Lecture 6: CAD Import Release. Introduction to ANSYS Fluent Meshing

Transcription

1 Lecture 6: CAD Import 14.5 Release Introduction to ANSYS Fluent Meshing 1

2 Fluent Meshing 14.5 Assembly meshing Workflow This Lecture Tessellated or Conformal CAD import Cap Inlet/Outlets, Create Domains/BOI Create Size Function/ Material points Individual Wrap or Change to Wrap Import Real Creations Virtual Creations Extract Flowvolume (only) Multiple Fluids/Solids Extract Fluid + Solid Wrapping Operations Gap closing Wrap Flow Volume Make Mesh +Improve Gap closing Sew Improve Surface mesh Auto Mesh -Prism Setup -Tet or HexCore Volume mesh 2

3 Agenda CAD Import Formats CAD Import Standard Options CAD Import Advanced Options Appendix Suggested usage Advanced batch CAD conversion features 3

4 Agenda CAD Import Formats CAD Import Standard Options CAD Import Advanced Options Appendix Suggested usage Advanced batch CAD conversion features 4

5 CAD Import Fluent R14.5 utilises Workbench CAD import tools to read CAD files directly. Workbench must be installed to have the ability to access the CAD import option. Many require license keys. Converted to Faceted geometry on import On-the-fly triangulation (Fluent Meshing has no geom kernel) Conformal or non conformal options Available Formats are ANSYS WB formats; agdb, meshdat, mechdat ANSYS legacy formats: tin (ICEM CFD), dbs (Gambit) Standard/Free CAD formats; Iges, STEP, ACIS, Parasolid Spaceclaim files:.scdoc Licensed readers; Autodesk Inventor, CATIA V4, CATIA V5, Creo Parametric, JT Open, NX, SolidWorks Plug-ins: Autodesk Inventor, CATIA V5, Solid Edge, Creo Parametric, JT Open, NX, SolidWorks, NOTE; most of these are Windows and must be configured using ANSYS CAD Configuration Manager Non-CAD formats; STL (note for STL the faceting input parameters are irrelevant and will have no effect) Native PMDB (Part Manager Data Base) format 5

6 Agenda CAD Import Formats CAD Import Standard Options CAD Import Advanced Options Appendix Suggested usage Advanced batch CAD conversion features 6

7 CAD Import Standard Options (1) CAD Import options Single File import Browse and select a file For assemblies choose the assembly master file (e.g. *.CATProduct for CATIA V5) Multi-file import De-select Import Single File Select a Directory + a pattern (*.agdb, *.*). Useful for assemblies in separate files Standard Options Import Curvature Data from CAD Recommended for improved size function calculation Curvature calculations for size function will be based on CAD surfaces and not faceted geometry Append Will add any CAD files to the currently loaded geometry rather than overwrite Useful if user wishes to import different CAD files with different import (tessellation, etc) options Single File Import Multi File Import 7

8 CAD Import Standard Options (2) Feature Angle Feature Edge Zones are created on import of CAD Feature Angle specifies the angle change required for a CAD curve to be classed as a feature i.e. it is an input to control Feature Edge Zones generated at import Note that The default of 40 is generally good and If required, features can be created inside Fluent Meshing from the faceted representation Scale Factor Scales the geometry on import if required Zone Name Prefix Apply a prefix string to all Face and Edge Zones for current import Useful for multiple imports Imported Face Zones Imported Edge Zones 8

9 CAD Import Granularity in Object Example Mixer-T with 4 bodies in 2 parts Note that Face Zones can also be separated inside Fluent Meshing after CAD import 9

10 One Zone Per File One Zone Per File is useful when each object or set of surfaces is contained in a file with a meaningful name E.g. STL files named by part/body Import all *.stl files within folder One zone per file will name objects and face zones after the file name 10

11 Agenda CAD Import Formats CAD Import Standard Options CAD Import Advanced Options Appendix Suggested usage Advanced batch CAD conversion features 11

