Fluent Tutorial

FLUENT 6.2 Tutorial Guide

January 2005

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, andPOLYFLOW are registered trademarks of Fluent Inc. All other products or name

brands 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

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 Flow5 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 Model14 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 Solidification21 Using the Eulerian Granular Multiphase Model with Heat Transfer22 Postprocessing23 Turbo Postprocessing24 Parallel Processing

Using This Manual

Whats In This Manual

The FLUENT Tutorial Guide contains a number of tutorials that teach you how to useFLUENT to 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 FLUENT and its interface. In these tutorials, somesteps 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-specificpostprocessing.

Where to Find the Files Used in the Tutorials

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

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

How To Use This Manual

Depending on your familiarity with computational fluid 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 FLUENT you should first read and solve Tutorial 1, in orderto familiarize yourself with the interface and with basic setup and solution procedures.

c Fluent Inc. January 11, 2005 i

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 specific features, suchas custom field 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-specific 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 specific features, suchas custom field 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-specific 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 and

text 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.

ii c Fluent Inc. January 11, 2005

Using This Manual

A mini flow chart is used to indicate the menu selections that lead you to a specificcommand or panel. For example,

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

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

c Fluent Inc. January 11, 2005 iii

Using This Manual

iv c Fluent Inc. January 11, 2005

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

Step 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 . . . . . . . . . . . . . . . 1-38

Step 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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2

Step 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


Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1



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

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

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

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


Step 5: Solution for the Rosseland Model . . . . . . . . . . . . . . . . . . 5-13

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

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

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

Step 9: DO Model Definition, 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 Definition, 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 Definition, 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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-3

Step 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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-20

Step 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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-3

Step 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

Prerequisites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 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




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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



Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-2

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

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

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

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




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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-3

Step 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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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 1: Grid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14-4

Step 2: Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14-7

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

c Fluent Inc. January 11, 2005 ix

CONTENTS

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 1: Grid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-3

Step 2: Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-5

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

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



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


Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 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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CONTENTS

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



Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 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 . . . . . . . . . . . . . . . . . 18-18

Step 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 Solidification 20-1

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

Prerequisites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20-1



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

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

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

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


Step 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

xii c Fluent Inc. January 11, 2005

CONTENTS

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

Prerequisites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22-10

Step 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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CONTENTS

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: Defining 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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24-1

Prerequisites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 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

xiv c Fluent Inc. January 11, 2005

CONTENTS

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

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


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

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xvi c Fluent Inc. January 11, 2005

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

Introduction

This tutorial illustrates the setup and solution of the two-dimensional turbulent fluid flowand heat transfer in a mixing junction. The mixing elbow configuration is encounteredin piping systems in power plants and process industries. It is often important to predictthe flow field and temperature field 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 file into FLUENT Use mixed units to define the geometry and fluid properties Set material properties and boundary conditions for a turbulent forced convection

problem

Initiate the calculation with residual plotting Calculate a solution using the segregated solver Examine the flow and temperature fields 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.

c Fluent Inc. January 11, 2005 1-1

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 fluid at 26Centers through the large pipe and mixes with a warmer fluid at 40C in the elbow. Thepipe dimensions are in inches, and the fluid properties and boundary conditions are givenin SI units. The Reynolds number at the main inlet is 2.03 105, so that a turbulentmodel will be necessary.

Figure 1.1: Problem Specification

1-2 c Fluent Inc. January 11, 2005


Setup and Solution

Preparation

1. Download introduction.zip from the Fluent Inc. User Services Center(www.fluentusers.com) to your working directory. This file 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 find the file by inserting the CD into your CD-ROMdrive 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 find the file by inserting the CD into your CD-ROMdrive 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 thefile.

3. Start the 2D version of FLUENT.



Step 1: Grid

1. Read the grid file elbow.msh.

File Read Case...

(a) Select the file 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 windowreporting the progress of the conversion. After reading the grid file, FLUENTwill report that 918 triangular fluid cells have been read, along with a numberof boundary faces with different zone identifiers.

