[David Sauter]

Hi

I am using AutoGrid5 9.1-2 to create a mesh of the cavities of an axial turbine. I need all the blocks inside each cavity to have a matching connection. In the spanwise and streamwise direction I can enforce this manually setting an equal number of points at adjacent segments.
However, at some interfaces, the blocks are not matching in the azimuthal direction because of a different clustering of the adjacent faces. I made the observation that this is the case between the two blocks where the cavity inlet is matching the channel. (See attached picture. The problem occurs at the interface indicated by the yellow line).

I figured that the problem is because the direction of the segments at the channel matching connection (green arrows) are pointing in the same direction. In the cases where they are pointing away from each other, the problem doesn't occur.
So my question is: Is there a way to change the segment orientation in order to get the green arrows to point away from each other at every channel connection interface? Or is there another way to enforce a matching azimuthal clustering on all blocks in the cavity?

I am fairly new to AutoGrid. (In fact, I am new to mesh generation mesh generation in general.) So any help would be greatly appreciated.

[Hamidzoka]

Dear David;
I think the current block distribution needs to be modified. there are some improperly defined blocks with highly distorted elements that substantially lowers the quality of meshes.
It is recommended to use only one block at channel connection edges. this will solve the problem.
one more point is that: "use the lowest possible number of blocks"

Regards

[David Sauter]

Dear Hamidzoka

Thank you very much for your quick answer. The way you recommended to proceed makes sense to me.

However, modifying the blocks manually led me to another issue. (Which I hope is not too basic for this thread). The blocks I added manually are not automatically mapped at the outer segments any more (i.e. at the cavity wall and at the channel connection). How can I manually map at least the channel connection in order to achieve a matching connection?
I already created Z-constant lines, but this did not resolve the issue.
I have imported the cavity geometry from an .igs file and applied the automatic domain definition.

Best regards

[Hamidzoka]

Dear David;
Normally adding z-constant lines provides a matching connection between the two. But it is not mandatory and non-matching connection (i.e. using no z-constant line) is still reasonable. one important issue here is that blocks are completely mapped to the geometry of the cavity.
Maybe I can help if I have the AG files.

regards

[David Sauter]

Dear Hamidzoka

Sorry for the late reply.

Mapping the blocks to the geometry by inserting vertices did solve that issue. However, with manual blocking, AutoGrid did not create a correct 3D mesh any more. Therefore we had to go back to automatic blocking. We then solved the problem of the non-matching patches in the cavity 3D mesh in an other manner: We opened the mesh in IGG and manually corrected the clustering at the segments that were non-matching. I consider the issue resolved now.

Thank you again for your help.

Best regards,
David