Adapt the grid based on the temperature gradient to further improve the predictionof temperature

Prerequisites

This tutorial assumes that you have little experience with FLUENT, but that you aregenerally familiar with the interface.

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Introduction to Using FLUENT: Fluid Flow and Heat Transfer in a Mixing Elbow

Problem Description

The problem to be considered is shown schematically in Figure 1.1. A cold uid at 26 Centers through the large pipe and mixes with a warmer uid at 40 C in the elbow. Thepipe dimensions are in inches, and the uid properties and boundary conditions are givenin SI units. The Reynolds number at the main inlet is 2.03

105, so that a turbulent

model will be necessary.

Figure 1.1: Problem Specication

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Setup and Solution

Preparation

1. Download introduction.zip from the Fluent Inc. User Services Center(www.fluentusers.com ) to your working directory. This le can be found fromthe Documentation link on the FLUENT product page.OR ,

Copy introduction.zip from the FLUENT documentation CD to your workingdirectory.

For UNIX systems, you can nd the le by inserting the CD into your CD-ROM drive and going to the following directory:

/ cdrom /fluent6.2/help/tutfiles/

where cdrom must be replaced by the name of your CD-ROM drive.For Windows systems, you can nd the le by inserting the CD into your CD-ROM drive and going to the following directory:

cdrom :\fluent6.2\help\tutfiles\

where cdrom must be replaced by the name of your CD-ROM drive (e.g., E).

2. Unzip introduction.zip .elbow.msh can be found in the /introduction folder created after unzipping the le.

3. Start the 2D version of FLUENT.


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Step 1: Grid

1. Read the grid le elbow.msh .

FileRead Case...

(a) Select the le elbow.msh by clicking on it under Files and then clicking on OK.

Note: As this grid is read by FLUENT, messages will appear in the console window reporting the progress of the conversion. After reading the grid le, FLUENTwill report that 918 triangular uid cells have been read, along with a number of boundary faces with different zone identiers.

2. Check the grid.

GridCheck


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3. Smooth (and swap) the grid.

GridSmooth/Swap...

To ensure the best possible grid quality for the calculation, it is good practice tosmooth a triangular or tetrahedral grid after you read it into FLUENT.

(a) Click the Smooth button and then click Swap repeatedly until FLUENTreportsthat zero faces were swapped.

If FLUENT cannot improve the grid by swapping, no faces will be swapped.

(b) Close the panel.

4. Scale the grid.

GridScale...(a) Under Units Conversion, select in from the drop-down list to complete thephrase Grid Was Created In in(inches).

(b) Click Scale to scale the grid.

The reported values of the Domain Extents will be reported in the default SI units of meters.

(c) Click Change Length Units to set inches as the working units for length.

Conrm that the maximum x and y values are 64 inches (see Figure 1.1).


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(d) The grid is now sized correctly, and the working units for length have beenset to inches. Close the panel.

Note: Because the default SI units will be used for everything but the length, therewill be no need to change any other units in this problem. The choice of inches for the unit of length has been made by the actions you have just taken. If you want to change the working units for length to something other than inches,say, mm, you would have to visit the Set Units panel in the Dene pull-down menu.

5. Display the grid (Figure 1.2).

DisplayGrid...

(a) Make sure that all of the surfaces are selected and click Display.


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GridFLUENT 6.2 (2d, segregated, lam)

Figure 1.2: The Triangular Grid for the Mixing Elbow

Extra: You can use the right mouse button to check which zone number corresponds toeach boundary. If you click the right mouse button on one of the boundaries in thegraphics window, its zone number, name, and type will be printed in the FLUENTconsole window. This feature is especially useful when you have several zones of the same type and you want to distinguish between them quickly.


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3. Enable heat transfer by activating the energy equation.

Dene ModelsEnergy...


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Step 3: Materials

1. Create a new material called water.

Dene Materials...(a) Type the name water in the Name text-entry box.

(b) Enter the values shown in the table below under Properties:Property Valuedensity 1000 kg/m 3

C p 4216 J/kg-Kthermal conductivity 0.677 W/m-Kviscosity 8 10 4 kg/m-s

(c) Click Change/Create .


