User Manual
HEXPRESS™v4
Unstructured Grid Generator
-HEXPRESS™ v4
Documentation v4a
NUMECA International
Chaussée de la Hulpe, 189, Terhulpsesteenweg
B-1170 Brussels
BELGIUM
Tel: +32 2 647.83.11
Fax: +32 2 647.93.98
Web: http://www.numeca.com
CHAPTER 1: Getting Started 1-1 1-1 Overview 1-1 1-2 Introduction 1-1 What is HEXPRESS™ 1-1 Features 1-1 Structured vs. Unstructured 1-2 Approach 1-3 Project Management 1-4
1-3 How to Use This Manual 1-4
Outline 1-4
Conventions 1-5
1-4 First Time Use 1-5
Basic Installation 1-5
Expert Graphics Options 1-6
Graphics Driver 1-6
1-5 How to Start HEXPRESS™ Interface 1-6
1-6 Required Licenses 1-7
Standard HEXPRESS™ License 1-7
Additional Licenses 1-7
CHAPTER 2: User Interface 2-1
2-1 Overview 2-1
2-2 Welcome Dialog Box 2-2
2-3 Menu Bar 2-3
Project Menu 2-4
Project/New 2-4
Project/Open 2-4
Structured project for turbomachinery applications 2-4
Structured project for marine applications 2-5
Project/Save 2-6 Project/Save as... 2-7 Project/Import... 2-8 Project/Import.../Project 2-8 Project/Import.../Domain 2-8 Project/Import.../.dat 2-8 Project/Import.../Parasolid 2-9 Project/Import.../STL triangulation 2-10 Project/Import.../CATIA v5 model 2-10 Project/Import.../ANSYS mesh 2-11 Project/Import.../CGNS mesh 2-11 Project/Import.../HEXPRESS/Hybrid mesh 2-11 Project/Export 2-11 Project/Export.../StarCD 2-11 Project/Export.../Fluent 2-13 Project/Export.../Samcef-Bacon 2-15 Project/Export.../CGNS 2-16 Project/Export.../NASTRAN 2-17 Project/Export.../OpenFOAM 2-17 Project/Export.../CEDRE 2-18
Project/Export.../CEDRE (short names) 2-18
Project/Clear cache... 2-18
Project/Print/As PNG 2-19 Project/Preferences... 2-19 Project/Quit 2-22 Internal Surface 2-22 Internal Surface/Edit 2-22 Edit->Copy 2-22 Edit->Translate 2-22 Edit->Rotate 2-23 Edit->Scale 2-23 Edit->Mirror 2-23
Internal Surface/Modify Curve 2-23
Modify Curve->Add Control Point 2-24
Modify Curve->Remove Control Point 2-24
Modify Curve->Modify Point 2-24
Modify Curve->Modify Point On Surface 2-25
Modify Curve->Discretization 2-25
Modify Curve->Divide 2-25
Modify Curve->Reverse Orientation 2-25
Modify Curve -> Set Name 2-25
Internal Surface/Modify Surface 2-26
Modify Surface-> Set Name 2-26
Internal Surface/Select 2-26 Select->Cartesian Points 2-26 Select->Curves 2-26 Select->Surfaces 2-27 Internal Surface/View 2-27 View->Points 2-28 View->Curves 2-28 View->Surfaces 2-29
View->Hide Selected Cartesian Points 2-30
View->Hide Selected Curves 2-30
View->Hide Selected Surfaces 2-30
View->Control Points 2-30
View->Curve Orientation 2-30
Internal Surface/Delete 2-30
Delete Cartesian Points 2-31
Delete->Curves 2-31 Delete->Surfaces 2-31 Grid Menu 2-31 Grid/Periodicity... 2-31 Grid/Boundary Conditions... 2-33 Face selection 2-34 Filters 2-36 Face grouping 2-37
Face type specification 2-37
Face name 2-37
Blank/Unblank 2-37
Periodic BC search 2-38
Grid/Non Matching Connections... 2-38
Full Non Matching Connections 2-38
Rotor/Stator Connections 2-43
Negative cells 2-46
Concave and twisted cells 2-47
Orthogonality 2-47
Aspect ratio 2-47
Volume criterion 2-47
Equi-angular skewness 2-47
Adjacent cell volume ratio 2-48
Mesh expansion ratio 2-48
Cell non-orthogonality (OpenFOAM) 2-49
Cell non-orthogonality (FINE™/Marine) 2-49
Surface Mesh Quality 2-50
Relaxed Cells 2-50 Manual Correction 2-51 Grid/Mesh transformation... 2-52 Rotate 2-52 Translate 2-53 Scale 2-54 Axisymmetric 2-54
Mirror and Copy 2-56
Grid/Multigrid levels... 2-57 View Menu 2-57 Face Viewer 2-57 View/Cells... 2-58 View/Face Displacement 2-58 View/Insert Text 2-59 View/Delete Text 2-59 View/Perspective 2-59 View/Repetition... 2-60 STL 2-60 Tools 2-60 STARCD->STL 2-60 Domain->ASCII STL or binary STL 2-60 Tools/Distance 2-60 Plugins 2-61 Concept 2-61
How to activate them? 2-62
Marine Plugins 2-62
Domain and mesh setup (only for 3D) 2-63
Domhydro 2-67
Assumptions 2-67
Modes Description 2-68
How to use the tool 2-69
How to launch the tool 2-69
Examples 2-72
Internal surface creation 2-74
Mesh quality check 2-75
Set type II on mirror faces 2-76
2-4 Toolbar 2-76
2-5 Quick Access Pad 2-77
CAD Manipulation 2-77
Internal Surface 2-78
Point page 2-79
Cartesian Point 2-79
Curve page 2-79 Polyline 2-79 CSpline 2-80 Arc 2-80 Surface page 2-84 Lofted 2-84 Coons 2-85 Import 2-85 Export 2-85 Domain Manipulation 2-86 Mesh Wizard 2-86 View 2-87 Domains 2-87 Display Options 2-87 Material 2-91 Mesh 2-93 Background 2-94 Camera Position 2-94 Control Area 2-95 Message area 2-95
Keyboard input area 2-95
Mouse coordinates 2-95
Information area 2-95
Grid parameters area 2-96
Viewing buttons 2-96
X, Y, and Z projection buttons 2-96
Coordinate axis 2-96
Scrolling 2-97
3D viewing button 2-97
Rotate about x, y or z axis 2-97
Zoom in/out 2-97
Region zoom 2-98
Fit button 2-98
Original button 2-98
Cutting Plane 2-98
Cylindrical cutting tool 2-100
Box cutting tool 2-101
Spherical cutting tool 2-101
Graphics Area & Views 2-102
2-6 GUI interaction 2-102
Keyboard shortcuts 2-102
CHAPTER 3: Meshing Fundamentals 3-1
3-1 Overview 3-1
3-2 Mesh Domain Definition 3-2
3-3 Mesh Generation Steps 3-4
Initial Mesh 3-4 Adapt to geometry 3-4 Refinement 3-4 Trimming 3-5 Snap to geometry 3-6 Optimization 3-6
Viscous layers 3-7
3-4 Mesh Quality 3-7
3-5 Multi-Domain 3-7
3-6 Batch Mode 3-8
CHAPTER 4: Geometry Definition 4-1
4-1 Overview 4-1
4-2 CAD Model 4-4
Import Solid Models 4-4
Import Parasolid™ models 4-4
Import CATIA V5 models 4-4
Editing 4-5 Create Box 4-5 Dialog box 4-5 Interactive creation 4-6 Create Cylinder 4-6 Dialog box 4-6 Interactive creation 4-7 Create Cone 4-7 Dialog box 4-7 Interactive creation 4-8 Create Plane 4-8 Dialog box 4-8 Interactive creation 4-9 Create Sphere 4-10 Dialog box 4-10 Interactive creation 4-10 Subtract 4-11 Overview 4-11
Body picking description 4-11
How to subtract bodies? 4-11
Unite 4-11
Overview 4-11
