Fluent User Services Center www fluentusers com Introductory

Fluent User Services Center www. fluentusers. com Introductory GAMBIT Training GAMBIT 2. 3 June 2006 CAD/CAE Data Import and Geometry Cleanup 3 -1 © 2006 Fluent Inc.

Fluent User Services Center www. fluentusers. com Introductory GAMBIT Training GAMBIT 2. 3 June 2006 Introduction u u Several translation methods available to enable data exchange with CAD/CAE systems. Translation can: l l u Geometry cleanup refers to processes required to prepare geometry for meshing. l l l u return incomplete, corrupt, or disconnected geometry return geometry details unnecessary for CFD analysis Fix incomplete or corrupt geometry and connect disconnected geometry Remove unnecessary details (defeaturing) Decompose geometry into meshable sections GAMBIT's virtual geometry operations and Semi-Automated Cleanup tools can help with the cleanup process. 3 -2 © 2006 Fluent Inc.

Fluent User Services Center www. fluentusers. com Introductory GAMBIT Training GAMBIT 2. 3 June 2006 CAD/CAE Data Exchange – Direct Translation u u u ACIS-based CAD/CAE programs (Auto. Cad, Cadkey, Turbo. Cad) can export ACIS files (. sat or. sab) which can be imported into GAMBIT. Parasolid-based CAD/CAE programs (Unigraphics, Solid. Works, PATRAN, ANSYS) can export Parasolid files (. x_t and. xmt_txt) which can be imported into GAMBIT. CAD/CAE programs using proprietary geometry kernel n Direct (single-stage) Catia V 4 or V 5. model file to ACIS translator s ADD-on (specific license key needed) s Contact your FLUENT account manager for pricing information 3 -3 © 2006 Fluent Inc.

Fluent User Services Center www. fluentusers. com Introductory GAMBIT Training GAMBIT 2. 3 June 2006 CAD/CAE Data Exchange – Standard Options u Standard Translation Options l l Translation uses an intermediate, neutral or standard file format Applicable for all CAD/CAE systems that can output: n n l STEP files (recommended) IGES files STEP (Standard for Exchange of Product model data) n n n International standard defining format for geometry and model information. GAMBIT supports AP 203 and AP 214 Preferred over IGES import. s Pro/E supports STEP export at no additional cost. s Other systems support STEP as add-on. 3 -4 © 2006 Fluent Inc.

Fluent User Services Center www. fluentusers. com Introductory GAMBIT Training GAMBIT 2. 3 June 2006 CAD/CAE Data Exchange – Standard Options u IGES (Initial Graphics Exchange Specification) l IGES can provide incomplete or disconnected geometry due to export issues with the CAD package. n l l Review summary of data before import to determine if there any errors. GAMBIT provides two options for IGES import n n l Faces without volumes Spatial (Recommended) s All imported geometry comes in as real, supports solids Native (Fluent) s Original IGES translator, does not support solids s Trimmed surfaces come in as virtual geometry. Other options available during import for n n Scaling the IGES file at import Removing stand alone entities Tolerant modeling and healing Virtual cleanup of small edges and faces. 3 -5 © 2006 Fluent Inc.

Fluent User Services Center www. fluentusers. com Introductory GAMBIT Training GAMBIT 2. 3 June 2006 Import Mesh and Import CAD u Import Mesh and some Import CAD options result in faceted geometry. l l u Least preferred approach. Options to create features using a Feature Angle. STEP file and Direct import options available for Pro/Engineer. l Direct import accesses Pro/E kernel. n u Requires add-on license. File-direct options (native file readers) available for Parasolid and Pro/E files. l Requires add-on license. 3 -6 © 2006 Fluent Inc.

Fluent User Services Center www. fluentusers. com Introductory GAMBIT Training GAMBIT 2. 3 June 2006 File Direct Import u File-Direct import options for Pro/E and Parasolid files. l l GAMBIT directly imports native files, such as Pro/E part files, eliminating geometry translation losses. Option to bring in either solid model or the flow volume. n End faces of the flow volume should be created in original CAD package. 3 -7 © 2006 Fluent Inc.