2. Check the grid.

Grid Check



Grid Check

Domain Extents:x-coordinate: min (m) = 0.000000e+00, max (m) = 6.400001e+01y-coordinate: min (m) = -4.538534e+00, max (m) = 6.400000e+01

Volume statistics:minimum volume (m3): 2.782193e-01maximum volume (m3): 3.926232e+00

total volume (m3): 1.682930e+03Face area statistics:minimum face area (m2): 8.015718e-01maximum face area (m2): 4.118252e+00

Checking number of nodes per cell.Checking number of faces per cell.Checking thread pointers.Checking number of cells per face.Checking face cells.Checking bridge faces.Checking right-handed cells.Checking face handedness.Checking element type consistency.Checking boundary types:Checking face pairs.Checking periodic boundaries.Checking node count.Checking nosolve cell count.Checking nosolve face count.Checking face children.Checking cell children.Checking storage.Done.

Note: The minimum and maximum values may vary slightly when running ondifferent platforms. The grid check lists the minimum and maximum x andy values from the grid, in the default SI units of meters, and reports on anumber of other grid features that are checked. Any errors in the grid wouldbe reported at this time. In particular, you should always make sure that theminimum volume is not negative, since FLUENT cannot begin a calculation ifthis is the case. To scale the grid to the correct units of inches, the Scale Gridpanel will be used.



3. Smooth (and swap) the grid.

Grid Smooth/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 FLUENT reportsthat 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.

Grid Scale...(a) Under Units Conversion, select in from the drop-down list to complete the

phrase 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 SIunits of meters.

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

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



(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 inchesfor the unit of length has been made by the actions you have just taken. If youwant 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 Define pull-downmenu.

5. Display the grid (Figure 1.2).

Display Grid...

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



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 ofthe same type and you want to distinguish between them quickly.



Step 2: Models

1. Keep the default solver settings.

Define Models Solver...

2. Turn on the standard k- turbulence model.

Define Models Viscous...(a) Select k-epsilon in the Model list.

The original Viscous Model panel will expand when you do so.

(b) Accept the default Standard model by clicking OK.



3. Enable heat transfer by activating the energy equation.

Define Models Energy...



Step 3: Materials

1. Create a new material called water.

Define 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/m3

Cp 4216 J/kg-Kthermal conductivity 0.677 W/m-Kviscosity 8 104 kg/m-s

(c) Click Change/Create.



(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 confirm that there are now two materials defined byexamining 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 editthe values under Properties and click the Change/Create button to updateyour local copy. (The database will not be affected.)

(e) Close the Materials panel.



Step 4: Boundary Conditions

Define Boundary Conditions...

1. Set the conditions for the fluid.

(a) Select fluid-9 under Zone.

The Type will be reported as fluid.

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

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



2. Set the boundary conditions at the main inlet.

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

Hint: If you are unsure of which inlet zone corresponds to the main inlet, youcan probe the grid display with the right mouse button and the zone ID willbe 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 fluid and interior zones (in this case,internal-3) before probing with the mouse button for zone names.



(b) Choose Components as the Velocity Specification Method.

(c) Set an X-Velocity of 0.2 m/s.

(d) Retain Y-Velocity at 0 m/s.

(e) Set a Temperature of 293 K.

(f) Select Intensity and Hydraulic Diameter as the Turbulence Specification Method.

(g) Enter a Turbulence Intensity of 5%, and a Hydraulic Diameter of 32 in.

The hydraulic diameter Dh is defined as:

Dh =4A

Pw,

where A is the cross-sectional area and Pw 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 specification method componentsy velocity 1.0 m/sx velocity 0 m/stemperature 313 Kturbulence specification method intensity & hydraulic diameterturbulence intensity 5%hydraulic diameter 8 in



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

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

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



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.



Step 5: Solution

1. Initialize the flow field using the boundary conditions set at velocity-inlet-5.

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

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

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

(c) Click Init and Close the panel.



2. Enable the plotting of residuals during the calculation.

Solve Monitors Residual...

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

Note: By default, all variables will be monitored and checked for determining theconvergence of the solution. Although residuals are used for checking conver-gence, a more reliable method is to define a surface monitor.



3. Define a surface monitor.

Solve Monitors Surface...

(a) Increase the number of Surface Monitors to 1.

(b) Enable Plot and Write.

(c) Click Define... to open the Define Surface Monitor panel.

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.



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

File Write Case...

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

5. Start the calculation by requesting 100 iterations.

Solve Iterate...(a) Input 100 for the Number of Iterations and 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.



