Geometry clean-up

MESHING THE TURBOCHARGER IN ANSA:-

OBJECTIVE:-

• Creating an error free Geometrical Turbocharger for meshing.
• Performing an error free surface for 2D surface meshing and Then Performing volume meshing on the Turbocharger.

WHAT IS ANSA? :-

ANSA is a Computer-aided engineering tool for Finite Element Analysis and CFD Analysis widely used in the automotive industry. It is developed by BETA CAE Systems. The software is distributed world wide by a number of BETA CAE Systems subsidiaries and business agents. In the United States, it is distributed by Beta CAE Systems, USA, based in Farmington Hills, Michigan.

ANSA maintains the association between CAD geometry and the FE mesh. This means that the FE meshes are better representations of their geometric parents. Also it is easy to maintain and update any changes in the geometry by simply reworking the updated area instead of recreating the FE from scratch.

It carries several proprietary algorithms for meshing suitable for both CFD and structural models. ANSA was initially standing for \'Automatic net generation for structural analysis\', but the software has gone beyond that very quickly. ANSA has broadly six menus which are used to do various activities those are: TOPO MESH, VMESH ,DECK-SOLVER, MORPH ,HBLOCK.

(source:wiki)

Different Type of Modules in ANSA:-

• TOPO - Set of tools for Geometry clean-up and for setting up of PIDs.
• MESH - Tools to generate Surface Mesh or 2D Mesh.
• VOLUME MESH - To generate solid or 3D Mesh.
• DECKS - Tools based on different solvers such as ABAQUS, RADIOSS, ANSYS etc.
• MORPH - Advanced tool to capture geometry more accurately while meshing.

CROSS - Tools to define Cross Section.

METHODOLOGY:-

1. Importing the CAD model.
2. Display set-up.
3. Geometrical clean-up
4. Assigning PID\'s
5. Merging volumes
6. Meshing with specific PID lengths
7. Rectifying Mesh Errors
8. Preparing the model for Volume Mesh
9. Volume Meshing

1). IMPORTING OF CAD MODEL

On Importing the CAD model ,We are able to see the WireFrame model in the Drawing Area.

Go to file > Open > Browse the location of the CAD model > Select it click on Enter.

2). Display set-up

The model which we have imported opens in wireframe mode. Inorder to use it we need to set it right for use.

Bottom Tool Bar > Shadow Mode > Drawing Mode > PID

The Edges cannot be visible in this mode. Inorder to display that

Toolbar > Quality Criteria > Presentation Parameter > Select Draw CONS IN PID,MID,...like in ENT mode > Apply > OK.

3). Geometrical clean-up:-

• The main intention of Geometry clean-up is to eliminate single CONS and Reduce triple CONS as many as possible.
• In this model there are lot of patches and Geometry intersections to clear.

• Geometry check-up is done to check whether there are any errors in the model like Unclosed faces, Super Imposing faces, etc..

  Toolbar > checks > Geometry > Visible > Execute > Check for the green tick beside geometry > close the window.

• The geometry is checked using the checks button and selecting the geometry checks option as shown

• The geometry check dialog box displays various errors in the geometry.
• The above seen errors are cleaned up using various options like coons, fill hole and cut commands.
• After performing cleanup the geometry is again checked for any errors using geometry checks.

4). Assigning PID\'s:-

• PID\'s are assigned by set PID command and selecting respective parts, Below are the set of PID\'s.

5). Merging volumes:-

• The main idea of merging volumes is to create an error free volume mesh
• To ensure the error free volume mesh we must merge volumes and delete the common surfaces.
• In turbocharger:- blade stage1, blade stage2, shaft rotor,& impeller are merging as one volume to ensure continous one volume.

• Merging of surfaces can be done by combining the volumes and deleting the common surfaces.
• white-boxes:- represent operation of topo between blades.
• Blue-box:- represent operation of project and topo( between blade stage1 & rotor shaft).
• Black-box:- represent project and mesh( between blade stage2 and rotor shaft)
• Red-box:- represent topo and cut operation on impeller and again topo to join.( between impeller and rotor shaft).
• After combining the volumes the common surfaces and volumes must be deleted.

6). Meshing with specific PID\'s:-

• Switch to mesh mode and perform the mesh operation according to the below length specifications.

Surface Mesh

7). Rectifying the Mesh Errors:-

• After performing mesh we find some unmeshed faces, glitched surfaces(Because of some overlaps and specific PID lengths)
• To overcome overlaps, delete the overlapped surface and do project to get rid of SINGLE CONS.( one between turbo casing and shaft, another between compressor casing and rotor shaft).
• There is still mesh quality correction where compressor casing and rotor shaft meets, make a segment using cut command shown as below.

8). Preparing the model for volume mesh:-

• Four more PID\'s are created to close the entire work volume so that it is easy to work.
• Compressor casing inlet
• Compressor casing outlet
• Turbo inlet
• Turbo outlet
• Then mesh the unmeshed surfaces using free mesh.
• Make sure that every part must be surface meshed before going to volume mesh.

9). Volume mesh:-

• Switch to v-mesh mode > select define under > volumes and > delete unwanted volumes

• Then select > tetra mesh under > unstructured mesh and select the whole model for mesh.

RESULTS:-

• The results of Geometry checks, surface mesh checks, & volume mesh checks are shown below:

• As shown in the results that everything is fine with geometry and meshing as well.

CONCLUSION:-

• All the Topological errors in the geometry have been cleaned.
• Surface mesh & Volumetric mesh have been created sucessfully.