Fluent User Services Center www. fluentusers. com Introductory GAMBIT Training GAMBIT 2. 3 June 2006 Tolerant Modeling u Every CAD system uses a minimum numerical precision (tolerance) for describing the geometry. l u The ACIS kernel in GAMBIT uses a highprecision tolerance of 10 -6 (6 decimal places). l l u Coordinates of vertices/points, length of edges, size of faces, volumes. This precision may not be matched by the CAD/CAE software where the geometry was created. Problems can arise upon import such as disconnected edges and faces. Tolerant modeling is a technique which uses a variable or floating tolerance to connect geometry. 3 -8 © 2006 Fluent Inc.

Fluent User Services Center www. fluentusers. com Introductory GAMBIT Training GAMBIT 2. 3 June 2006 Tolerant Modeling u Available by activating the Make Tolerant option during CAD model import. l u Application l l l u Also available after import inside the Heal Face (or Volume) Form. All Geometry files Relatively large gaps Real ACIS volumes generated during import. Boolean operations subsequently possible l l Adding/Subtracting additional geometry Volume Extraction Retaining only ½ or ¼ of model Volume decomposition for better meshing 3 -9 © 2006 Fluent Inc.

Fluent User Services Center www. fluentusers. com Introductory GAMBIT Training GAMBIT 2. 3 June 2006 Smooth/Heal Real Geometry u Geometry imported from other CAD systems can lack the required accuracy and precision to render valid or connected ACIS geometry. l l l u This results from numerical limitations in original CAD system, neutral file formats, or differences in tolerances between CAD systems and ACIS. Use the check command to verify integrity of geometry/topology. Check the connectivity of geometry using connectivitybased color coding. Smoothing and Healing of Real geometry can help. l l l Smoothing is used to remove discontinuities in geometry. Healing is used to detect and correct inaccuracies in model geometry due to different tolerances and translator limitations. Available in the Smooth/Heal forms or as an option during CAD Import. 3 -10 © 2006 Fluent Inc.

Fluent User Services Center www. fluentusers. com Introductory GAMBIT Training GAMBIT 2. 3 June 2006 Smoothing and Healing Options u Smooth Options: l l u Healing options: l l l u Replace Bad Geometry: Removes discontinuities or “kinks” in geometry. Reduce Complexity: Simplifies the spline representation of geometry by reducing the number of control points. Simplify Geometry: Converts spline geometry to analytic geometry, whenever possible. Stitch Faces: Stitch together faces being healed to form one or more volumes. Repair Geometry: Changes the definition of the edges and faces of geometry so that the model “fits together” well, especially at boundaries. A tolerance is specified for some operations l l The maximum distance between old and new geometry. The maximum size of the gap between faces for Stitch faces. Auto: Automatically calculates the tolerance based on the size of the geometry being smoothed/healed. Manual: User can set tolerance (10 -3 by default). 3 -11 © 2006 Fluent Inc.

Fluent User Services Center www. fluentusers. com Introductory GAMBIT Training GAMBIT 2. 3 June 2006 Smoothing and Healing Examples Face smoothing Healing Faces Stitch faces options 3 -12 Stitch faces, Repair geometry options © 2006 Fluent Inc.

Fluent User Services Center www. fluentusers. com Introductory GAMBIT Training GAMBIT 2. 3 June 2006 Geometry Cleanup Operations u Geometry cleanup is a follow on step, after using Tolerant modeling, Healing and Smoothing, to connect and de-feature geometry, and other problems. l u Virtual geometry operations are used to perform geometry cleanup on edges and faces. l u Bridging gaps between edges/faces, small edges and faces, removing sharp angles, duplicate geometry etc. Merge, Connect, Collapse, Create from Wireframe etc. . The cleanup operations can be conducted manually or using semiautomated tools. l l Manual: Select the geometry for cleanup manually and then use virtual operations. Semi-automated: Use specialized cleanup tools to automatically find problem geometry for cleanup and then use recommended real/virtual operations. 3 -13 © 2006 Fluent Inc.

