3D Hybrid Mesh of a Train
 

Hi,
I have been trying to create mesh on a 3D train using both structured and unstructured mesh in ICEM CFD. I'm planning to create a structured mesh on its body and unstructured mesh for the underbody parts (bogie, cowcatcher, etc).

I sucessfully created the structured mesh for the train body by splitting the blocks, associating the vertex to point, and vertex to edge. However, I don't have any idea on creating the unstructured mesh for its underbody part. I have tried using 2D surface blocking and multizone fill for the underbody parts, just like the HVAC ICEM tutorial, but the process deleted my structured block and only mesh my 2D underbody surface.



Can anyone suggest me on how to do this hybrid mesh of a structured upper body train and unstructured underbody train?
Thanks in advance.


I attached some images too for a clearer desc.

Hi Tim,

have you had a chance to do the tutorials explaining (for a pipe) how to create a hybrid mesh? You'll need to follow a specific order of operations to get the final mesh.

If you have to deal with multiple topologies (in your case: fully 3D, and 2D surface blocking) you likely have to use two different project files, one for each and then merge the exported mesh at in a project file.
I'd suggest to start with the structured mesh. Export it. Continue from there to create the truck's mesh in another file. At the end load both mesh domains into one file and deal with interface conformance.

Moreover, you might like the "Simon's Tips and Tricks" Guide to be found in the sticky thread of this subforum.

Best regards,
Sebastian

Hi Sebastian, thanks for the reply.


I haven't tried the hybrid mesh for pipe that you mentioned since I don't have the geometry of the pipe. I have read the tutorial of the pipe hybrid mesh, but I don't understand the term "interfaces" that is separating the three region of the pipe.
Do we need an interface between the connection of different type of mesh? Is it like a surface between structured and unstructured mesh?



The Tips and tricks by Simon that you suggested was good. It helped me understand several things. However, I don't understand the tips to merge surfaces as suggested by Simon. What does it mean by surface parts share a perimeter and must intersect each other? (I will attach the image below)


Regards,
Tim.

These are just surfaces in the geometry - but in a different part.
You can easily create this geometry yourself. Use Build topology at the end to make sure your geometry is watertight.
It means you need to have a curve/surface which is part of both objects.

You can color curves on how many surfaces are connected to them.
In the default color scheme, red curves mean they are connected to two surfaces, blue means three or more surfaces.
And yellow means these are free ends (only on surface attached).
For a water tight geometry you must not have any holes of yellow edges.
The Build Topology feature should be helpful in many cases.


After you create the block and cylinder with coincidental top surfaces you can use the build topology tool to intersect the geometries. (There is a feature in 'create surfaces' to build primitives such as blocks and cylinders.)
The circle top surface of the cylinder will then be imprinted into the square top surface. the perimeter curve (the circle) will then likely be blue because it will be part of three surfaces.



Best,
Sebastian

Hi Sebastian thanks for your suggestion,
I have created the interface between the hexa and tetra mesh by creating a surface and intersecting them using the build topology just as you have suggested. I have also followed the ICEM tutorial about hybrid mesh to create the tetra and hexa mesh in my train model that I'm working on.
However, I'm still receiving an error when I try to merge the mesh. The error message is:
I am trying to include edge 9181 9187 but vertex 9181 isn't even in the region 1
error including edge 9181 9187
could not include quad
Can you please tell me how to resolve the problem?


Thanks,
Tim