12 CAD Advanced options Read CAD in Subdirectories Only available during Multi-file import Useful if users have a set of tree-like directories containing assembly/sub-assembly files Save PMDB CAD Advanced Options PMDB is an intermediate file format which contains the interpreted geometry data prior to tessellation After initial import the user can more quickly change tessellation options by reading this PMDB file instead of the original CAD to avoid slow re-read and interpretation of the original geometry data Generally recommended but strongly recommended for large cases - Miscellaneous options Make Objects Independent ensures that objects are made independent (objects do not share face zones) on import. This is applicable to cases where face zones are shared between objects Import Part and /or Body Names is recommended and is on by default 12 Continue on Error continues the import of the CAD file(s), despite errors or problems creating the faceting on certain surfaces, or other issues Enclosure Symmetry Processing allows processing of enclosure and symmetry Named Selections during import. This option is disabled by default and is only applicable to ANSYS DesignModeler (*.agdb) files Length Unit should be set to units user wishes to work with inside Fluent Meshing (which is unitless)

13 Tessellation 1 Tessellation Refinement Tessellation Refinement Fast, STL-like tessellation of the geometry with no regard for quality or connectivity of triangles Inputs are based upon length unit chosen (m, mm, etc) Tolerance specifies the tolerance for the tessellation (faceting) refinement when Tessellation Refinement is selected. The default value is 0, which implies no tessellation (faceting) refinement during import. Max Size specifies a maximum facet size for the imported model to avoid very large facets. Zero default means unlimited max size. 13 Note on Tessellation Tolerance: It is recommended that you use the default value of 0 for an initial (diagnostic) import. You can then determine the minimum size you intend to use for the mesh and import the file(s) again using a Tolerance value 1/10th the intended minimum mesh size. Tessellation Refinement is Recommended for very large Assemblies where shrinkwrap is planned to be used i.e. connectivity is not as important

14 Default Vs Refined Tessellation Refinement Default no refinement Tolerance = 0.1 mm Facets in the original import should be smaller than final mesh requirement to ensure smooth curvature capture! 14

15 Poor Geometric Tessellation Here we see an example of poorly (too coarsely) tessellated geometry. The wrapped mesh reflects this coarse faceting even though the mesh size is as required. Always check curvature is captured well enough in the initial geometry before proceeding to meshing! Fluent Meshing relies on imported surface facets being close to the CAD representation! Initial Geometry Wrapped Result 15 Poor faceting on curved surfaces

16 Tessellation 2 Conformal Tessellation Tessellation Refinement High Quality, CFD-like faceting taking care to give good quality where possible and fully connected facets Inputs are based upon length unit chosen (m, mm, etc) Min Size specifies the min facet size which will be reached in areas of high curvature/proximity Max Size specifies a maximum facet size Edge Proximity enables the use of the edge proximity size function for creating the conformal tessellation, based on the number of cells per gap specified Cells Per Gap specifies the number of layers of elements to be generated in the gap for the edge proximity size function Merge Nodes allows you to merge free nodes after import. Nodes will be merged automatically at the object level with a tolerance of 1e Conformal Tessellation takes more time but is recommended for simple to medium geometry or where cut-wrap/cutcell are planned to be used (connectivity more important)

17 Conformal Faceting - Edge Proximity Edge Proximity during conformal faceting is only relevant if the user wishes to try to create the volume mesh from the original imported geometric faceting or to use Meshed size function to set mesh sizings later. If a wrap or cutcell method is to be used in Fluent Meshing then proximity refinement can be applied using Advanced Size Functions at a later stage. 17

18 CAD Advanced Option - Named Selections By default Import Named Selections is on inside the Advanced Options panel If required, user can apply boundary naming convention in their CAD tools and bring them through E.g. Named Selections in Design Modeler and then export.agdb E.g. Publications from CATIA V5 Named Selections can sometimes be unrequired for analysis e.g. Layer or Color labeling from CATIA will come through as a NS. These can be removed by adding Ignore options by Pattern/Expression 18

19 Surface or Solid bodies Surface Bodies will come through into Fluent Meshing with the sheet post fix in the Object Name Users should be aware of these Surface Bodies which may need removing if duplicate (as in this example case) but also could need capping to create a closed object before proceeding to wrap/cutcell etc View free faces to create caps by edge select and F5 create 19

20 Agenda CAD Import Formats CAD Import Standard Options CAD Import Advanced Options Appendix Suggested usage Advanced batch CAD conversion features 20