Fluent User Services Center www. fluentusers. com Introductory GAMBIT Training GAMBIT 2. 3 June 2006 Virtual Geometry u u Virtual geometry is “overlay” geometry that is defined based on underlying “host” geometry, which may be real or virtual. Virtual geometry is named and colored differently than real geometry. l u u u v_vertex, v_edge, v_face and v_volume. Virtual Face after Merging Three Non-Coplanar Faces Meshing and boundary assignment operations are unaffected by virtual geometry. Virtual geometry operations are accessed using dedicated virtual operation panels or virtual option on a real geometry panel. On performing a virtual operation, any higher/lower geometry that is connected also becomes virtual and the host geometry is hidden from view. l The host can be retrieved by deleting the resultant virtual geometry and deselecting the Lower Geometry option. 3 -14 © 2006 Fluent Inc.

Fluent User Services Center www. fluentusers. com Introductory GAMBIT Training GAMBIT 2. 3 June 2006 Virtual Geometry Operations u The virtual operations available are: l l l Merge: Replaces two connected entities (edge/face/volume) with a single virtual entity. Split: Partitions an individual entity (edge/face/volume) into two or more connected virtual entities. Connect: Combines two individual unconnected entities (vertex/edge/face) into a single virtual entity. l Collapse: Splits a face and merges the resulting halves with two neighboring faces. l Simplify Faces: Removes dangling edges. l Convert: Converts virtual geometry to real by sampling points on a mesh. l l Boundary Defined Virtual Face Unite: Unites two non-coplanar faces using locations selected on their boundaries. Stitch Faces: Creates virtual volumes from a set of connected faces. 3 -15 © 2006 Fluent Inc.

Fluent User Services Center www. fluentusers. com Introductory GAMBIT Training GAMBIT 2. 3 June 2006 Edge Connect (Virtual) u Edge Connect l l Also available in Vertex and Face Virtual (Forced) n l Pick two or more edges you want to connect Virtual (Tolerance) n n Every picked edge within the tolerance will be connected 10 % of shortest edge is recommended (default) The shortest edge is shown by clicking the Highlight Shortest Edge button The shape of the connected edge is an interpolated ‘average’ of the picked edges. s Use Preserve first edge shape to force result to assume shape of first edge in pick list. s Preserve first vertex location is available for vertex connects. 3 -16 © 2006 Fluent Inc.

Fluent User Services Center www. fluentusers. com Introductory GAMBIT Training GAMBIT 2. 3 June 2006 Edge/Face Merge u Virtual Edge/Face merge options l Virtual (Forced) n Create one single edge/face from all edges/faces Face merge Two faces l Edge merge One virtual face Virtual (Tolerance) n n n Merge all edges shorter than Max. Edge Length Merge all entities of higher entity angle than Min. Angle No input will merge all vertices connected to two edges only Max. edge = Min. angle = 135 3 -17 © 2006 Fluent Inc.

Fluent User Services Center www. fluentusers. com Introductory GAMBIT Training GAMBIT 2. 3 June 2006 Virtual Split u Edges, Faces and Volumes can be split using other virtual entities. Options are: l l Face (Virtual) Edges (Virtual) Vertices (Virtual) Locations (Virtual) n n Vertex locations can be adjusted after the split Limitations (for both face and volume split) s Split through voids, protrusions and dangling faces will create incorrect geometry s Order of picking is important s First and last location on a face must be on its boundary 3 -18 Face split One face (real or virtual) Two virtual faces © 2006 Fluent Inc.

Fluent User Services Center www. fluentusers. com Introductory GAMBIT Training GAMBIT 2. 3 June 2006 Volume Split (Virtual and Faceted) u Volumes can be split with l l Volume (real) Face (real) or Faces (virtual) n All edges of the face must be connected to the volume connected face virtual volume split one volume l 2 virtual volumes Locations (virtual) Pick locations on edges, in sequence, to define splitting face: Perform virtual volume split: Adjust split by sliding the virtual vertices (In Vertex Operations menu): 1 2 4 3 3 -19 Note: This can also be done after © 2006 Fluent Inc. meshing.

Fluent User Services Center www. fluentusers. com Introductory GAMBIT Training GAMBIT 2. 3 June 2006 Virtual Connect u Virtual Connect is available for vertices, edges and faces as options in the respective Connect forms. l l Virtual (Forced) – Pick two or more entities you want to connect. Virtual (Tolerance) – Every picked entities within the specified tolerance will be connected. n u For edge connect, you can select preserve first edge shape to force result to assume shape of first edge in pick list. l u 10% of shortest edge is default. Preserve first vertex is available for vertex connect. T-Junctions option is available for edges/faces at an angle or having gaps/overlaps. 3 -20 © 2006 Fluent Inc.