Body picking description 4-12
How to unite bodies? 4-12
Intersect 4-13
Overview 4-13
Body picking description 4-13
How to intersect bodies? 4-13
Delete 4-14
Overview 4-14
Body picking description 4-14
How to delete bodies? 4-14
Transform 4-14
Undo 4-15
Create Domain 4-15
Faceting 4-16
Discretized CAD manipulation 4-17
Export parameters 4-17
Save 4-18
Visualization/Selection 4-18
Selection 4-18
4-3 STL Model 4-20
Introduction 4-20
What is STL? 4-20
STL representation of the computational domain 4-20
Import 4-21 STL Manipulation 4-21 STL Group Tool 4-21 STL Manipulation Menu 4-21 Viewing/Selection 4-22 Manipulation 4-24 STL/Edit 4-25 Mirror geometry 4-25 Translate geometry 4-25 Rotate geometry 4-25 Clear all 4-25 Information 4-25 STL/Export... 4-27 Ascii stl format 4-27 Binary stl format 4-27
4-4 StarCD Surface Mesh 4-27
4-5 Internal Surface Geometry 4-28
CHAPTER 5: Domain Manipulation 5-1
5-1 Overview 5-1
5-2 Domain Definition 5-1
5-3 Domain Manipulation 5-2
CHAPTER 6: Mesh Wizard 6-1
6-1 Overview 6-1
6-2 Mesh Wizard Actions 6-2
Check Action 6-2
Execute Action 6-3
Common Action Buttons 6-4
6-3 2D/3D Mesh Generation 6-4
Geometry Constraints for 2D projects 6-4
Geometry Constraints for axi-symmetric project 6-5
6-4 Imposing Boundary Conditions 6-7
6-5 Initial Mesh 6-7
Overview 6-7
Domain Bounding Box Subdivision 6-8
Description 6-8
Specify maximum total number of cells 6-8
Auto button 6-8
Specify divisions of the bounding box 6-8
Cylindrical Mesh 6-9
Description 6-9
Sector Parameters 6-9
Number of Divisions 6-9
Import Mesh File 6-10
6-6 Adapt To Geometry 6-10
Overview 6-10
Refinement 6-12
Global Parameters 6-13
Maximum number of refinements 6-14
Advanced parameters 6-14
Enable refinement 6-14
Enable trimming 6-14
Refinement diffusion 6-14
Number of cells in gaps 6-15
Minimum cell size 6-16
Maximum cell size 6-16
Prevent refinement of exterior cells 6-16
Impose isotropic refinement near domain corners 6-16
Apply trimming by distance 6-17
Curve Refinement 6-17
Surface Refinement 6-18
Surface Selection 6-19
Using surfaces list 6-19
By picking 6-20
Rectangle Selection 6-20
Select Identical 6-20
Using Select button 6-20
Zoom In 6-21
Blank/Unblank 6-21
Invert Selection 6-21
Undo Selection 6-21
Different settings highlight 6-21
Surface Grouping 6-22 Active 6-22 Refinement 6-22 Adaptation Criteria 6-23 Distance criterion 6-23 Curvature criterion 6-24
Target cell sizes criterion 6-25
Combining refinement criteria 6-26
Advanced parameters 6-26
Aspect ratio 6-26
Curvature ref factor (R/C) 6-26
Anisotropic extent 6-27 Refinement diffusion 6-28 Box Refinement 6-28 Volume Box 6-29 Cylindrical Sector 6-29 Active 6-29
Adaptation box transformation 6-30
Parameters 6-30
Target Cell Sizes 6-31
Volumic refinement 6-31
Refinement Diffusion 6-31
Interaction Volume-Surface Criteria 6-31
Trimming Parameters 6-32
Best Practice 6-33
Using distance surface criterion 6-33
No cell in domain after trimming 6-33
6-7 Snap to geometry 6-33
Advanced flags 6-34 Snap on surfaces 6-34 Capture corners 6-35 Capture curves 6-35 Projection on surfaces 6-35 Buffer insertion 6-35 Mesh smoothing 6-36
Partial Curve Snapping 6-36
Buffer Insertion 6-37
Best Practice 6-39
Which entity has not been snapped correctly? 6-39
How to locate them? 6-39
How to handle these issues? 6-40
6-8 Optimization 6-42 Overview 6-42 Advanced 6-43 Relaxing Geometry 6-43 Other Parameters 6-44 6-9 Viscous Layers 6-45 Overview 6-45 Global Menu 6-46 Global parameters 6-46
Fixed first layer thickness 6-46
Fixed stretching ratio 6-47
Control parameters 6-47
Fixed first layer thickness method 6-47
Variable first layer thickness method 6-49
Surface Settings 6-50
Surface Selection 6-50
Using surfaces list 6-50
By picking 6-51 Rectangle Selection 6-51 Enable/Disable 6-51 Select Identical 6-51 Zoom In 6-51 Invert Selection 6-51 Undo Selection 6-51
Different settings highlight 6-51
Surface Grouping 6-52
Active 6-52
Parameters 6-52
For fixed first layer thickness method 6-52
For variable first layer thickness method 6-53
Troubleshooting 6-55
CHAPTER 7: Python Scripts and Plugins 7-1
7-1 Overview 7-1 7-2 Project Commands 7-2 7-3 Viewing Commands 7-4 Camera position 7-4 7-4 Geometry Commands 7-4 Global Functions 7-4 CAD Commands 7-4
STL Commands 7-6
Box Class Commands 7-7
Member functions 7-7
BoxRTZ Class Commands 7-7
Domain Commands 7-8
CartesianPoint class 7-8
Curve Construction 7-9
Member functions 7-9
Internal Surface Commands 7-10
Member functions 7-10 Body Class 7-10 Member functions 7-10 BodyFace Class 7-10 Member functions 7-10 BodyEdge Class 7-11 Member functions 7-11 Domain Class 7-11 Member functions 7-11
7-5 Mesh Generation Commands 7-13
Global Functions 7-13 DomainFace Class 7-17 Member functions 7-17 DomainEdge Class 7-18 Member functions 7-19 DomainVertex Class 7-20 Member functions 7-20 SurfaceAdaptationGroup class 7-20 EdgeAdaptationGroup class 7-21 RefinementBox class 7-22 VLGroup class 7-23 FNMB class 7-23
7-6 Dialogue box creation 7-24
Classes 7-24 Variable class 7-24 Command class 7-24 DialogueBox class 7-25 Frame class 7-25 LabelFrame class 7-25 PanedWindow class 7-25 NoteBook class 7-25 Label class 7-25 Button class 7-25 CheckButton class 7-26 RadioButton class 7-26 Entry class 7-26 List class 7-27 ComboBox class 7-27
Additional commands for all widgets 7-27
Additional commands for container widgets 7-28
Example: Internal surface creation 7-28
APPENDIX A: File Format A-1
A-1 What is STL? A-1
A-2 ’.stl’ file format specification A-1
Binary file format A-2
A-3 ’.prop’ file format specification A-2
1-1
Overview
Welcome to the HEXPRESS™ User’s Guide, a presentation of NUMECA’s fully automatic hexa-hedral grid generator. This chapter presents the basic concepts of HEXPRESS™ and shows how to get started with the program by describing:
• what is HEXPRESS
• how to use this guide,
• how to start HEXPRESS™.