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

Scaled ResidualsFLUENT 6.2 (2d, segregated, ske)

Iterations6050403020100

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 definitions thatare useful for one class of problem are sometimes misleading for other classes ofproblems. 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 Criterion for each variable hasbeen reached. The default criterion is that each residual will be reduced toa value of less than 103, except the energy residual, for which the defaultcriterion is 106.

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 flow variables throughiterations may show that the residuals have stagnated and do not change withfurther iterations. This could also be considered as convergence.



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 fluxthrough the domain.

Report Fluxes



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

(b) Click Compute.

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

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

File Write Data...



Step 6: Displaying the Preliminary Solution

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

Display Contours...

(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.



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

1.24e+001.18e+001.12e+001.05e+009.93e-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



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

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

(b) Click Display.



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

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 1.6: Predicted Temperature Distribution After the Initial Calculation



3. Display velocity vectors (Figure 1.7).

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

Note: The Auto Scale button is on by default under Options. This scalingsometimes creates vectors that are too small or too large in the majorityof 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 thebutton 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.



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: Magnified View of Velocity Vectors



4. Create an XY plot of temperature across the exit (Figure 1.9).

Plot XY Plot...

(a) Select Temperature... and Static Temperature in the drop-down lists under theY Axis Function.

(b) Select pressure-outlet-7 from the Surfaces list.

(c) Click Plot.



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-7

Figure 1.9: Temperature Distribution at the Outlet



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 Function drop-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.



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



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

(a) In the Field Functions drop-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 Name text entry box.

(g) Click Define, and then Close the panel.



7. Display filled contours of the custom field function (Figure 1.11).

Display Contours...

(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-downlist.

(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 files to save the settings for the custom field function.

File Write Case & Data...



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

7.70e+02

0.00e+003.85e+017.70e+011.15e+021.54e+021.92e+022.31e+022.69e+023.08e+023.46e+023.85e+024.23e+024.62e+025.00e+025.39e+025.77e+026.16e+026.54e+026.93e+027.31e+02

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



Step 7: Enabling Second-Order Discretization

The elbow solution computed in the first part of this tutorial uses first-order discretiza-tion. The resulting solution is very diffusive; mixing is overpredicted, as can be seenin 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 ofthe solution. With the second-order discretization, you will change the gradient option inthe solver from cell-based to node-based in order to optimize energy conservation.

1. Change the Gradient Option in the Solver panel.

Define Models Solver...(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.

Solve Controls Solution...

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

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

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



(c) Click OK.

3. Continue the calculation by requesting 100 more iterations.

Solve Iterate...

To save the convergence history for this set of iterations as a separate output file,you can change the File Name in the Define 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.




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




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

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

(b) Click OK.

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

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

Display Contours...

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




3.13e+02

2.93e+022.94e+022.95e+022.96e+022.97e+022.98e+022.99e+023.00e+023.01e+023.02e+023.03e+023.04e+023.05e+023.06e+023.07e+023.08e+023.09e+023.10e+023.11e+023.12e+02

Figure 1.14: Temperature Contours for the Second-Order Solution



Step 8: Adapting the Grid

The elbow solution can be improved further by refining the grid to better resolve the flowdetails. In this step, you will adapt the grid based on the temperature gradients in thecurrent solution. Before adapting the grid, you will first determine an acceptable rangeof temperature gradients over which to adapt. Once the grid has been refined, you willcontinue the calculation.

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

Display Contours...

(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 obtainedby 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 displayedthroughout the cell. Examining the cell-by-cell values is helpful when youare preparing to do an adaption of the grid because it indicates the re-gion(s) where the adaption will take place.



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-cellbasis.



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



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 minimumtemperature 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 figure are in the high gradient range, so they will bethe ones targeted for adaption.



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

1.25e-011.20e-011.15e-011.09e-011.04e-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



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 refinement 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 Refine Threshold.



(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 confirmation.

Note: There are two different ways to adapt. You can click on Adapt in theManage Adaption Registers panel as was just done, or Close this panel anddo the adaption in the Gradient Adaption panel. If you use the Adaptbutton in the Gradient Adaption panel, FLUENT will recreate an adaptionregister. Therefore, once you have the Manage Adaption Registers panelopen, it saves time to use the Adapt button there.

(i) Close the Manage Adaption Registers and Gradient Adaption panels.