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(d) Click No when FLUENT asks if you want to overwrite air.

The material water will be added to the list of materials which originally con-tained only air. You can conrm that there are now two materials dened by examining the drop-down list under Fluid Materials.

Extra: You could have copied the material water from the materials database(accessed by clicking on the Fluent Database... button). If the propertiesin the database are different from those you wish to use, you can still edit the values under Properties and click the Change/Create button to updateyour local copy. (The database will not be affected.)

(e) Close the Materials panel.


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Step 4: Boundary Conditions

Dene Boundary Conditions...

1. Set the conditions for the uid.

(a) Select uid-9 under Zone.

The Type will be reported as uid.

(b) Click Set... to open the Fluid panel.

(c) Specify water as the uid material by selecting water in the Material Namedrop-down list. Click on OK.


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2. Set the boundary conditions at the main inlet.

(a) Select velocity-inlet-5under Zone and click Set... .

Hint: If you are unsure of which inlet zone corresponds to the main inlet, you can probe the grid display with the right mouse button and the zone ID will

be displayed in the FLUENT console window. In the Boundary Conditionspanel, the zone that you probed will automatically be selected in the Zonelist. In 2D simulations, it may be helpful to return to the Grid Displaypanel and deselect the display of the uid and interior zones (in this case,internal-3) before probing with the mouse button for zone names.


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(b) Choose Components as the Velocity Specication Method.(c) Set an X-Velocityof 0.2 m/s.(d) Retain Y-Velocity at 0 m/s.(e) Set a Temperature of 293 K.

(f) Select Intensity and Hydraulic Diameteras the Turbulence Specication Method.(g) Enter a Turbulence Intensity of 5%, and a Hydraulic Diameterof 32 in.

The hydraulic diameter Dh is dened as:

Dh =4AP w

,

where A is the cross-sectional area and P w is the wetted perimeter. In this2D case, the wetted perimeter for a unit depth slice is equal to 2, since we aremodelling a unit depth slice of a 3D duct that is far removed from the wallson either side.

3. Repeat this operation for velocity-inlet-6, using the values in the following table:velocity specication method components

y velocity 1.0 m/sx velocity 0 m/stemperature 313 Kturbulence specication method intensity & hydraulic diameterturbulence intensity 5%hydraulic diameter 8 in


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4. Set the boundary conditions for pressure-outlet-7, as shown in the panel below.

These values will be used in the event that ow enters the domain through thisboundary.

5. For wall-4, keep the default settings for a Heat Flux of 0.


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6. For wall-8, you will also keep the default settings.

Note: If you probe your display of the grid (without the interior cells) you will seethat wall-8 is the wall on the outside of the bend just after the junction. Thisseparate wall zone has been created for the purpose of doing certain postpro-cessing tasks, to be discussed later in this tutorial.


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Step 5: Solution

1. Initialize the ow eld using the boundary conditions set at velocity-inlet-5.

SolveInitializeInitialize...(a) Choose velocity-inlet-5from the Compute From list.

(b) Add a Y Velocityvalue of 0.2 m/sec throughout the domain.

Note: While an initial X Velocity is an appropriate guess for the horizontal section, the addition of a Y Velocitywill give rise to a better initial guessthroughout the entire elbow.

(c) Click Init and Close the panel.


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2. Enable the plotting of residuals during the calculation.

SolveMonitorsResidual...

(a) Select Plot under Options, and click OK.

Note: By default, all variables will be monitored and checked for determining the

convergence of the solution. Although residuals are used for checking conver-gence, a more reliable method is to dene a surface monitor.


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3. Dene a surface monitor.

SolveMonitorsSurface...

(a) Increase the number of Surface Monitors to 1.(b) Enable Plot and Write.(c) Click Dene... to open the Dene Surface Monitorpanel.

i. Under Report of , select Temperature... and Static Temperature .ii. Under Report Type, select Mass-Weighted Average.

iii. Under Surfaces, select pressure-outlet-7.iv. Click OK.


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4. Save the case le (elbow1.cas ).