1-2
Introduction
1-2.1
What is HEXPRESS™
HEXPRESSis an automatic unstructured hexahedral mesh generator software designed to auto-matically generate meshes in complex 2D and 3D geometries.
HEXPRESS generates, following a top-down revolutionary approach, meshes only containing hexahedral elements.
1-2.2
Features
The advanced unstructured code of HEXPRESS™ enables to create mesh for a large range of industrial machines designed for internal, external or turbomachinery flow.
HEXPRESS features:
—A direct interface to Parasolid™ models. HEXPRESScan automatically import Para-solid™ models involving solid bodies. The models can be visualized in wireframe and solid modes. HEXPRESSprovides simple CAD manipulations functions:
—Export a discretized computational domain to be meshed by HEXPRESSby con-verting an automatically triangulated solid bodies.
—Importation of STL models. HEXPRESScan import triangulations in colored STL for-mat. HEXPRESScreates, starting from STL files, an additional file storing a geometry attribute for each triangle of the STL triangulation. The geometry attributes allow HEX-PRESSto reconstruct topology information without the need of using sophisticated and error prone feature detection algorithms. HEXPRESSoffers merging, splitting and dele-tion funcdele-tions to manipulate and simplify triangulated models.
—Importation of CATIA models. HEXPRESS™ enables the direct importation of CATIA
v5 files (*.CATPart) up to R21, possibly including several solid bodies. Importation of CATIA v5 files is subjected to specific feature in the NUMECA license file and is only available on LINUX (64bits) and Windows (32 or 64bits) platforms.
—Mesh Wizard. HEXPRESS is organized around a very easy-to-use mesh wizard which drives the user through the various steps of the meshing process:
—Initial mesh
—Adapt to geometry
—Snap to geometry
—Optimize
—Viscous layers
—Automation. HEXPRESS has been designed for automation. User interaction is essen-tially reduced at the strict minimum. User partly interacts with adaptation step by specifying the criteria on surfaces driving the cell refinements.
—Mesh optimization. HEXPRESS implements new algorithms for mesh optimization which guarantee that a very large percentage of cells, if not all of them, are convex and of high quality (success rate if ~ 99.998% of convex cells).
—Viscous layers. HEXPRESS proposes robust high aspect ratio cell layers insertion for boundary layers resolution.
—Export. HEXPRESScan export meshes in StarCD, Fluent, Nastran, CGNS and Samcef/ Bacon compliant file format.
—Graphical User Interface. HEXPRESSinvolves a state-of-the-art graphical user inter-face with world class mesh visualization and project management functions.
1-2.3
Structured vs. Unstructured
Depending on the geometry complexity, the user should define the requested mesh type: structured or unstructured. Structured meshes are to be preferred for reasons of accuracy in cases of aligned flow even if their generation can sometimes be difficult and cumbersome. Unstructured meshes can be easily generated independently of the geometrical complexity and owing to their nature gener-ally tend to generate less points than in the structured case. For turbomachinery design, because of a request of high accuracy, it is recommended to use AutoGrid5™ which enables to provide struc-tured meshes.
Users requiring an unstructured mesh may consider the use of the NUMECA’s automatic hexahe-dral mesh generation software HEXPRESS™.
1-2.4
Approach
FIGURE 1.2.4-1 Meshing process in five steps
HEXPRESS is based on a top-down revolutionary approach. HEXPRESS involves five differ-ent steps for the meshing process.
1. Initial Mesh: HEXPRESSgenerates automatically an initial hexahedral mesh of the bound-ing box of the computational domain. The system computes an isotropic subdivision of the domain with a minimum amount of cells.
2. Adapt to Geometry: HEXPRESS successively adapts the mesh by cell anisotropic
subdivi-sion until the cell sizes match some specific geometry criteria. The adaptation criteria are either fully automated or depend on user specification:
—HEXPRESS relies on surface criteria which automatically compute cell sizes to fill nar-row gaps between surfaces with a sufficient amount of cells and refine cells locally close to high geometry curvature regions. The user can also specify his own cell size requirements.
—HEXPRESS also uses volume box refinement to refine cells in some volumes specified by the user.
—HEXPRESS removes all cells located outside the computational domain or intersecting the geometry.
3. Snap to Geometry: HEXPRESS projects the mesh on the geometry and recovers lower dimensional geometry features by some very specific corner and curve capturing. The robust-ness and accuracy of these algorithms are unique to HEXPRESS
4. Optimize: HEXPRESS optimizes the mesh to ensure that all cells are convex and of high
quality. The optimization algorithms are unique to HEXPRESS
5. Viscous Layers: HEXPRESSinserts additional layers of high aspect ratio cells in the mesh by further anisotropic cell subdivisions in order to generate a mesh suitable for resolving highly sheared flows.
1-2.5
Project Management
To manage complete mesh generation, HEXPRESS™ integrates the concept of project. An HEX-PRESS™ project involves template files and mesh files. The mesh files contains the multiblock mesh topology, geometry and grid points and the boundary condition types:
• "project_name.bcs": boundary conditions files,
• "project_name.dom": geometry files,
• "project_name.igg": template file containing all parameters used to create the mesh,
• "project_name.hex": grid points files (CGNS format),
• "project_name.hxp": extra information for the mesh generation,
• "project_name.rep": report file,
• "project_name.log": mesh generation information,
• "project_name.dist": distance file,
• "project_name.fnmb": FNMB connections,
• "project_name.qualityReport": quality report file.
These files can be loaded into the unstructured multiblock grid generation system HEXPRESS and by the CFD integrated environment FINE/Open and FINE/Marine.
To generate again an HEXPRESS™ project, the ".dom", ".bcs" and ".igg" files are necessary. They correspond to the template files.
The report file is saved at the end of the grid generation. If the new project has not yet been saved before launching the 3D generation, no report file will be saved because the system is not able to determine automatically the file location.
The quality report file is created by HEXPRESS after the optimization and viscous layers inser-tion. It stores some information about the project definition and the mesh quality criteria for the cur-rent mesh (see section 2-3.3.4 for more information).
1-3
How to Use This Manual
1-3.1
Outline
• Chapters 1and 2: introduction and description of the interface,
• Chapters 3: mesh fundamentals,
• Chapters 4 and 5: geometry definition and domain manipulation,
• Chapter 6: mesh wizard,
• Chapter 7: Python scripts.
At first time use of HEXPRESS™ it is recommended to read this first chapter carefully and cer-tainly section 1-4 to section 1-6. Chapter 2 and Chapter 3 give a general overview of the HEX-PRESS™ interface and the way to manage a project. Chapter 4 and Chapter 5 give information on how to prepare a domain for the mesh generation. For every mesh generation, the input parameters can be defined as described in the Chapter 6.
1-3.2
Conventions
Some conventions are used to ease information access throughout this guide:
• Commands to type in are in italics.
• Keys to press are in italics and surrounded by <> (e.g.: press <Ctrl>).
• Names of menu or sub-menu items are in bold.