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

Figure 1.18: Cells Marked for Adaption



5. Display the adapted grid (Figure 1.19).

Display Grid...

GridFLUENT 6.2 (2d, segregated, ske)

Figure 1.19: The Adapted Grid

6. Request an additional 100 iterations.

Solve Iterate...

The solution converges after approximately 50 additional iterations.

7. Write the final case and data files (elbow3.cas and elbow3.dat) using the prefixelbow3.

File Write Case & Data...




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


Iteration

(k)Average

WeightedMass

150145140135130125120115110105100

304.2000

304.1500

304.1000

304.0500

304.0000

303.9500

303.9000

303.8500

303.8000

monitor-1Monitors




8. Examine the filled temperature distribution (using node values) on the revised grid(Figure 1.22).

Display Contours...



Figure 1.22: Filled Contours of Temperature Using the Adapted Grid

Summary

Comparison of the filled temperature contours for the first solution (using the originalgrid and first-order discretization) and the last solution (using an adapted grid andsecond-order discretization) clearly indicate that the latter is much less diffusive. Whilefirst-order discretization is the default scheme in FLUENT, it is good practice to useyour first-order solution as a starting guess for a calculation that uses a higher-orderdiscretization scheme and, optionally, an adapted grid.

Note that in this problem, the flow field is decoupled from temperature since all propertiesare constant. For such cases, it is more efficient to compute the flow-field solution first(i.e., without solving the energy equation) and then solve for energy (i.e., without solvingthe flow equations). You will use the Solution Controls panel to turn solution of theequations on and off during this procedure.


Tutorial 2. Modeling Periodic Flow and Heat Transfer

Introduction

Many industrial applications, such as steam generation in a boiler or air cooling in thecoil of an air conditioner, can be modeled as two-dimensional periodic heat flow. Thistutorial illustrates how to set up and solve a periodic heat transfer problem, given apregenerated mesh.

The system that is modeled is a bank of tubes containing a flowing fluid at one temper-ature that is immersed in a second fluid in cross-flow at a different temperature. Bothfluids are water, and the flow is classified as laminar and steady, with a Reynolds numberof approximately 100. The mass flow rate of the cross-flow is known, and the model isused to predict the flow and temperature fields that result from convective heat transfer.

Due to symmetry of the tube bank and the periodicity of the flow inherent in the tubebank geometry, only a portion of the geometry will be modeled in FLUENT, with sym-metry applied to the outer boundaries. The resulting mesh consists of a periodic modulewith symmetry. In the tutorial, the inflow boundary will be redefined as a periodic zone,and the outflow boundary defined as its shadow.

In this tutorial you will learn how to:

Create periodic zones. Define a specified periodic mass flow rate. Model periodic heat transfer with specified temperature boundary conditions. Calculate a solution using the segregated solver. Plot temperature profiles on specified isosurfaces.

Prerequisites

This tutorial assumes that you are familiar with the menu structure in FLUENT and thatyou have completed Tutorial 1 . Some steps in the setup and solution procedure will notbe shown explicitly.


Modeling Periodic Flow and Heat Transfer

Problem Description

This problem considers a 2D section of a tube bank. A schematic of the problem isshown in Figure 2.1. The bank consists of uniformly spaced tubes with a diameter of 1cm, that are staggered in the direction of cross-fluid flow. Their centers are separated bya distance of 2 cm in the x direction, and 1 cm in the y direction. The bank has a depthof 1 m.

1 cm

= 300 K

4 cm

0.5 cm

wall = 400 K{m = 0.05 kg/s

= 998.2 kg/m3

= 0.001003 kg/m-s= 4182 J/kg-K

= 0.6 W/m-K

c pk

Figure 2.1: Schematic of the Problem

Because of the symmetry of the tube bank geometry, only a portion of the domain needsto be modeled. The computational domain is shown in outline in Figure 2.1. A massflow rate of 0.05 kg/s is applied to the inflow boundary of the periodic module. Thetemperature of the tube wall (Twall) is 400 K and the bulk temperature of the cross-flowwater (T) is 300 K. The properties of water that are used in the model are shown inFigure 2.1.



Setup and Solution

Preparation

1. Download periodic_flow_heat.zip from the Fluent Inc. User Services Centeror copy it from the FLUENT documentation CD to your working directory (asdescribed in Tutorial 1).