FileWrite Case...

Keep the Write Binary Files(default) option on so that a binary le will be written.

5. Start the calculation by requesting 100 iterations.

SolveIterate...(a) Input 100 for the Number of Iterationsand click Iterate.

The solution reaches convergence after approximately 55 iterations. The resid-ual plot and the convergence history of mass-weighted average temperature areshown in Figures 1.3 and 1.4, respectively.


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Note: The number of iterations required for convergence varies according tothe platform used. Also, since the residual values are different for different computers, the plot that appears on your screen may not be exactly thesame as the one shown here.

Scaled ResidualsFLUENT 6.2 (2d, segregated, ske)

Iterations

6050403020100

1e+03

1e+02

1e+01

1e+00

1e-01

1e-02

1e-03

1e-04

1e-05

1e-06

1e-07

epsilonkenergyy-velocityx-velocitycontinuityResiduals

Figure 1.3: Residuals for the First 60 Iterations

6. Check for convergence.

There are no universal metrics for judging convergence. Residual denitions thatare useful for one class of problem are sometimes misleading for other classes of problems. Therefore it is a good idea to judge convergence not only by examiningresidual levels, but also by monitoring relevant integrated quantities and checkingfor mass and energy balances.

The three methods to check for convergence are:

Monitoring the residuals.Convergence will occur when the Convergence Criterionfor each variable hasbeen reached. The default criterion is that each residual will be reduced toa value of less than 10 3, except the energy residual, for which the default

criterion is 10 6

. Solution no longer changes with more iterations.

Sometimes the residuals may not fall below the convergence criterion set inthe case setup. However, monitoring the representative ow variables throughiterations may show that the residuals have stagnated and do not change withfurther iterations. This could also be considered as convergence.


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Convergence history of Static Temperature on pressure-outlet-7FLUENT 6.2 (2d, segregated, ske)

Iteration

(k)Average

WeightedMass

6050403020100

310.0000

308.0000

306.0000

304.0000

302.0000

300.0000

298.0000

296.0000

294.0000

292.0000

290.0000

monitor-1Monitors

Figure 1.4: Convergence History of Mass-Weighted Average Temperature

Overall mass, momentum, energy and scalar balances are obtained.Check the overall mass, momentum, energy and scalar balances in the FluxReports panel. The net imbalance should be less than 0.2% of the net uxthrough the domain.

Report Fluxes


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(a) In the Boundaries list, select pressure-outlet-7, velocity-inlet-5, and velocity-inlet-6.

(b) Click Compute.

7. Save the data le ( elbow1.dat ).

Use the same prex ( elbow1 ) that you used when you saved the case le earlier.Note that additional case and data les will be written later in this session.

FileWrite Data...


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Step 6: Displaying the Preliminary Solution

1. Display lled contours of velocity magnitude (Figure 1.5).

DisplayContours...

(a) Select Velocity... and then Velocity Magnitude from the drop-down lists underContours of .

(b) Select Filled under Options.

(c) Click Display.

Note: Right-clicking on a point in the domain will cause the value of the corre-sponding contour to be displayed in the console window.


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Contours of Velocity Magnitude (m/s)FLUENT 6.2 (2d, segregated, ske)

1.24e+001.18e+001.12e+001.05e+00

9.93e-019.31e-018.69e-018.07e-017.45e-016.82e-016.20e-015.58e-014.96e-014.34e-013.72e-013.10e-012.48e-011.86e-011.24e-016.20e-020.00e+00

Figure 1.5: Predicted Velocity Distribution After the Initial Calculation


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2. Display lled contours of temperature (Figure 1.6).

(a) Select Temperature... and Static Temperature in the drop-down lists underContours of .

(b) Click Display.


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Contours of Static Temperature (k)FLUENT 6.2 (2d, segregated, ske)

3.13e+023.12e+023.11e+023.10e+02

3.09e+023.08e+023.07e+023.06e+023.05e+023.04e+023.03e+023.02e+023.01e+023.00e+022.99e+022.98e+022.97e+022.96e+022.95e+022.94e+022.93e+02

Figure 1.6: Predicted Temperature Distribution After the Initial Calculation


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3. Display velocity vectors (Figure 1.7).