• Names of buttons that appear in dialog boxes are in italic.
• Numbered sentences are steps to follow to complete a task. Sentences that follow a step and are preceded with a dot (•) are substeps; they describe in detail how to accomplish the step.
The hand indicates an important note.
The pair of scissors indicates a keyboard shortcut.A light bulb in the margin indicates a section with a description of expert parameters.
1-4
First Time Use
1-4.1
Basic Installation
First of all, HEXPRESS™ should be properly installed according to the installation note. The installation note provided with the software should be read carefully and the following points are specifically important:
• Hardware and operating system requirements should be verified to see whether the chosen machine is supported.
• Installation of HEXPRESS™ according to the described procedure in a directory chosen by the user and referenced in the installation note as ‘NUMECA_INSTALLATION_DIRECTORY’.
• A license should be requested that allows for the use of HEXPRESS™ and the desired compo-nent and modules (see section 1-6 for all available licenses). The license should be installed according to the described procedure in the installation note.
• Each user willing to use HEXPRESS™ or any other NUMECA software must perform a user configuration as described in the installation note.
When these points are checked the software can be started as described in the installation note or section 1-5 of this users guide.
1-4.2
Expert Graphics Options
1-4.2.1 Graphics Driver
The Graphics area of HEXPRESS™ interface uses by default an OPENGL driver that takes advan-tage of the available graphics card. When the activation of OPENGL is causing problems, HEX-PRESS™ uses an X11 driver (on UNIX) or MSW driver (for Windows) instead.
It is possible to explicitly change the driver used by HEXPRESS™ in the following ways: On UNIX: in csh, tcsh or bash shell: setenv NI_DRIVER X11 in korn shell: NI_DRIVER=X11 export NI_DRIVER
The selection will take effect at the next session. On Windows:
• Log in as Administrator.
• Launch regedit from the Start/Run menu.
• Go to the HKEY_LOCAL_MACHINE/SOFTWARE/NUMECA International/Hexpress31_# or HKEY_LOCAL_MACHINE/SOFTWARE/NUMECA International/FineOpen31_# or HKEY_LOCAL_MACHINE/SOFTWARE/NUMECA International/FineMarine31_# register.
• Modify or add (right-click & New/String Value) the DRIVER entry to either OPENGL or MSW.
The selection will take effect at the next session.
1-5
How to Start HEXPRESS™ Interface
In order to run HEXPRESS™ standalone version, the following command should be executed:
• On UNIX and LINUX platforms type: hexpress -niversion 31_# <Enter> or hexpress31_#
<Enter>
In order to use HEXPRESS™ included in FINE™/Marine or FINE™/Open package, "31_#" should be replaced by "marine31_#" or "open31_#".
• On Windows click on the HEXPRESS icon in Start/Programs/NUMECA software/
Hexpress31_#/ or Start/Programs/NUMECA software/FineOpen31_#/ or Start/Programs/ NUMECA software/FineMarine31_#/. Alternatively HEXPRESS™ (32bits) can be launched
from a Dos shell by typing:
<NUMECA_INSTALLATION_DIRECTORY>\Hexpress31_#\bin\hexpress.exe <Enter> or <NUMECA_INSTALLATION_DIRECTORY>\FineOpen31_#\bin\hexpress.exe <Enter> or
<NUMECA_INSTALLATION_DIRECTORY>\FineMarine31_#\bin\hexpress.exe <Enter>.
where NUMECA_INSTALLATION_DIRECTORY is the directory indicated in section 1-4.1. And HEXPRESS™ (64bits) can be launched from a Dos shell by typing:
<NUMECA_INSTALLATION_DIRECTORY>\Hexpress31_#\bin64\hexpressx86_64.exe <Enter> or <NUMECA_INSTALLATION_DIRECTORY>\FineOpen31_#\bin64\hexpressx86_64.exe <Enter> or <NUMECA_INSTALLATION_DIRECTORY>\FineMarine31_#\bin64\hexpressx86_64.exe <Enter>.
where NUMECA_INSTALLATION_DIRECTORY is the directory indicated in section 1-4.1.
1-6
Required Licenses
1-6.1
Standard HEXPRESS™ License
The standard license for HEXPRESS™ allows for the use of all basic features of HEXPRESS™ includ-ing:
• CAD importation and geometry management (except CATIA v5),
• multi-domain capability and FNMB connections,
• mesh periodicity and rotor/stator capabilities.
1-6.2
Additional Licenses
Next to HEXPRESS™ other products are available and require separate licenses:
• FINE™/Turbo (structured mesh generator - solver - visualization software) dedicated to turboma-chinery applications,
• FINE™/Design 3D (3D inverse design) dedicated to design,
• IGG™ (structured mesh generator),
• AutoGrid5™ (automatic structured mesh generator for turbomachinery),
• HEXPRESS™/Hybrid (unstructured mesh generator),
• FINE™/Open (unstructured mesh generator - solver - visualization software) dedicated to aerody-namics and turbomachinery applications,
• FINE™/Marine (unstructured mesh generator - solver - visualization software) dedicated to marine applications.
2-1
Overview
This section describes the appearance and use of the HEXPRESS Graphical User Interface (GUI).
FIGURE 2.1.0-1 HEXPRESS™ Interface
The HEXPRESS GUI is divided into several main components as shown in Figure 2.1.0-2:
• Menu bar
• Quick Access Pad
• Control area
• Graphics area
FIGURE 2.1.0-2 HEXPRESS GUI
The following sections describe these components as well as one additional important features: keyboard shortcuts.
2-2
Welcome Dialog Box
The welcome dialog box (Figure2.2.0-1) is displayed at start-up or when the Project/New menu is selected or when the Toolbar/New button ( ) is pressed. Several choices are available to the user:
—Open an existing HEXPRESS, HEXPRESS/Hybrid, IGG or AutoGrid5 project, i.e. a file with extension ".igg". Please refer to section 2-3.1.2 on page 2-4 for more details.
—Import a valid computational domain, i.e. a file with extension ".dom". Please refer to sec-tion on page 4-3.
—Import a ".dat" file. Please refer to section 2-3.1.5 on page 2-8 for more details.
Current project name
Keyboard input areaMessage area Viewing buttons
Grid parameters area Mouse coordinates Information area
Graphics Area
Quick Access Pad
Control Area Menu Bar
—Import a Stereo Lithography Triangulation (STL), i.e. a file with extension ".stl". Please refer to section 4-3 on page 4-20.
—Import a CAD model in Parasolid™ format, i.e. a file with extension ".xt" or ".xt_txt". Please refer to section 4-2 on page 4-4.
—Import ANSYS mesh (see 8)
—Import CGNS mesh (see 8)
—Execute a python script
—Quit to exit HEXPRESS
FIGURE 2.2.0-1 Welcome to HEXPRESS dialog box
2-3
Menu Bar
The menu bar contains several menus which can be activated using mouse click and drag or mouse click and release modes.
This section describes all available menus:
• Project, • Internal Surface, • Grid, • View, • STL, • Tools, • Plugins.
2-3.1
Project Menu
2-3.1.1 Project/New
Project/New closes the current project and opens up the HEXPRESSwelcome dialog box. The old project is not automatically saved before being closed. Therefore, be sure that the current work is saved before using this option. All system parameters are reset to their default values and a new 3D project is initialized. All curves and surfaces are removed from the working memory.
