[ANSYS Meshing] Triangle method and inflation quads of airfoil

Zeyadhesham · December 30, 2020, 18:50

I have this problem that is messing with my skewness making it 0.98 and I found out after looking at the skewness metric that all the triangles around the airfoil after the inflation layers are the ones ruining it, and I have no idea how to fix it.
Thank you in advance!

LoGaL · December 31, 2020, 05:38

To me, you get bad cells because the triangles transition too fast frm being very big to being very small.

How are you setting this inflation layer? it has growth rate 1 as far as I can see. Are you assigning first layer height?

Zeyadhesham · December 31, 2020, 09:44

Thank you for replying!
Yes it has a first layer thickness and I set it to 1.5 growth rate, and someone told me to meddle with the expansion rate but I cant find that option. What do you suggest I do to solve that transition ?

LoGaL · December 31, 2020, 13:44

Wait wait, there are two growth rates, one is the general mesh growth rate, the other one is the one of the inflation layer. It is the ratio of the volumes of two adjacent cells.

In your inflation layer, you clearly have a growth rate of 1: the mesh element size is not changing at all layer by layer.
Then, there's the transition to tetra elements, I think the growth rate is there too big and it gives you bad elements. Probably the mesher is trying it's best to reach the size of your elements in the inflation layer.
Never heard of 1.5 growth rate in the inflation layer. It should be between 1.1 and 1.2, for your application i think 1.2 is ok. Try to set your inflation layer to 15-20 elements, give him a growth rate of 1.2 and set first layer height. See what happens.

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December 31, 2020, 05:38		#2
LoGaL Senior Member Lorenzo Galieti Join Date: Mar 2018 Posts: 373 Rep Power: 12	To me, you get bad cells because the triangles transition too fast frm being very big to being very small. How are you setting this inflation layer? it has growth rate 1 as far as I can see. Are you assigning first layer height?

December 31, 2020, 09:44		#3
Zeyadhesham New Member Zeyad Hesham Join Date: Nov 2020 Posts: 3 Rep Power: 5	Thank you for replying! Yes it has a first layer thickness and I set it to 1.5 growth rate, and someone told me to meddle with the expansion rate but I cant find that option. What do you suggest I do to solve that transition ?

December 31, 2020, 13:44		#4
LoGaL Senior Member Lorenzo Galieti Join Date: Mar 2018 Posts: 373 Rep Power: 12	Wait wait, there are two growth rates, one is the general mesh growth rate, the other one is the one of the inflation layer. It is the ratio of the volumes of two adjacent cells. In your inflation layer, you clearly have a growth rate of 1: the mesh element size is not changing at all layer by layer. Then, there's the transition to tetra elements, I think the growth rate is there too big and it gives you bad elements. Probably the mesher is trying it's best to reach the size of your elements in the inflation layer. Never heard of 1.5 growth rate in the inflation layer. It should be between 1.1 and 1.2, for your application i think 1.2 is ok. Try to set your inflation layer to 15-20 elements, give him a growth rate of 1.2 and set first layer height. See what happens.