Fluent User Services Center www. fluentusers. com Introductory GAMBIT Training GAMBIT 2. 3 June 2006 Virtual Edge/Face Connect with T-Junctions u For edges, the T-junctions option splits edges by vertices that exist within a specified tolerance of the edges and then connects the split entities. l u Preserve first edge shape option avoids distortion of edge shape. For faces, T-junctions helps overcome common geometry problems in imported models such as gaps, mismatches and overlaps. l Utilizes projections, splits, and connects to overcome problems. T-Junctions with Preserve first edge shape on Edge Splits unconnected real edges/faces Overlapping Faces connected by T-Junctions connected virtual edges/faces 3 -21 © 2006 Fluent Inc.

Fluent User Services Center www. fluentusers. com Introductory GAMBIT Training GAMBIT 2. 3 June 2006 Boundary Defined Virtual Face Unite u Virtual option for Unite Faces can handle gross overlaps and gaps between faces. l l u Important locations for the final shape must be picked by user. Tolerance option Limitations l l l Order of picking boundary points is important. Gaps larger than the mesh size can create trouble during meshing Cannot handle large distances between overlapping faces Example: Unite square face in z = 0 plane with circular face in z = 0. 05 plane. Select 6 points F (A through F) IMPORTANT: C and E must lie on circular arc to obtain correct A shape E D 3 -22 C B © 2006 Fluent Inc.

Fluent User Services Center www. fluentusers. com Introductory GAMBIT Training GAMBIT 2. 3 June 2006 Virtual Geometry Operations u Convert - converts non-real entities to real l l l u Applicable to vertices, edges, faces, and volumes. Face conversions require that a surface mesh be present. Edges are sampled and real spline (NURBS) curve generated. Sampling controlled by the GAMBIT default Geometry. Edge. VIRTUAL_NUM_SAMPLING_POINTS Volume conversions require that all lower topologies can be converted Topology and any existing mesh are preserved. Face Simplify l l l Removes dangling edges and hard points from a face. Result is virtual face The face with dangling edge can also be split. 3 -23 Dangling edges © 2006 Fluent Inc.

Fluent User Services Center www. fluentusers. com Introductory GAMBIT Training GAMBIT 2. 3 June 2006 Comparison of Face Unite, Merge, and Connect u Unite (real) l u Unite (virtual) l l u Real Unite Gaps or overlaps are allowed. There is no edge unite command. Merge l l l u Faces must have matching tangents. Operates on real or virtual geometry. Result is always virtual. Faces must share an edge but they need not be tangent Merge Connect l l l Operates on real or virtual geometry. Result can be either real or virtual. Replaces selected entities with a single entity. 3 -24 Tolerance Connect © 2006 Fluent Inc.

Fluent User Services Center www. fluentusers. com Introductory GAMBIT Training GAMBIT 2. 3 June 2006 Semi-Automated Cleanup Tools u u Clean up on models containing a large number of faces can be tedious. Cleanup Tools can semi-automate this process using virtual and real operations: l l u Finding the problem areas Suggesting fixes More information in the Semi-Automated Cleanup lecture. 3 -25 © 2006 Fluent Inc.

Fluent User Services Center www. fluentusers. com Introductory GAMBIT Training GAMBIT 2. 3 June 2006 Working with CAD Geometry: Procedure 1. Import CAD geometry. l First preference should be for native formats, then the standard formats. n l Preparing the model in CAD can smooth the cleanup process. n l STEP is usually better than IGES. See Appendix for guidelines on CAD Interoperability for different packages. Turn on Tolerant Modeling. 2. Delete all unnecessary geometry. 3. Check validity of imported geometry. 4. Correct invalid geometry (Smooth/Heal and/or reconstruct). 5. Check connectivity by color coding l l Helps distinguish between connected and unconnected entities. White and Orange colors indicates disconnected entities. 3 -26 © 2006 Fluent Inc.