2-3.1.2 Project/Open
Project/Open is used to open an existing project, previously created by HEXPRESS. A file chooser window (Figure2.3.1-1) is opened to enable selection of an existing HEXPRESS project file with an ".igg" extension.
FIGURE 2.3.1-1 HEXPRESS project file chooser
Upon selection of a valid project, HEXPRESS closes the current project and opens the new one. The old project is not automatically saved before being closed. Therefore, be sure that the current work is saved before this option is used.
An unstructured project from HEXPRESS™/Hybrid or a multiblock structured project from IGG™ or AutoGrid5™ can also be loaded into HEXPRESS.
a) Structured project for turbomachinery applications
HEXPRESSautomatically converts the multiblock structured mesh into an unstructured hexahe-dral mesh in HEXPRESS format. Upon importing the structured mesh, the user is given the choice to keep or remove all the Non matching connections (NMB), Periodic matching connections (PER) and Periodic non matching connections (PERNM) before converting it into HEXPRESS format. See Figure2.3.1-2. By default all the connections will be kept.
FIGURE 2.3.1-2 Dialogue shown upon loading a structured mesh for turbomachinery applications
User is also allowed to convert the structured mesh with the desired multigrid level through mesh converter dialog box. If the option Keep finest grid only is activated, it saves the project by keep-ing the finest grid only.
FIGURE 2.3.1-3 Mesh converter dialog box
The user is then requested to specify a new project name for the converted project. The converter defines a new HEXPRESS computational domain by triangulating the surfaces of the quadrilat-eral multiblock grid. Boundary conditions are exported into the new HEXPRESS project. All blocks connected by matching mesh faces (CON boundary condition) are concatenated to define single computational domain.
When the multiblock structured project from IGG™ contains a butterfly mesh, it has to be split inside IGG™ before loading into HEXPRESS.
When the structured project from IGG™ or AutoGrid5™ contains undefined patches (UND), they have to be changed in another type (for example CON if at the connection between blocks) before loading into HEXPRESS™ otherwise the concerned patches will be considered as an internal surface in the converted mesh.b) Structured project for marine applications
HEXPRESSautomatically converts the multiblock structured mesh into an unstructured hexahe-dral mesh in HEXPRESS format. Upon importing the structured mesh, a pop-up message shown in Figure2.3.1-4 appears for user to confirm the conversion. The user is then requested to specify a new project name for the converted project and the desired multigrid level through the mesh con-verter dialog box shown in Figure
FIGURE 2.3.1-4 Confirmation dialogue to load a structured mesh
FIGURE 2.3.1-5 Mesh converter for marine applications
The converter defines a new HEXPRESS computational domain by triangulating the surfaces of the quadrilateral multiblock grid. Boundary conditions are exported into the new HEXPRESS project. The inlet (INL) and outlet (OUT) patches will be converted automatically into external (EXT) patches. In case some rotor-stator connections (ROT) are found in the project, a warning as shown in Figure2.3.1-6 is issued. These connections will be converted into simple FNMB connec-tions (SOL*).
FIGURE 2.3.1-6 Warning about the rotor-stator connections in the mesh
2-3.1.3 Project/Save
Project/Save saves the current project. When saving for the first time, a new file name must be
specified, through a file chooser, by the user with the extension ".igg". The saving procedure writes information in the following files:
FIGURE 2.3.1-7 Project files
• "project_name.bcs": boundary conditions files,
• "project_name.dom": geometry files,
• "project_name.igg": template file containing all parameters used to create the mesh,
• "project_name.hex": grid points files (CGNS format) including the information about cells belonging to the viscous layers,
• "project_name.hxp": extra information for the mesh generation,
• "project_name.rep": report file,
• "project_name.log": mesh generation information,
• "project_name.dist": distance file,
• "project_name.nmb": NMB, PER and PERNM connections,
• "project_name.fnmb": FNMB connections,
• "project_name.qualityReport": quality report file.
Thanks to the files stored in the folder called "cache", the user can come back to whichever inter-mediate step without starting the mesh generation again from the beginning:
• "project_name_step.hex" (or ".hxp"): grid points file (CGNS format) after a step between init,
adapt, snap or regularize corresponding to Initial, Adaptation, Snapping and Optimization step
respectively.
• "project_name_step.fnmb": FNMB connections file after a step between init, adapt, snap or
regularize corresponding to Initial, Adaptation, Snapping and Optimization step respectively.
The files stored in the "cache" folder can be removed when the project is over and they are not needed to generate the mesh again. To remove them, please read chapter 2-3.1.7.2-3.1.4 Project/Save as...
Project/Save as saves an existing HEXPRESS project under a user defined name. Different grids created by using the same boundary data can be saved separately for further comparison.
FIGURE 2.3.1-8 Project / Save as...
2-3.1.5 Project/Import...
Following files can be imported:a) Project/Import.../Project
Project/Import.../Project reads an external mesh file ".igg". Several mesh files can be opened.
This enables multiblock computations within FINE™/Open or FINE™/Marine.
b) Project/Import.../Domain
Project/Import.../Domain reads an external geometry domain file ".dom". Several domains files
can be opened. This enables multiblock computations within FINE™/Open or FINE™/Marine.
c) Project/Import.../.dat
Project/Import.../.dat reads external geometry files in ".dat" format. 2D domain creation is
possi-ble by importing the ".dat" file containing complete curve definitions of the 2D geometry or only wire curves.
Upon importing the file, HEXPRESS™ switches to 2D mode automatically. The imported curves will be put in XY view and adjusted to full view. In the CAD Manipulation subpanel (Figure 2.3.1-9), the user has the possibility to create polylines, csplines and arcs. With these options, it is possi-ble to create a closed contour or bounding box from the imported wire curves.
FIGURE 2.3.1-9 2D CAD Manipulation subpanel
As soon as a closed contour is formed, by clicking on the Create 2D Domain button, the dialog box shown in Figure2.3.1-10 appears for the user to specify the domain size in Z direction. Upon click-ing on the Create button, the domain can be saved as ".dom" file under user-defined name
FIGURE 2.3.1-10 Create 2D Domain for ".dat" file
The file format must be correct. Otherwise, HEXPRESS™ issues an error message like "invalid file format or corrupted file!".
Curves in the file should form a closed contour without gaps or self intersections at the stage of domain creation. This contour should be placed on one of the three Cartesian planes. The maximum valid gap size between two adjacent curves is 0.5% of the size of the smallest curve. If this restriction is not satisfied, HEXPRESS™ issues an error mes-sage.
The height of the 2D domain is positive always. Its minimum value is 10e-4. The ".dat" file should have the following format:—The first line is the header.
—The header is followed by the list of curves.
—Definition of each curve consists of:
- the curve format (XYZ or ZR) and the type of curve (polyline or cspline only) - the number of points.
- the list of points in appropriate format as defined in the curve format and type.
d) Project/Import.../Parasolid
Project/Import.../Parasolid reads external geometry files in Parasolid™ format ".x_t". Several
Parasolid™ files (Parasolid™ and CATIA v5) can be opened when defining the geometry before the domain creation. Versions up to 26.0 are supported.
2D domain creation is also possible by importing the Parasolid™ file containing only wire entities. Upon importing the file, HEXPRESS™ switches to 2D mode automatically. The imported curves will be put in XY view and adjusted to full view.
The user has the possibility to create polylines, csplines and arcs in the CAD Manipulation sub-panel (Figure2.3.1-9). With these options, it is possible to create a closed contour or bounding box from the imported wire entities.