DisplayVectors...(a) Click Display to plot the velocity vectors.

Note: The Auto Scale button is on by default under Options. This scaling

sometimes creates vectors that are too small or too large in the majority of the domain.

(b) Resize the vectors by increasing the Scale factor to 3.

(c) Display the vectors once again.(d) Use the middle mouse button to zoom the view. To do this, hold down the

button and drag your mouse to the right and either up or down to constructa rectangle on the screen. The rectangle should be a frame around the regionthat you wish to enlarge. Let go of the mouse button and the image will beredisplayed (Figure 1.8).

(e) Un-zoom the view by holding down the middle mouse button and dragging itto the left to create a rectangle. When you let go, the image will be redrawn.If the resulting image is not centered, you can use the left mouse button totranslate it on your screen.


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Velocity Vectors Colored By Velocity Magnitude (m/s)FLUENT 6.2 (2d, segregated, ske)

1.40e+001.33e+001.27e+001.20e+001.13e+001.06e+009.96e-019.28e-018.61e-017.94e-017.26e-016.59e-015.91e-015.24e-014.56e-013.89e-013.22e-012.54e-011.87e-011.19e-015.19e-02

Figure 1.7: Resized Velocity Vectors

Velocity Vectors Colored By Velocity Magnitude (m/s)FLUENT 6.2 (2d, segregated, ske)

1.40e+001.33e+001.27e+001.20e+001.13e+001.06e+009.96e-019.28e-018.61e-017.94e-017.26e-016.59e-015.91e-015.24e-014.56e-013.89e-013.22e-012.54e-011.87e-011.19e-015.19e-02

Figure 1.8: Magnied View of Velocity Vectors


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Static TemperatureFLUENT 6.2 (2d, segregated, ske)

Position (in)

(k)Temperature

Static

646260585654525048

3.10e+02

3.08e+02

3.06e+02

3.04e+02

3.02e+02

3.00e+02

2.98e+02

2.96e+02

pressure-outlet

Figure 1.9: Temperature Distribution at the Outlet


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5. Make an XY plot of the static pressure on the outer wall of the large pipe, wall-8(Figure 1.10).

(a) Choose Pressure... and Static Pressure from the Y Axis Functiondrop-downlists.

(b) Deselect pressure-outlet-7 and select wall-8 from the Surfaces list.

(c) Change the Plot Direction for X to 0, and the Plot Direction for Y to 1.

With a Plot Direction vector of (0,1) , FLUENT will plot static pressure at thecells of wall-8 as a function of y.

(d) Click Plot.


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Static PressureFLUENT 6.2 (2d, segregated, ske)

Position (in)

(pascal)Pressure

Static

70605040302010

1.00e+02

0.00e+00

-1.00e+02

-2.00e+02

-3.00e+02

-4.00e+02

-5.00e+02

-6.00e+02

wall-8

Figure 1.10: Pressure Distribution along the Outside Wall of the Bend


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6. Dene a custom eld function for the dynamic head formula ( |V |2/ 2).Dene Custom Field Functions...

(a) In the Field Functionsdrop-down list, select Density and click the Select button.

(b) Click the multiplication button, X.

(c) In the Field Functions drop-down list, select Velocity and Velocity Magnitudeand click Select.

(d) Click y^x to raise the last entry to a power, and click 2 for the power.

(e) Click the divide button, / , and then click 2.

(f) Enter the name dynam-head in the New Function Nametext entry box.(g) Click Dene, and then Close the panel.


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7. Display lled contours of the custom eld function (Figure 1.11).

DisplayContours...

(a) Select Custom Field Functions... in the drop-down list under Contours of .The function you created, dynam-head, will be shown in the lower drop-down

list.(b) Click Display, and then Close the panel.

Note: You may need to un-zoom your view after the last vector display, if you havenot already done so.

8. Write the case and data les to save the settings for the custom eld function.

FileWrite Case & Data...


