Turbocharger Geometry Clean Up and Meshing using ANSA

In this challenge we are using ANSA pre processsor tool to clean up the CAD file of a turbocharger. After CAD clean up we will surface mesh the complete geometry, then we will also generate volume mesh. below are the steps and visual representation to achive the task.

• Geometry clean up

1. First, open the file in ANSA. After opening the file, we can see that there are many single cons and missing surfaces.
2. There is a hidden pink surface overlapping with green compressor casing. We can make it visible and then delete it bu using universal delete button.
3. We can see that the surface is missing at the compressor casing inlet. We can fix this by clicking new button in the Faces menu. Then select COONS from the pop-up window.
4. Then select the edges one by one in ENT mode, where you want to create the new face. Then finalize the selection by clicking the middle mouse button and click ok.
5. Now rectify the missing impeller casing surface. To rectify this click the project button in Hot points menu. Then click at a point on the rounded edge of impeller casing, an arrow will appear and a pop-up window will appear. Now enter 0.5 in the window this will split the edge into two equal parts and new hot points will be created.
6. Create five hot points on each side and then use these hot points to create the new surface one by one to complete the missing surface of the impeller casing.
7. There is an error at the compressor casing outlet. A protruding surface is left out. We have to delete that surface. To delete, click project button in hot points menu, then select the edge under the protruding surface and click middle mouse button. Then select the above surface and click middle mouse button. This will split the surface into two seperate surfaces
8. Now use topo button in the faces menu to create a triple con. After that we can delete the protruding surface. 

1. As we can see in the above image, there rotor shaft, compressor casing and impeller casing are overlaping. We have to delete the overlapping surfaces.
2. First hide the rotor shaft and then delete the extra surface from the compressor casing and impeller casing. This will lead to formation of single cons at each side.
3. To remove this single con, click project button from cons menu. Then select the cons and finilize the selection by middle mouse button. Then select the face of rotor shaft and click middle mouse button. this will remove the single con created. 
4. repeate the above procedure to rectify the issue near the impeller casing.

• Setting PID

1. All the PID are already assigned but the names are all same. We have to edit the PID according to the different names of the geometry.
2. To do this, click on the P button on the top. Properties window will open, now edit the PIDs.
3. Use compress button to compress all the unused PIDs.

• Combining the volumes

1. In the above image all the PIDs are different but we need to combine all PIDs into a single volume.
2. To do this, click topo button in the faces menu. And the left click drag the mouse at the edge which you want join then click middle mouse button.
3. This will join the two different volumes into one. Now we have to delete the extra overlapping surface from the two joined volumes.
4. Use the above steps to join all the different volumes into one single volumes.

• Surface Mesh

PID Name            Element size

Blades stage 1      - 1 mm
Blades stage 2      - 1 mm
Shaft rotor         - 1 mm
Turbo casing        - 5 mm
Inlet casing cover  - 5 mm
Impeller            - 2 mm
Compressor casing   - 5 mm

Element type - TRIA

In this challenge we have to create different element size for different PIDs. Above is the data for element size for different PIDs and type of element.

1. Go to mesh module by clicking mesh button at the upper right corner of the screen.
2. Make visible only those PIDs which have same element size.
3. First we will make visible only those PIDs which is needed to be meshed with element size 1 mm.
4. Then click length button in the parameters menu, to set the desired length of the element.
5. Now hold and drag the mouse around the complete geometry to select all the edges.
6. After that click middle mouse button, a window will appear to set the length. Then click ok to discretize the complete geometry.
7. Now click free button in the mesh generation menu.  After selecting free mesh, go to lower right corner of the screen and change the element type to tria.
8. Then drag the mouse around the complete geometry to select the whole geometry.
9. Then click middle mouse button to generate the mesh.
10. Repeat the above steps to mesh other parts of the goemetry.
11. Note: When we will mesh the rotor shaft we have to enable the Remesh macros after clicking the length button in parameters menu. Remesh macros option will appear at the lower right corner of the screen after clicking the length button.

• Volume mesh

1. Before creating the volume mesh we have to completely close the all the openings, all the inlets and outlets. Then only we can create volume mesh.
2. We can close all the open faces by creating new faces. Click new button in the faces menu and then create new face where it is needed to close the open volume.
3. After closing the complete geometry, set the PIDs for these new faces.
4. After that, go to Volume mesh module and click define button in the volumes menu.
5. A window will appear containing the list of all the generated volumes. Right click on all the volumes and check if the voulmes is necessary or not. Delete the unnecessary volumes, unnecessary volumes are the one in which there will be no fluid flow.
6. Now click on Tetra CFD button in the unstructured mesh menu.
7. Then hold and drag the mouse over the complete geometry and click middle mouse button. This will generate the volume mesh. This process will some time, so leave the software as it is and wait for the process to complete.