[thinktank]

Hii all..

I am trying to mesh a slightly complicated structure using hexa using ICEM CFD. I have been able to successfully mesh the structure, however unfortunately the structure appears to have some peculariaties due to which I cannot figure how to reduce the skewness of the meshes. I have put up an illustration of the problem here.
The picture below is a 2-dimensional view of the mesh along with the geometry of the part of the structure involved in the problem I am facing.







To capture the tertiary channel, I used a simple blocking technique, as shown above, however it turned out that due to the sudden contraction of the channel, highly skewed meshes are formed. I was able to get the simulations running in Fluent, however I think due to this high skewness (Tgrid skewness > .95) in region surrounding the contraction, the error in the continuity equations never go below .3, as a result of which I never get a converged solution. Further the velocities come out to be around 10^4 times higher than in the outer regions, which doesn’t seem physically correct. This is why I think there is some problem with the mesh.
Since the surface of channel has a elliptical shape, I thought an Ogrid might be suitable, so I tried an ogrid, while keeping the top and bottom surface fixed as shown below.
I split the central box in the O-grid to obtain a better uniformity in the mesh size. This is the mesh distribution on the bottom surface:

While the Tgrid skewness in the region surrounding the expansion reduced significantly, the skewness in a separate region increased dramatically to> .95.


The second problem I am facing is in the skewness in the longer section of the tertiary channel connecting the primary and the secondary. Due to the high rate of expansion, this too gives rise to a highly skewed mesh.


So I was wondering if there is some technique to reduce the skewness of the mesh which I can apply here. It would be great if somebody could give some advice.

Thanks