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Contours of dynam-headFLUENT 6.2 (2d, segregated, ske)

7.70e+02


6.54e+026.93e+027.31e+02

Figure 1.11: Contours of the Custom Field Function, Dynamic Head


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Step 7: Enabling Second-Order Discretization

The elbow solution computed in the rst part of this tutorial uses rst-order discretiza-tion. The resulting solution is very diffusive; mixing is overpredicted, as can be seen in the contour plots of temperature and velocity distribution. You will now change tosecond-order discretization for all listed equations, in order to improve the accuracy of the solution. With the second-order discretization, you will change the gradient option in the solver from cell-based to node-based in order to optimize energy conservation.

1. Change the Gradient Option in the Solver panel.Dene ModelsSolver...(a) Under Gradient Option, select Node-Based.

This option is more suitable than the cell-based gradient option for mesheswith tri-elements (Figure 1.2 ), as it will ensure better energy conservation.

2. Enable the second-order scheme for the calculation of all the listed equations.SolveControls Solution...

(a) Under Discretization, select Second Order for Pressure, Second Order UpwindforMomentum, Turbulence Kinetic Energy, Turbulence Dissipation Rate, and Energy.

(b) Keep the default Under-Relaxation Factors settings.

Note: You will have to scroll down both theDiscretization and Under-RelaxationFactors lists to see the Energy options.


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(c) Click OK.

3. Continue the calculation by requesting 100 more iterations.

SolveIterate...

To save the convergence history for this set of iterations as a separate output le,you can change the File Name in the Dene Surface Monitor to monitor-2.out .The solution converges in approximately 50 additional iterations (Figure 1.12 ). Theconvergence history is shown in Figure 1.13 .


Iterations120100806040200

1e+03

1e+02

1e+01

1e+00

1e-01

1e-02

1e-03

1e-04

1e-05

1e-06

1e-07


Figure 1.12: Residuals for the Second-Order Energy Calculation

Note: Whenever you change the solution control parameters, it is natural to seethe residuals jump.


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Convergence history of Static Temperature on pressure-outlet-7FLUENT 6.2 (2d, segregated, ske)

Iteration

(k)Average

WeightedMass

1101009080706050

304.4000

304.3000

304.2000

304.1000

304.0000

303.9000

303.8000

303.7000

303.6000

monitor-1Monitors

Figure 1.13: Convergence History of Mass-Weighted Average Temperature


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4. Write the case and data les for the second-order solution ( elbow2.cas and elbow2.dat ).

FileWrite Case & Data...(a) Enter the name elbow2 in the Case/Data File box.

(b) Click OK.

The les elbow2.cas and elbow2.dat will be created in your directory.

5. Examine the revised temperature distribution (Figure 1.14).

DisplayContours...

The thermal spreading after the elbow has been reduced from the earlier prediction (Figure 1.6 ).


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3.13e+02


3.10e+023.11e+023.12e+02

Figure 1.14: Temperature Contours for the Second-Order Solution


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Step 8: Adapting the Grid

The elbow solution can be improved further by rening the grid to better resolve the ow details. In this step, you will adapt the grid based on the temperature gradients in thecurrent solution. Before adapting the grid, you will rst determine an acceptable rangeof temperature gradients over which to adapt. Once the grid has been rened, you will continue the calculation.

1. Plot lled contours of temperature on a cell-by-cell basis (Figure 1.15).

DisplayContours...

(a) Select Temperature... and Static Temperature in the Contours of drop-downlists.

(b) Deselect Node Values under Options and click Display.

Note: When the contours are displayed you will see the cell values of temper-

ature instead of the smooth-looking node values. Node values are obtained by averaging the values at all of the cells that share the node. Cell val-ues are the values that are stored at each cell center and are displayed throughout the cell. Examining the cell-by-cell values is helpful when you are preparing to do an adaption of the grid because it indicates the re-gion(s) where the adaption will take place.


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2. Plot the temperature gradients that will be used for adaption (Figure 1.16).

(a) Select Adaption... and Adaption Function in the Contours of drop-down lists.(b) Click Display to see the gradients of temperature, displayed on a cell-by-cell

basis.


