Week 3 Challenge : CFD meshing on Turbocharger
CFD MESHING ON TURBOCHARGER:-
Turbocharger -A turbocharger is a device fitted to a vehicle’s engine that is designed to improve the overall efficiency and increase performance.
A turbo is made up of two halves joined together by a shaft. On one side, hot exhaust gasses spin the turbine that is connected to another turbine which sucks air in and compresses it into the engine. This compression is what gives the engine the extra power and efficiency because as more air can go in the combustion chamber, more fuel can be added for more power.
Objective-
- 2D and 3D meshing on turbocharger
- Exploring 2D nad 3D ansa tools.
- Geomerty clean up like removing single cons, adding surfaces and removing useless surfaces.
- step by step explaination of compete process.
Original Geometry-
After uploading geometry into ANSA , set geomerty to PID mode. This is our original geometry , as we can observe there are mixed green and pink colors on surface, these are overlapped surface. our geometry is filled with overlapped , intersecting and extended surfaces, all these surface requires to be removed by deleting them. There are multiple single cons present in geometry and some unnescessary double cons.
After putting geometry into wire frame mode we can see our single , double and triple cons clearly. All single cons are due to extended , intersecting or absent surfaces. All of them requires to be fixed.
Starting geometry cleanup
Intersected surface
Top of turbocharger has some intersectiing surface which we can see in secong image(higlighted in purple). Use intercting tool from topo mode and select first intersecting surface anf then secongd intersecting surface and do middle click. This will seperate intersected surface from geometry.
Extended surface is seperated from geometry and we will delete both them using delete option. We can se dash lines on extended surface which was absent before using intersecting tool. now select surface by clicking on dashed lines and delete them.
Overlapped Surface
In our original we have seen mixed colors on surface due because there was overlapped surface. This time we have have removed original surface using not tool in ANSA so that we can clearly see pink color surface which was extra and needs to deleted. Choose pink surface and delete them. When we examined the complete geometry we observed that there are small overlapped surface present inside geometry like on shaft and rotor which we will delete by following above discussed procedure.
SINGLE and TRIPLE CONS
RED color line represent single and blue color double cons. single cons appears mostly due missing surface or seperated cons.
we will follow two steps to remove single cons
- Create missing surfaces by using tools from face tools option
- Join two single cons seperated by small distance using paste option. If there is con on one surface and no cons on other surface , in such case use project option to project con of one surface on other surface and then join them together using paste option.
In below geometry we cannot directly use face tool to create new surface as surface created was not acceptable, so we will try splitting the surface by creating hotpoints. Start created hotpoint at showed locations and then create small new surface using thise hotpoints first.
Now as we can see missing surface is square in shape after we created previous surface using hotpoints. It is easy now to create new surface by using face tool as missing surface is simple square and not some complex geometry. Select cons and do middle click
In case of turbo casing also we will create hot points and then try to join them using face tool 
Hot points created
Using face tool to create new surface 
New surface created
Changing PID names:-
Give respective proper names to repective PID's
Geometry after TOPO cleanup and closing the geometry:-
IN geometry shaft should be completely hollow with no hindrance , we will remove all surface to make shaft hollow so that it would be considered as one surface 
Creating 2D mesh:-
We will follow below guidelines to create mesh length of different size for different PID's
- Blade stage-1 = 1 mm
- Blade stage-2 = 1 mm
- Impeller = 2 mm
- Shaft rotor = 1 mm
- Turbo casing = 5 mm
- Compressor casing = 5 mm
- Inlet casing cover = 5 mm
Steps to create 2D mesh
- Give quality criterias of minimum and maximum mesh length for particular mesh size. Suppose if mesh length is 5mm then we can take minimum mesh length as 3 and max as 7.
- Give mesh properties , choose tria elements and specify mesh length and give min and max value for mesh length.
- Choose length tool a pop up box will appear which will ask to give perimeter and macros length .
- Choose perimeter and select PID by right click and dragging mouse to cover whole PID or you can use entity mode. Do middle click.
- Choose macros and select PID by using PIDregion tool and then do middle click.
- Select spot mesh and select PID by using pidregion.
2D mesh outer casing
2D mesh Impeller
2D mesh Turbo casing
2D mesh Blades
NOTE: While meshing you will come across a problem which is disappearence of meshes from regions where 2 PID's with different mesh length are joining. This happens because of mesh size domination as ANSA is confused which mesh size to follow at transition points between two PID's.
To cope with this problem
- while giving macros length you will see mesh length varying in a range in which minimum length will be of one PID and maximum length will be of PID on which youn are meshing. So dont give any input in macros and select spot mesh option to mesh.
- In below picture we can observe mesh size of green color PID is changing as it approached pink color PID. This is adjusting mesh size at joining point of PID's with different mesh length.
VOLUMETRIC MESHING
Volumetric mesh can be done only after 2D meshing . To check how many surface are available for volumetric meshing choose define option from volumes and then wholebd and click ok.
This step will show PID's available for volumetric meshing. In our case we got 8 PID's.
To check which PID's to keep and which to delete
- PID's which represents thickness of geometry are required to be deleted.
- PID's which represents volumes inside of geometry are required to be kept and these will be meshed
PID to be deleted
PID to be deleted
PID to be deleted
PID to be deleted
Volumes to keep
PID to keep
PID to keep
PID to keep
PID to keep
Steps to do volumetric mesh
- Do right click on PID name and choose remesh option from drop box.
- After clicking on remesh a pop-up-box will appear which will contain ifferent type of meshing techniques. Choose tetra CFD as we are doing CFD operation.
Volumetric mesh done
Cross sectional view of volumetric mesh
Link to geometry
https://drive.google.com/file/d/1EesTZVYDiNtkmgTHvt3kNAJ8PGpaqWQ0/view?usp=sharing
CONCLUSION
- Got familiar with more complicated and advance ANSA tools
- Learnt about volumetric meshing along with 2D meshing.
- Selection of volumes for volumetric meshing
- Creating hot points to convert complex missing parts into simple ones