IGG connecting multiple blocks to a common interface for Volute meshing

Hi Joseph, 
Based on these images I am wondering whether the patches on the two sides of the full non-matching connection are on a common surface at the location where they should be connected? I suspect that using the extrusion method that is not the case. When computing the full non-matching connection you'll probably see both sides will be treated as a solid wall. Or the space in between the patches is so small that it will treat it as a full non-matching connection but it introduces errors. 

Best regards,
Colinda

I agree with Colinda. It seems that the edges are snapped onto a surface different than the one you want to use as a connection between the two mesh blocks. I would also add that the mesh you are going to generate is going to be extremely skewed near the tongue. Meshing a volute with a structured grid is quite laborious; it's always important to sketch the mesh before starting the meshing itself. 

For example, a good mesh quality could be achieved using this approach (but it may require some work):

Hi Colinda,

Thanks for the reply. You were right! Using the extrusion is this manner does not guarantee a common touching surface and renders the method incorrect. I'd been trying a different approach since the initial post: I inserted a block at the cutwater region, seen outlined in red in image 1, and created three internal faces. This resulted in four regions marked 1,2,3 and 4 below. I then changed the limits of the extrusion to cover only the orange face of block four, in a similar manner to the volute tut. This allowed me extrude only that face or orange patch of region 4. Going clockwise, I then extruded the consecutive blocks

When I neared the cutwater after going around, I extruded the face that covers region 1,2,3&4 from the relevant side(seen in blue): 

I then selected the two faces which touch each other, and set them to full non matching:

Only the outlet tube remained. I think I divided the patch on region 1,2,3,4 in the Patch selector menu to create a patch for only the circular region 1. Then I selected that patch and extruded it:

The final mesh is seen below:

I am still trying to resolve orthogonality issues around the fillets but thats my progress so far

Hi Domen,

Thanks for the useful suggestion and the example, I will definitely do so going forward. You are also right about the connection matter. I remember seeing a presentation that Numeca did where they made a parametric volute model using structured meshing and have new found respect for that process . I think it was called :Simulation driven optimization for advanced turbocharger design.

You are right about skewness at the tongue . The small fillets around the tongue region also presented issues to properly capture. 
I have been puzzling with finding a better block arrangement around this area. I was thinking about using more internal faces around region 2 but I suspect the triangular like taper caused by the filler will still render skew cells. I would really appreciate any alternative ideas if you may have. At worst case, I could omit the fillets but I would like to preserve the original geometry as far as possible

I would split the domain into three parts, then use interfaces (FNMB in Igg's lingo) to connect the three regions.

1 outlet conical geometry

2 around the tongue

3 scroll

At the tongue, we would use something like a "C" configuration. Two blocks follow the tongue, other two are placed at the throat. 

If you place well your blocks and grid points, the two sides of the interface will be slightly different mesh-wise, nothing that Fine Turbo can't deal with. 

This configuration will work well once you begin to refine the mesh along the boundaries. Anyway, it's quite a lot of work. If an unstructured mesh is possible, it's definitely a no-brainer.