Fluent User Services Center www. fluentusers. com Introductory GAMBIT Training GAMBIT 2. 3 June 2006 Working with CAD Geometry: Procedure 6. Connect Geometry (Manual or Semi-Automated Cleanup) l l l Real/Virtual connect of vertices, edges, and faces, in steps, based on increasing connect tolerance Connect with T-Junction Option. Use forced connect operation for entities out of tolerance 7. Defeature/Simplify Geometry (Manual and/or Semi-Automated Cleanup) l l Merge small edges and faces with neighbors. Merge faces at large angles. Remove hard edges. Remove sharp angles for better meshing. 8. Create additional geometry (if necessary) and form volume(s). l l l Some of this may need to be done before resorting to virtual geometry commands so that real Boolean operations are available. Bridge real and existing virtual geometry together using virtual geometry. In 3 D, use face stitch command to create virtual volumes. 9. Decompose volume (if necessary) using virtual split operations. 10. Generate the mesh 3 -27 © 2006 Fluent Inc.

Fluent User Services Center www. fluentusers. com Introductory GAMBIT Training GAMBIT 2. 3 June 2006 Appendix 3 -28 © 2006 Fluent Inc.

Fluent User Services Center www. fluentusers. com Introductory GAMBIT Training GAMBIT 2. 3 June 2006 General Guidelines for CATIA u u u u Wherever possible use basic geometry and primitive solids for model creation. Big extracted surface can be broken into smaller surfaces by using the Dissemble option. If one or more bodies (volumes) in CATIA are sharing the same face then there will be duplicate faces upon import in GAMBIT. Hide the sketches, extracted edges and boundaries before exporting file from CATIA; otherwise, these entities will appear as edges in GAMBIT. For assemblies, confirm that all component files are in the same directory. Use tools available in CATIA to validate geometry prior to export. If using STEP, import the data back for a loop test to certain that the solid model data in STEP file can be recreated in CATIA. 3 -29 © 2006 Fluent Inc.

Fluent User Services Center www. fluentusers. com Introductory GAMBIT Training GAMBIT 2. 3 June 2006 General Guidelines for Pro/Engineer u For a better data exchange, it is recommended to create models in Pro/E with absolute accuracy from the beginning. l u u u The setting enable_absolute_accuracy yes needs to be included in configuration file config. pro. Delete all non-referenced geometry and external reference. Do not use any suppressed construction geometry (activate all layers). For assemblies, confirm that all component files are in the same directory. Components of an assembly should have names no longer than 16 characters. Before export, use Info→Geom/Check to check for design problems. Indicated features are likely to cause problems in the target system. If using neutral formats, import the data back for a loop test to certain that the solid model can be recreated in Pro/E. 3 -30 © 2006 Fluent Inc.

Fluent User Services Center www. fluentusers. com Introductory GAMBIT Training GAMBIT 2. 3 June 2006 General Guidelines for Unigraphics u u u u Avoid modeling practices that creates unparameterized features. It will reduce corrupt solids and will facilitate repair of invalid geometry. Wherever possible avoid using blend features in Unigraphics. Use of tolerant modeling feature in Unigraphics should be avoided. Use File→Utilities→Part Cleanup option to delete any empty groups and un-referenced objects from the part file. Use Info→Analysis→Examine Geometry command to analyze the model and fix any errors prior to export. For assemblies, confirm that all component files are in the same directory. If using intermediate file, import the data back for a loop test to be certain that the solid model data in the file can be recreated in Unigraphics. 3 -31 © 2006 Fluent Inc.

Fluent User Services Center www. fluentusers. com Introductory GAMBIT Training GAMBIT 2. 3 June 2006 General Guidelines for Solid. Works/Solid. Edge u u u u Use a tighter tolerance (close to 10 -6) in Solid. Works/Solid. Edge. Wherever possible use basic geometry and primitive solids for model creation. Make all geometry visible and selectable. Remove unnecessary geometry, layers, annotation from the file(s). Delete all non-referenced geometry and external reference. Do not use any suppressed construction geometry (activate all layers). Solid models should be prefered over the wireframe. For assemblies, confirm that all component files are in the same directory. Use tools available in Solid. Works/Solid. Edge to validate geometry prior to export. If using intermediate formats, import the data back for a loop test to be certain that the solid model can be recreated in Solid. Works/Solid. Edge. 3 -32 © 2006 Fluent Inc.