2. Unzip periodic_flow_heat.zip.

tubebank.msh can be found in the /periodic flow heat folder created after un-zipping the file.

3. Start the 2D version of FLUENT.

Step 1: Grid

1. Read the mesh file, tubebank.msh.

File Read Case...2. Check the grid.

Grid CheckFLUENT will perform various checks on the mesh and report the progress in theconsole window. Make sure that the minimum volume reported is a positive num-ber.

3. Scale the grid.

Grid Scale...

(a) Under Units Conversion, select cm (centimeters) from the drop-down list tocomplete the phrase Grid Was Created In cm.

(b) Click Scale to scale the grid and close the panel.



4. Display the mesh (Figure 2.2).

Display Grid...

GridFLUENT 6.2 (2d, segregated, lam)

Figure 2.2: Mesh for the Periodic Tube Bank



Quadrilateral cells are used in the regions surrounding the tube walls, and triangularcells are used for the rest of the domain, resulting in a hybrid mesh (See Figure 2.2).The quadrilateral cells provide better resolution of the viscous gradients near thetube walls. The remainder of the computational domain is conveniently filled withtriangular cells.

Extra: Right-click on one of the boundaries in the graphics window to check whichzone number corresponds to the boundary. The zone number, name, and typewill be printed in the FLUENT console window. This feature is especially usefulwhen there are several zones of the same type and you want to distinguishbetween them.

5. Create the periodic zone.

The inflow (wall-9) and outflow (wall-12) boundaries currently defined as wall zonesneed to be redefined as periodic. Redefine the wall-9 boundary as translationallyperiodic zone, and wall-12 as periodic shadow of wall-9.

(a) In the console window, enter the inputs shown in boxes in the following dialog.

Hint: Press to get the command prompt (>).

grid/modify-zones/make-periodic

Periodic zone [()] 9

Shadow zone [()] 12

Rotational periodic? (if no, translational) [yes] no

Create periodic zones? [yes] yes

Auto detect translation vector? [yes] yes

computed translation deltas: 0.040000 0.000000

all 26 faces matched for zones 9 and 12.

zone 12 deleted

created periodic zones.



Step 2: Models

1. Keep the default solver settings.

Define Models Solver...

2. Enable heat transfer by activating the energy equation.

Define Models Energy...



3. Set the periodic flow conditions.

Define Periodic Conditions...

(a) Under Type, select Specify Mass Flow.

This will allow you to specify the Mass Flow Rate.

(b) For Mass Flow Rate, enter a value of 0.05 and click OK.



Step 3: Materials

Add liquid water to the list of fluid materials by copying it from the materials database.

1. Copy the properties of liquid water from the database.

Define Materials...(a) Click on the Fluent Database... button.

This will open the Fluent Database Materials panel.

(b) Select water-liquid (h2o) from the Fluent Fluid Materials list.

This will display the default settings for water-liquid. You will have to scrolldown the Fluent Fluid Materials list to see the entries.

(c) Click Copy and Close the panel.

The Materials panel will now display the copied information of water.



Step 4: Boundary Conditions

Define Boundary Conditions...

1. Set the conditions for fluid-16.

(a) In the Material Name drop-down list, select water-liquid



2. Set the boundary conditions for wall-21.

This is the bottom wall of the left tube in the periodic module shown in Figure 2.1.

(a) Change Zone Name to wall-bottom.

(b) Under Thermal Conditions, select Temperature.

(c) Set the Temperature to 400 K.



3. Set the boundary conditions for wall-3.

This is the top wall of the right tube in the periodic module shown in Figure 2.1.

(a) Change the Zone Name to wall-top.

(b) Under Thermal Conditions, select Temperature.

(c) Set the Temperature to 400 K.

(d) Click OK to close the panel.



Step 5: Solution

1. Set the solution parameters.

Solve Controls Solution...

(a) Set the Under-Relaxation Factor for Energy to 0.9.

Hint: Scroll down the Under-Relaxation Factors list to see Energy.

(b) Under Discretization, select Second Order Upwind for Momentum and Energy.



2. Enable the plotting of residuals.

Solve Monitors Residual...

(a) Under Options, enable Plot and click OK.

3. Initialize the solution.

Solve Initialize Initialize...



(a) Under Initial Values, check that the value f

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