Upon clicking the Create 2D Domain button, a dialog box shown in Figure 2.3.1-11 appears. The default value for each discretization parameter is computed automatically by HEXPRESS™. How-ever, the discretization resolution of the domain can be modified by the user.
• Maximum length: the maximum edge length of the triangulation facets. The smaller the value, the denser the discretization.
• Curve chordal tolerance: the maximum distance between a curve and the corresponding triangu-lation edges. The smaller the value, the denser the discretization.
• Curve resolution: the maximum angle (in degrees) between a curve and the triangulation edges. The values may range from 1.0 to 30. The smaller the value the denser the discretization. By clicking on the Apply button, the discretization of the selected geometry with the values speci-fied for each parameter is updated in the graphics area. By clicking on the Default button, the value for the associated parameter will be reset to the default one.
It is also possible for the user to modify the domain size in Z direction for 2D domain creation. Upon clicking on the Create button, the domain can be saved as ".dom" file under user-defined name.
FIGURE 2.3.1-11 Create 2D Domain for Parasolid™ files
The discretization parameters are positive always. If the value specified is zero, it means no limitation is imposed on this parameter.
The limitations mentioned for ".dat" file import apply for Parasolid™ import. See sec-tion c) on page 2-8.e) Project/Import.../STL triangulation
Project/Import.../STL triangulation reads external geometry files in STL format ".stl". Several
STL files can be opened when defining the geometry before the domain creation.
HEXPRESS™ also supports colored STL formats.f) Project/Import.../CATIA v5 model
Project/Import.../CATIA v5 model reads external geometry files in CATIA format ".CATPart".
Several Parasolid™ files (Parasolid™ and CATIA v5) can be opened when defining the geometry before the domain creation. Versions up to R23 are supported.
g) Project/Import.../ANSYS mesh
Project/Import.../ANSYS mesh reads external mesh files in ANSYS format ".cdb" v8.0.
h) Project/Import.../CGNS mesh
Project/Import.../CGNS mesh reads unstructured 3D mesh stored in a CGNS format and converts
it to its native mesh format. The input mesh is not necessary pure hexahedral, i.e. it might contain tetrahedron, prism, pyramid cells and can contain hanging nodes.
When converting the mesh, the boundary conditions will be recovered and corresponding HEX-PRESS™ boundary conditions will be set. In addition for pure hexahedral input meshes, the opti-mization and the viscous layer insertion can be performed in HEXPRESS™ on these meshes.
The option does not import CGNS mesh including multiple blocks. It only imports single block mesh.i) Project/Import.../HEXPRESS/Hybrid mesh
Project/Import.../HEXPRESS/Hybrid mesh allows to read unstructured volume meshes created
by HEXPRESS™/Hybrid and saved in HEX format.
Before loading the mesh in HEXPRESS™, the boundary conditions have to be defined in HEXPRESS™/Hybrid.2-3.1.6 Project/Export
a) Project/Export.../StarCD
The StarCD export functionality is available to the user via menu Project/Export.../StarCD. Four files are saved in the directory and with the project name specified by the user through a file chooser:
—’project_name.cel’ contains the cells definition in terms of nodes
—’project_name.vrt’ contains the coordinates of the vertices
—’project_name.cpl’ contains the coupling definitions between cells through faces presenting hanging nodes (Figure
2.3.1-12)
—’project_name.bnd’ contains the list of boundary faces with boundary condition information
FIGURE 2.3.1-12 Definition of hanging node at cells connection
Exporting multiblock domains is not available in StarCD format.The StarCD file format output by HEXPRESS complies with the STARCD User Guide, Version 3.05, 1998. For STARCCM+ users, it is mandatory to use the "ngeom" command to convert mesh data from STARCD to STARCCM+. This tool is provided in the STARCD package v3.26.
• The file "project_name.cel" stores the connectivity between the cells and the nodes. Figure2.3.1-13 presents the connectivity of the NUMECA and StarCD hexahedron cell.
FIGURE 2.3.1-13 StarCD, HEXPRESS hexahedra
The connectivity file is written using the following FORTRAN ASCII format: I9 6X 9I9 1X I4
Cell number, eight vertices, cell type number, cell key where:
—cell type number is the region of the cell. HEXPRESS currently outputs all cells in the same region with index 1.
—cell key defines the type of the cell:
1. Fluid cell 2. Solid cell 3. Baffle 4. Shell 5. Line 6. Point
All cells currently exported by HEXPRESS are fluid cells (cell key is equal to 1).
• The file "project_name.vrt" stores the nodes coordinates which are exported with the following FORTRAN format:
I9 6X 3G16.9
Vertex number, three coordinates
• The file "project_name.bnd" stores the list of boundary facets. A boundary in StarCD is a mesh facet connected to a geometry surface. Boundaries are grouped in regions. Boundary mesh fac-ets are exported with the following FORTRAN format statement:
I8 6X 4I9 2I7 A
Boundary number, four vertices, region number, patch number, region type, (characters)
where:
—The region number corresponds to the ID of a topological face of the HEXPRESScompu-tational domain.
—The region type defines the type of boundary condition. HEXPRESS exports the follow-ing StarCD boundary condition:
INLE: inlet OUTL: outlet WALL: wall
• The cell to cell connection referred to as “couple” in StarCD defines the transition between coarse and fine mesh cells with hanging nodes. A couple allows the faces of several (small) cell slaves to be connected to one master (large face). Couples are exported with the following FOR-TRAN format in the file "project_name.cpl":
I8 1X I5 1X I8/7(I9,I2)
Couple number, number of cells, type of coupling, CELL1, FACE1, CELL2, FACE2....
where:
—The type of coupling is set to 1 by default in 3D
—CELL1: the index of the master cell
—CELL2: the index of a slave cell
—FACE1, FACE2: the number of the face in the cell (0->5)
b) Project/Export.../Fluent
This Fluent export functionality is available to the user via menu Project/Export.../Fluent. An ASCII file is saved in the directory and with the project name specified by the user as "project_name.msh". The format of this exportation complies with Fluent 6.3.
A Fluent mesh file contains certain partitions of information called zones. Each zone is a separate block that contains information about objects of one type: faces, cells, nodes, hierarchy tree, com-ments, etc. Each zone must be enclosed in parentheses.
The content of a zone depends on the particular type of the zone. Each zone has an ID needed for successful referencing the information stored in the zone. Each zone has a header including general information related to the zone: initial and final indices of the elements described in the zone, com-ment text, etc. This header must be enclosed in parentheses as well. The header of a zone of a cer-tain type must be followed by the zone body. It includes detailed information about the mesh objects described in the zone. The body must be enclosed in parentheses. Zones may be either optional or required (zones 0, 1 and 2 are optional, all other zones are required). Below is a short description of the zone types that are used for exportation by HEXPRESS
TABLE 1. Fluent format zone types used by HEXPRESS
Index Name Description
0 Comment Comments for blocks of the file
1 Header Information about the code that wrote the file 2 Dimensions Dimensionality
10 Nodes The total number of nodes in the mesh or the coordinates of the mesh nodes
12 Cells The total number of cells in the mesh or the number of cells of a certain type
Remarks:
1. The mesh generation strategy of Fluent is essentially conformal. Non-conformity is the result of mesh adaptation by the Fluent flow solver. HEXPRESS exports only leaf cells1 on finest level to the
Flu-ent file, because the cell hierarchy supported in HEXPRESS cannot be correctly described in terms of the Fluent mesh file format. Face hierarchy is preserved only partially. As only leaf cells are exported, only their faces must be exported in order to preserve consistency between cells and faces (only faces or nodes referenced by leaf cells must be exported). Thus, the face hierarchy is preserved for exported faces only: if one leaf cell references a face and another one references its child face (generated face), then the parent-child dependency is exported to a Fluent file.