3.13e+023.12e+023.11e+023.10e+023.09e+023.08e+023.07e+023.06e+023.05e+023.04e+023.03e+023.02e+023.01e+023.00e+022.99e+022.98e+022.97e+022.96e+022.95e+022.94e+022.93e+02

Figure 1.15: Temperature Contours for the Second-Order Solution: Cell Values


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Contours of Adaption FunctionFLUENT 6.2 (2d, segregated, ske)

1.25e-011.19e-011.13e-011.06e-011.00e-019.39e-028.76e-028.14e-027.51e-026.88e-026.26e-025.63e-025.01e-024.38e-023.75e-023.13e-022.50e-021.88e-021.25e-026.26e-031.42e-14

Figure 1.16: Contours of Adaption Function: Temperature Gradient

Note: The quantity Adaption Function defaults to the gradient of the variablewhose Max and Min were most recently computed in the Contours panel.In this example, the static temperature is the most recent variable to haveits Max and Min computed, since this occurs when the Display button ispushed. Note that for other applications, gradients of another variablemight be more appropriate for performing the adaption.

3. Plot temperature gradients over a limited range in order to mark cells for adaption

(Figure 1.17).(a) Under Options, deselect Auto Range so that you can change the minimum

temperature gradient value to be plotted.

The Min temperature gradient is 0 K/m, as shown in the Contours panel.

(b) Enter a new Min value of 0.02 .

(c) Click Display.

The colored cells in the gure are in the high gradient range, so they will bethe ones targeted for adaption.


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Contours of Adaption FunctionFLUENT 6.2 (2d, segregated, ske)

1.25e-011.20e-011.15e-011.09e-01

1.04e-019.89e-029.36e-028.84e-028.31e-027.78e-027.26e-026.73e-026.21e-025.68e-025.15e-024.63e-024.10e-023.58e-023.05e-022.53e-022.00e-02

Figure 1.17: Contours of Temperature Gradient Over a Limited Range


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4. Adapt the grid in the regions of high temperature gradient.

Adapt Gradient...(a) Select Temperature... and Static Temperature in the Gradients of drop-down

lists.

(b) Deselect Coarsen under Options, so that only a renement of the grid will beperformed.

(c) Click Compute.

FLUENT will update the Min and Max values.

(d) Enter the value of 0.02 for the Rene Threshold.


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(e) Click Mark.

FLUENT will report the number of cells marked for adaption in the consolewindow.

(f) Click Manage... to display the marked cells.

This will open the Manage Adaption Registers panel.

(g) Click Display.

FLUENT will display the cells marked for adaption (Figure 1.18 ).

(h) Click Adapt. Click Yes when you are asked for conrmation.

Note: There are two different ways to adapt. You can click on Adapt in theManage Adaption Registerspanel as was just done, or Close this panel and

do the adaption in the Gradient Adaption panel. If you use the Adaptbutton in the Gradient Adaption panel, FLUENT will recreate an adaption register. Therefore, once you have the Manage Adaption Registers panel open, it saves time to use the Adapt button there.

(i) Close the Manage Adaption Registersand Gradient Adaption panels.


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Adaption Markings (gradient-r0)FLUENT 6.2 (2d, segregated, ske)

Figure 1.18: Cells Marked for Adaption


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5. Display the adapted grid (Figure 1.19).

DisplayGrid...

GridFLUENT 6.2 (2d, segregated, ske)

Figure 1.19: The Adapted Grid

6. Request an additional 100 iterations.

SolveIterate...

The solution converges after approximately 50 additional iterations.

7. Write the nal case and data les ( elbow3.cas and elbow3.dat ) using the prexelbow3 .

FileWrite Case & Data...


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Iterations160140120100806040200

1e+03

1e+02

1e+01

1e+00

1e-01

1e-02

1e-03

1e-04

1e-05

1e-06

1e-07


Figure 1.20: The Complete Residual History

Convergence history of Static Temperature on pressure-outlet-7 FLUENT 6.2 (2d, segregated, ske)

Iteration

(k)Average

WeightedMass

150145140135130125120115110105

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