Relation between meshing parameters to avoid stair stepping

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  • Last Post 22 March 2019
CatiaV5 posted this 17 March 2019

Hi there,

 

I am trying to mesh a delta wing in ansys mesher. I have created a body of influence around the body and used the following paramaters

General Mesh settings:

Fluent Mesh

Capture Curvature No

Capture Proximity No

Mesh Defeaturing No

Max Angle 180deg

max height over base 0.7

 

body of influence:

element size: 5e-3m

 

face sizing (on the wing):
element size: 1e-3m

capture curvature no

capture proximity no

 

Inflation (on the wing):
1st layer height: 1e-6m
Number of layers: 45
growth ratio: 1.17

 

With these parameters I get a mesh without any warnings. However, it results in a rather large mesh. In order to bring the element number down I would like to increase my element size in the body off influence. When changing it to 8e-3 I suddenly get stair stepping. I was wondering why I get stair stepping when changing the body of influence element size and what can I do to avoid stair stepping? Is there a way for me to know how face sizing, inflation layer and body of influence sizing have to relate to each other? 

The trouble is that I need a lot of elements on the wing surface so increasing the face sizing on the wing is not an option. I can increase or decrease the 1st layer height but will need to change the number of layers accordingly. 

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kkanade posted this 19 March 2019

can you please insert image of your geometry and boi. 

is your boi covering entire wing body?

in face sizing, can you please use 'hard' behaviour. 

CatiaV5 posted this 20 March 2019

Sure, find below different views of the boi with the geometry. I use a half model and apply symmetry boundary condition in case this isn't clear from the image. I figured that when I change the growth rate to 1.2 I get it meshed but I'm still unclear as to what the relation is. I will try one with "hard" behaviour and my previous settings which resulted in the warning too.

 

Btw is there any recommendation for the "maximum height over base" setting?

 

And thank you for the quick reply on this post!

 

 

kkanade posted this 21 March 2019

which one is boi? top or bottom?

why domain it is divided into top and bottom?

can you please single domain instead of top and bottom?

CatiaV5 posted this 21 March 2019

What you see is the BoI. The domain is 20 chord lengths. I couldn't depict it otherwise you would not have seen the geometry. The domain is one body. The body of influence are two bodies as depicted in the picture. Shall I merge them into one? 

I also get a funny inflation layer. After around 20 layers or so it stops growing but adds smaller layers (see picture). Thus, I'm not capturing the boundary layer. Is there anything I can do to avoid this? I have tried using total thickness but getting a collision warning and the mesher stops without creating any inflation layer

CatiaV5 posted this 21 March 2019

I have tried to use a boi as a single domain without success. I decided to use a geometric type of inflation which gives me better inflation layers but stair stepping which is so severe that the layers around the tip totally collapse

kkanade posted this 22 March 2019

please use single boi. 

also i can not understand anything in the latest image you have posted. 

 

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kkanade posted this 22 March 2019

please use single boi. 

also i can not understand anything in the latest image you have posted. 

 

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Be efficient - As our community grows it is becoming more likely that you are not the first to ask this question. Please search before creating a new post. 

Be clear - Provide supporting screenshots, error messages, and background information. No simulation files will be opened by ANSYS support engineers. 

Be precise  - Please use the right tags to help our engineers find your question.

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Be helpful - Please help our community grow by answering other's questions and telling your academic colleagues about this resource.

 

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