2. Fluent mesh generator does not officially support anisotropic refinement. HEXPRESS, on the
con-trary, is able to generate fully or partially anisotropic meshes. Fluent flow solver however accepts meshes that contain anisotropicity and behaves properly during computations. However, it is not rec-ommended to perform a mesh check (via Fluent’s menu Grid/Check) because it will result in multi-ple warnings reporting incorrect number of child faces encountered in zones with index 59.
3. As ASCII mode is used to export file into FLUENT format, the floating point values such as coordi-nates of mesh nodes should be written in a fixed format with a certain fixed number of digits after decimal point. The current version supports exportation with 12 digits, unlike version 1.1 where only 6 digits were written.
The table below lists the dependency between Fluent and HEXPRESS boundary condition types. Any of the Fluent boundary conditions is applied by selecting the appropriate boundary condition type of HEXPRESS. The correspondence is not unique because of the large number of boundary conditions available in Fluent. Moreover, groups and set up of boundary conditions are also exported to Fluent.
HEXPRESS™ type Fluent type ID Fluent type description
EXT 9 pressure-far-field INL 10 velocity-inlet OUT 36 outflow MIR 7 symmetry
PER 12 or 8 periodic or periodic-shadow SOL 3 wall
ROT 4 or 5 (or 3) pressure-inlet or pressure-outlet (or wall)
For patches defining rotor-stator, they will be exported as "pressure-inlet", "pressure-outlet" or "wall" if their name is respectively containing the keyword "inlet_rotor-stator", "outlet_rotor-stator" or none of the previous keywords.
When periodic (PER) boundary conditions are set into HEXPRESS™ and the mesh exported to Fluent, there is an access violation error when building the grid. The workaround is to switch PER to mirror (MIR) boundary condition, then export and rework in Fluent.13 Faces The total number of faces in the mesh or full information about mesh faces - nodes and adja-cent cells
59 Face tree Parent-to-child dependency among mesh faces
Fluent format zone types used by HEXPRESS Index Name Description
The FNMB concept does not exist in Fluent. FNMB created in HEXPRESS™ are thus ignored.
Fluent may present poor results at the periodic boundary conditions but its get better the finer (better resolution) the mesh is at the periodic connection.
The quality of all HEXPRESS™ mesh files exported to Fluent (with suffix) ".msh" cannot be checked in T-GRID. Nevertheless, the check is possible directly in Fluent: /Grid/Check.
Files with suffix ".msh" must be imported in Fluent 6.0 (or more) rather than simply opened like in Fluent 5.3 and 5.4.
Fluent 6.0 then automatically performs checks on the imported mesh and typically displays a set of warnings referring to the presence of anisotropic subdivisions in the mesh as explained in the above mentioned remark. These warnings are indicative and have not been reported to hinder the conver-gence or the accuracy of the simulation.
c) Project/Export.../Samcef-Bacon
HEXPRESS exports conformal hexahedral meshes in the Samcef/Bacon ASCII mesh file format. This option is available to the user via menu Project/Export.../Samcef-Bacon. An ASCII file is exported in the user-defined directory and denoted "project_name.bacon".
Exporting multiblock domains is not available in Samcef-Bacon format.The file contains a region defining the node coordinates. The region starts by a tag .NOE, then each node is listed with the following format:
I node index X x y z
The cell connectivity is exported in a region beginning with the tag .MAI. Cells are listed as fol-lows:
I cell index N n1 n2 n3 n4 0 n5 n6 n7 n8
The following correspondence exists between the NUMECA hexahedron (see Table 2) numbering and the Samcef/Bacon one:
This file format is only compatible with fully conformal meshes (mesh presenting no hanging nodes - see Figure
2.3.1-12).
TABLE 2. NUMECA-Samcef/Bacon hexahedron nodal numbering
HEXPRESS Samcef/Bacon 0 0 1 1 2 2 3 3 4 5 5 4 6 7 7 6
d) Project/Export.../CGNS
The menu Project/Export…/CGNS offers the possibility to export meshes generated by HEX-PRESS in standard CGNS format. The CGNS file will contain coordinates of mesh vertices, cell connectivity, parent-child information of mesh faces and edges, boundary faces connectivity and boundary conditions.
The CFD General Notation System (CGNS) provides a general, portable, and extensible standard for the storage and retrieval of computational fluid dynamics (CFD) analysis data. It consists of a collection of conventions, and free and open software implementing those conventions.
The CGNS system is designed to facilitate the exchange of data between sites and applications, and to help stabilize the archiving of aerodynamic data. The data are stored in a compact, binary format and are accessible through a complete and extensible library of functions.
The finest mesh for all domains will be exported and the following data will be stored in the file:
• Coordinates of nodes
• Connectivity of cells
• Connectivity of cell faces on the boundary (surface mesh)
• Boundary conditions
General information such as file structure on CGNS web site: www.cgns.org
The CGNS file will contain one base. The name of this base is “Unstructured data”. The base will be divided into zones. One zone corresponds to one domain. Here is the description of each zone:
• Zone type: Unstructured
• Zone name: name of the domain
—Vertex coordinates
Only the finest grid is considered. The vertex Cartesian coordinates are stored under the node ‘GridCoordinates_t’. The names of each component are respectively “CoordinateX”, “Coordi-nateY”, and “CoordinateZ”.
—Cell connectivity
The cell connectivity is stored under the node ‘Elements_t’. All the cells generated by HEX-PRESS are hexahedral, with no internal vertex, so the CGNS cell type ‘HEXA_8’ has been cho-sen to define them. Moreover the cell connectivity definition in HEXPRESS differs from the CGNS definition:
FIGURE 2.3.1-14 HEXPRESS (left picture) and CGNS (right picture) connectivities
—Face cell connectivity on the boundary
The boundary elements are separately listed in the CGNS file. This is useful for assigning boundary conditions.
So there are as many additional ‘Elements_t’ nodes as topological surfaces. Each of these addi-tional nodes lists the corresponding faces as elements, which CGNS type is ‘QUAD_4’.
—Boundary conditions
The boundary conditions are stored under the node ‘BC_t’. The name of this node is the name of the BCData.
The boundary conditions can be applied either on nodes, either on boundary faces. Here, each boundary condition is defined by a list of boundary elements. The lists have been defined previ-ously in the “Face cell connectivity on the boundary” section.
The boundary condition type is set for each boundary element. Here is the correspondence between CGNS and HEXPRESS boundary condition types:
e) Project/Export.../NASTRAN
HEXPRESScan export mesh files to NASTRAN format (".bdf") in single or double precision (the choice is asked during exportation). The selection between single and double precision is done after clicking on Nastran menu.