21 Appendix 14.5 Release 21

22 CAD Import Model Size Large/Complex Model size Large ~ 100s 1000s of bodies/parts of low-medium complexity OR small cases of very high complexity (100s-1000s of small surfaces making up few bodies/parts) Import first with default advanced options (quick-read) except switch save pmdb to YES. (Import coarse, light grid with no faceting refinement to examine conversion and understand best import settings) Re-import the.pmdb file with faceted refinement tolerance setting to relevant value based on min feature size ~1/30 th min feature size (0.1*min-cell-size with 3 cells across gap) If all bodies are solid then the conformal faceting option can be tried also, which will take longer but remove the wrapping step later Examine curved areas -> Is faceting sufficient? If no then re-import with lower tolerance/min-size and re-examine For Extremely large models, special methods are available to group objects on import E.g. lump nuts and bolts into single object rather than individual objects Requires use of a batch script outside Fluent Meshing which has additional options (see appendix) 22

23 CAD Import Model Size Medium Model size Medium ~10s to 100s of bodies/parts of low-medium complexity Repeat quick-read as above with no refinement (default) to save pmdb If dirty geometry exists (gaps, holes, not closed volumes) Re-import as above with faceted refinement tol~1/30 th min feature size and ensure curved regions and features are captured well before proceeding If geometry is relatively clean (each body, part is a closed volume) Re-import with conformal faceting, setting max size 3-5x smaller than the final min and max required in surface mesh and lower curvature angle than final mesh requirement. Examine geometry in critical areas to ensure sufficient curvature capture etc Single closed part Import directly with conformal faceting with sizing relevant to final mesh sizing Faceting at import can be used directly for volume meshing in some instances (edge proximity should be switched on to resolve small gaps/faces better) Additional options are available in command line batch reader to optimise conformal faceting and apply e.g. face proximity as well as edge proximity to ensure e.g. N cells across gaps. See appendix for more info on Batch CADReader. 23

24 CAD Import Low Complexity/ Small Model size Low part count with ~<100s of surfaces per part Import directly with conformal faceting following above conformal faceting requirements Single closed part Import directly with conformal faceting with sizing relevant to final mesh sizing Faceting at import can be used directly for volume meshing in some instances (edge proximity should be switched on to resolve small gaps/faces better) Additional options are available in command line batch reader to optimise conformal faceting and apply e.g. face proximity as well as edge proximity to ensure e.g. N cells across gaps. See appendix for more info on Batch CADReader. 24

25 Advanced CAD Options A number of additional CAD read options are available for Fluent Meshing but only through a batch reader (beta) which works outside the Fluent Meshing graphical interface Occasionally, users may benefit from extra options for tessellation including Ability to lump similar parts into one zone (reduction of zones in Fluent Meshing for large assemblies) Ability to use ICEMCFD tessellation Ability to enforce face-face proximity size function for conformal faceting 25

26 CAD Reader XML Each time the CAD reader is used an XML is created in background which can be found in the temp directory which can be accessed by typing %TEMP% into the quick launch on Windows By ordering the contents of this folder by date you should see the most recent options#.xml file which will contain the data for the last CAD read. This file can be edited to add other tags to run in the batch CAD reader. Copy this file into your working directory. 26

27 Editing XML File XML Example Some of the xml lines are not compatible with running in batch and must be edited/removed We remove the Merge to get multiple files and we remove OutputPath and replace with OutputDirectory which is identical to InputDirectory Note that capitals are important and xml flags on RHS have / in them! 27

28 Edited XML File Now to process this XML in batch we need to use a.bat file and point to this XML file see next slide 28

29 CAD Batch Reader beta feature runcadreaders.bat is found in C:\Program Files\ANSYS Inc\v145\commonfiles\CPython\winx64\Ansys\TGrid Shift RMB in whitespace in the folder gives option to open command prompt here Execution of this bat file result is.tgf (tgrid faceted format) files which can be manually read into TGrid Executing runcadreaders.bat -h gives all flags 29

30 Running Batch Reader with Edited XML The key flag required to run from XML file is runcadreaders.bat a /mydirectory/options.xml Example useful XML lines: Switch on face-face proximity refinement (very CPU expensive) <ConformalFacetingProximitySourceType>FaceFace</ConformalFacetingProximitySourceType> Switch on ICEMCFD Faceting (check Face and Edge zones and use with care) <UseICPartMgr>Yes</UseICPartMgr> Set a different min size for proximity SF calc compared to curvature min size <ConformalFacetingProximityMinSize>0.11mm</ConformalFacetingProximityMinSize> Proximity can be too sensitive to very small gaps at times and user may need to adjust tolerance <ConformalFacetingGapToleranceFactor>0.1</ConformalFacetingGapToleranceFactor> More options exist so please contact support if something is required 30