Sin descomposición 728,70
8.3 RED SEMAFÓRICA
HEXPRESS proposes a very specific approach for the insertion of layers of large aspect ratio cells to accurately resolve boundary layers. The technique is based on successive subdivisions of the cells connected to the walls, this contrasts with other techniques which insert layers by extru- sion. This refinement technique has the advantage of robustness and speed. Besides, the inflation algorithm improves the mesh quality in viscous layers.
3-4
Mesh Quality
After the grid generation, the menu Grid/Mesh Quality... computes and displays per block the characteristics of the mesh in terms of negative or concave cells and of minimum-maximum of the cells volume, the aspect ratio and the cells skewness. More details in section 2-3.3.4 on page 2-45.
3-5
Multi-Domain
The introduction of multi-domain option largely enhance HEXPRESS™ capabilities, with the pos- sibility to import and manage several domains and meshes in the same project. Furthermore it allows to merge meshes exported from HEXPRESS™/Hybrid, IGG™ and AutoGrid5™ (structured NUMECA mesh generators) with HEXPRESS™ domains as illustrated in Figure3.5.0-1.
FIGURE 3.5.0-1 Multi-domain
When dealing with a multi-domain project, several "water-tight" computational domains (".dom") have to be loaded within HEXPRESS™ through the menu /Project/Import.../Domain. When the domains are imported, their selection is performed by left-clicking on it in the graphic area or by the
Active block entry in the tool bar.
Domain manipulations (section 2-5.3 on page 2-86) if necessary have to be performed before mesh generation.When generating the mesh following the wizard (section 3-3 on page 3-4), all settings and viewing operations are applied separately to each domain after selecting it in Active block in the Toolbar or by left-clicking on it.
When HEXPRESS™ meshes are generated based on each imported domain, addi- tional existing structured or unstructured meshes can be added into the project through the menu Project/Import.../Project.Finally before saving the whole project, connections between generated and/or imported meshes have to be specified through the menu Grid/Non Matching Connections.... This menu allows to specify a user-defined connection between meshes. Two types of connection can be defined: full non matching connection and rotor/stator connection. The last type, in practice, allows to connect two domains presenting different periodicity and/or different rotation speed, while the first type allows to connect two domains presenting the same periodicity and rotation speed (more details in section 2-3.3.3 on page 2-38).
3-6
Batch Mode
This section provides all available information to launch installed NUMECA software from a shell without using HEXPRESS™ interface.
How to launch on UNIX.
1. Create a domain "user_prefix.dom" and topology "user_prefix.igg" files using HEXPRESS™ interface.
2. Start HEXPRESS™ to create a mesh from those files by typing:
hexpress -batch -project /mesh-full-path/mesh.igg -niversion 31_# -print
The command line to start the grid generator HEXPRESS™ contains its name, the full path name of the mesh (and of the domain located in the same directory and with the same user prefix) and the HEXPRESS™ release that will be used. The "-batch" option avoids the display of the HEX- PRESS™ graphical user interface.
This command should be used with HEXPRESS™ standalone version only. For FINE™/Open and FINE™/Marine packages, please change "31_#" to "open31_#" or "marine31_#" respectively.How to launch under Windows.
1. Create a domain "user_prefix.dom" and topology "user_prefix.igg" files using HEXPRESS™ interface.
2. Start HEXPRESS™ to create a mesh from those files by typing:
d:\NUMECA_SOFTWARE\Hexpress31_#\bin\hexpress.exe -batch -project /mesh-full-path/ mesh.igg -print (on Windows 32bits)
d:\NUMECA_SOFTWARE\Hexpress31_#\bin64\hexpressx86_64.exe -batch -project /mesh-full- path/mesh.igg -print (on Windows 64bits)
The command line to start the grid generator HEXPRESS™ contains its full path name, the full path name of the mesh (and of the domain located in the same directory and with the same user pre- fix) and the HEXPRESS™ release that will be used. The "-batch" option avoids the display of the HEXPRESS™ graphical user interface.
In order to use HEXPRESS™ included in FINE™/Marine or FINE™/Open package, "Hexpress31_#" should be replaced by "FineMarine31_#" or "FineOpen31_#".
Batch mode treats also multi-domains meshes and computations of full non matching connections.4-1
Overview
This chapter is presenting the different CAD operations necessary to convert respectively a CAD model into a computational domain to mesh within HEXPRESS. The resulting computational domain is stored in a file with extension ".dom" (see section A-4 on page A-2 for a description). Different CAD operations allow to create the solid model which will be converted into a computa- tional domain: unification of bodies, bounding box creation, bodies subtraction and bodies intersec- tion. After conversion to a discretized computational domain, further tools are available to edit the computational domain and to merge surfaces.
Figure4.1.0-1 presents a flow chart of the successive CAD manipulations needed to create a valid computational domain for HEXPRESSstarting from Parasolid™ or CATIA models, STL trian- gulations and StarCD surface meshes:
1. A bounding box can be added to Parasolid™ or CATIA bodies to define the computational domain of the required region surrounding bodies, e.g. for external flow simulation.
2. Parasolid™ and CATIA bodies can be added, subtracted or intersected.
3. The solid model of the computational domain is then exported, in a discretized format, by triangulating the surface of its closed volume.
4. The triangulation of the computational domain, annotated with geometry attributes, can be
exported into a ".stl" and a ".prop" file for further editing.
5. Triangulations can be directly imported using a ".stl" format file together with associated property file ".prop", which gives a geometry attribute to each triangle of the triangulation. This additional information allows the automatic creation of topological information by HEXPRESS.
6. An additional tool allows to import StarCD surface meshes and convert them into a trian-
7. Merging of topological surfaces can be performed on the triangulation model to simplify the meshing process. Merging of surfaces decreases the number of topological entities in the domain, especially the number of curves which must be captured by the mesh generator (see section 6-7 on page 6-33 for a discussion of the corner and curve mesh capturing func- tionalities).
FIGURE 4.1.0-1 HEXPRESS CAD handling