FIGURE 2.3.1-15 Precision for Nastran export
f) Project/Export.../OpenFOAM
The mesh is converted into polymesh representation accepted by OpenFOAM1. The latter is based around faces. Internal cells connect 2 cells. Boundary faces address a cell and a boundary patch. Each face is assigned an ‘owner’ cell and ‘neighbour’ cell so that the connectivity across a given face can simply be described by the owner and neighbour cell labels. In the case of boundaries, the
TABLE 3. CGNS/HEXPRESS correspondence
CGNS designation HEXPRESSdesignation
BCExtrapolate EXTERNAL
BCInflow INLET
BCSymmetryPlane MIRROR BCOutflow OUTLET
BCWall SOLID
1. [1] OpenFOAM , User Guide , Version 1.6 , 2009 and [2] OpenFOAM , Programmer’s Guide, Version 1.6 , 2009.
connected cell is the owner and the neighbour is assigned the label ‘-1’. The I/O specification con-sists of the following files:
1) points a list of vectors describing the cell vertices, where the first vector in the list represents ver-tex 0, the second vector represents verver-tex 1, etc.;
2) faces a list of faces, each face being a list of indices to vertices in the points list, where, the first entry in the list represents face 0, etc.;
3) owner a list of owner cell labels, the index of entry relating directly to the index of the face, so that the first entry in the list is the owner label for face 0, the second entry is the owner label for face 1, etc;
4) neighbour a list of neighbour cell labels;
5) boundary a list of patches, containing a dictionary entry for each patch, declared using the patch name.
To know how many cells are in their domain, there is a note in the FoamFile header of the owner file that contains an entry for nCells.
When exporting an imported structured mesh (converted in unstructured) only the finest grid level is supported. It is not possible to export in OpenFOAM a coarser grid level.g) Project/Export.../CEDRE
HEXPRESScan export mesh files to CEDRE format (".dat" and "_bcs.dat"). The file is com-posed by five sections including generality, node coordinates, connectivity: faces to nodes, connec-tivity: face to cells and marked faces (for boundary conditions).
Full Non Matching connections (FNMB) are not supported by CEDRE.h) Project/Export.../CEDRE (short names)
HEXPRESScan export mesh files to CEDRE format (".dat" and "_bcs.dat"). The file is com-posed by five sections including generality, node coordinates, connectivity: faces to nodes, connec-tivity: face to cells and marked faces (for boundary conditions). In both files, the face names are automatically adapted to maximum 13 characters.
Full Non Matching connections (FNMB) are not supported by CEDRE.2-3.1.7 Project/Clear cache...
The menu Project/Clear cache... offers the possibility to clear the mesh stored in the cache sub-folder after each generation step is completed or at the end of a mesh generation for instance. This can free a significant disk space but will no longer allow to re-load a previous step from the mesh wizard.
2-3.1.8 Project/Script...
Actions executed by the user through the HEXPRESS™ interface are recorded in a Python-like script giving added flexibility for automation of geometry creation and mesh generation.
Project/Script.../Edit... opens a dialog box displaying all the commands performed by the user
since the beginning of its session. The user can easily edit this script (add, remove and modify com-mands). The dialog box contains two pull-down menus. File menu allows to open a script in a sepa-rate dialog box and to save the script in a file. Run menu allows to run the script shown in the window under the current session ("Rerun on top").
FIGURE 2.3.1-16 Script Recording
Project/Script.../Save All... is used to save the dynamic recording of all commands performed by
the user since the beginning of its session.
Project/Script.../Execute... is used to run a python script file containing HEXPRESS™
com-mands. A file chooser is opened to select a file with a ".py" extension. Upon selection of a valid file, the script is executed in the current session and the result is visualized in the graphical window. Depending on the content of the script, operations will be added to the current project or a new project will be automatically opened before operations are performed (the previous project is closed). If the script being run contains a syntactical error it will be aborted and a message will appear in the shell.
Project/Script.../Re-execute Last can be used to rerun the last script that was run using the Project/Script.../Execute... command. This option is most useful when writing own scripts
manu-ally to rapidly test it on the fly.
2-3.1.9 Project/Print/As PNG
Project/Print/As PNG is used to specify a file name in which a snapshot of the graphical area is
saved as a PNG formatted picture. A file chooser is opened and when a valid file name is selected, click on Ok to perform the picture output.
2-3.1.10 Project/Preferences...
Graphic tab gives choices for the graphics driver.
Only drivers (X11 and/or OPEN_GL) usable on the platform are present.FIGURE 2.3.1-17 Project / Preferences... - Graphics
Mesh generation tab allows expert users to modify the memory allocation and the preference for
multigrid level.
• Chunksize. The default memory value is set to 40,000 (no units) and usually is unchanged. It
specifies the amount of memory to reserve (pre-allocation) before complex object initialization. If this amount of memory is too small, the memory will be over-fragmented, and we can reach a bottleneck. At the contrary, if it is too large, there won't be memory limitation, but the software will be slower. There is no specific recommendation about the value to set, it depends on the size of the generated mesh.
Suggestion: increase the chunksize by 150,000 until the software can allocate all the necessary memory. For information, the chunksize has been set to 700,000 to allocate 3.5 Gb on a SGI platform.FIGURE 2.3.1-18 Project / Preferences... - Mesh generation
Loading tab allows users to choose if they want to load the mesh when opening the project or not.
FIGURE 2.3.1-19 Project / Preferences... - Loading
By default this parameter is not activated, i.e. mesh will not be loaded. The mesh will be loaded automatically when actions requiring manipulations of mesh are activated. For instances:
• Mesh visualization using the mesh icon
• All mesh cutting tools
• Cell viewer
• All mesh export options
• All mesh quality check options
• Mesh transformation
• FNMB computation
• Delete block option
• Multiblock option
—If a mesh generation step of one block is done/undone (e.g. executing a mesh generation step or deleting the previous step), the whole mesh will be reloaded first. This is mandatory since when saving the project, the whole .hex file containing the mesh of each block, needs to be rewritten.
The message shown in Figure2.3.1-20 appears at bottom left of the GUI when a project is loaded in HEXPRESS.
FIGURE 2.3.1-20 Message shown upon loading a project
When executing python scripts or opening a project in batch mode, the mesh is always loaded.2-3.1.11 Project/Quit
Project/Quit ends the interactive session. A dialog box opens up to confirm the end of the session.
Please notice that the current work is not automatically saved when exiting HEXPRESS.
FIGURE 2.3.1-21 Project/Quit
Press <Ctrl-q> to directly access this menu item.2-3.2
Internal Surface
Basic geometrical operations are available in HEXPRESS™, with the objective to create/edit/delete internal surfaces and allow subsequent local mesh refinement nearby these surfaces during the adaptation step (see chapter 6). These operations are not dedicated to geometry creation and thus, we suggest using CAD software. The options proposed are identical to the ones available in IGG™ and can be reached within the menu Internal Surface and the Quick Access Pad/Internal Surface access.
2-3.2.1 Internal Surface/Edit
Several operations can be performed for editing. This includes copy, translation, rotation, scaling and mirroring of existing entities. Conversion to C-spline can also be accessed.
a) Edit->Copy
Internal Surface/Edit /Copy is used to create new curves and surfaces by cloning the selected
geometry curves and surfaces.
After the cloning, new entities can be transformed directly through this tool: Translation(t), Rotation(r), Scale(s), Mirror(m), None(q)
To perform a simple copy, enter <q> and press <Enter>. Other operations are strictly equivalent to the corresponding ones of the Edit menu.
After the cloning, all currently selected geometry entities are unselected and the new created enti-ties are selected. This allows to perform other editing operations on these entienti-ties without having to manually select them.
b) Edit->Translate
Internal Surface/Edit /Translate is used to translate all the selected geometry entities (curves and
surfaces) along a user-defined vector. The following prompt is given to specify the translation vec-tor:
Translation vector (q)
