[zaki21]

Hi, yes I have looked at all the other posts regarding negative volumes but I couldn't figure out how to fix my problem.

How do i fix the hub layer error.

I attach an image. Please guide me.

[Gert-Jan]

Ask this question in the ANSYS Mesh & Geometry forum

[PabloXX37]

I agree with Gert-Jan that your question might be better directed in the ANSYS Mesh Forum. However here are some aspects that might help you out:

The first thing, judging by the image you posted, is that you don't appear to have a negative volume problem, but rather a problem with your grid orthogonality at the hub. This occurs because some of the elements of your mesh surpass the default tolerances of the program. Therefore it gives you an error message.

That being said, you have two options:

1. Try fixing your mesh at the hub by playing around with the control points of the blocks. In general you should try to get an orthogonality as close to 90 degrees as you can. Good tolerances are normally between [30-150] degrees, and worst case are [10-170]. Just for reference, your worst values are 0.48 and 178 degrees, both out of the ranges that I specified above.

2. Leave the mesh as it is. You only seem to have around 0.1% of the mesh with values out of the tolerances. If you want to eliminate the error you can always modify the tolerance limits to some angles that include your worst case mesh values (so something like [0.4-179] degrees.

Personally I think it's best for you to try and fix your mesh (for the reasons mentioned above). If you want more information on modifying control points and grid quality, I'm sure you'l get a much more thorough response in the ANSYS Mesh & Geometry forum

[Opaque]

Just a notice.

In ANSYS CFX, the "negative volume" message always refers to the control volume's volume, not the element volume. Recall ANSYS CFX uses the dual mesh which is not seen in the viewer.

Though the mesh may look just skewed in the viewer, it may be invalid in the dual.

[zaki21]

Alright great, thank you guys all very much. I fixed the issue. I appreciate it.

[AlexLi_AeroEn]

Originally Posted by PabloXX37

I agree with Gert-Jan that your question might be better directed in the ANSYS Mesh Forum. However here are some aspects that might help you out:

The first thing, judging by the image you posted, is that you don't appear to have a negative volume problem, but rather a problem with your grid orthogonality at the hub. This occurs because some of the elements of your mesh surpass the default tolerances of the program. Therefore it gives you an error message.

That being said, you have two options:

1. Try fixing your mesh at the hub by playing around with the control points of the blocks. In general you should try to get an orthogonality as close to 90 degrees as you can. Good tolerances are normally between [30-150] degrees, and worst case are [10-170]. Just for reference, your worst values are 0.48 and 178 degrees, both out of the ranges that I specified above.

2. Leave the mesh as it is. You only seem to have around 0.1% of the mesh with values out of the tolerances. If you want to eliminate the error you can always modify the tolerance limits to some angles that include your worst case mesh values (so something like [0.4-179] degrees.

Personally I think it's best for you to try and fix your mesh (for the reasons mentioned above). If you want more information on modifying control points and grid quality, I'm sure you'l get a much more thorough response in the ANSYS Mesh & Geometry forum

Thank you for your advice, I also came into similar situation, trying to fix it.