Learning Forum

[ari003]

I currently faced a situation where I am unable to figure out the difference between Global and local element size.

Actually I am meshing it to use it in fluent and the body is 2D consisting of a single face( bounding domain with an airfoil). While I was specifying the element size, I was selecting the sizing option by right-clicking on the mesh, selecting the only surface and putting the value(0.008m) there and proceeding with the generate mesh. There I was skipping the Global element size which was made to default(0.205m). Now my doubt is which size will system consider for meshing and what if I put the Global and Local element size same value?

Will be very helpful if I get a response.

 

[peteroznewman]

Local controls override Global controls.

Global controls apply to entities that have no other controls applied.

[ari003]

I checked with both condition.
First without any local sizing(only Global) and then with local sizing.
In both case the aspect ratio and skewness obtained are different.
Any idea on this?

[peteroznewman]

I expect a mesh with a .205 m size to have different aspect ratio and skewness than a mesh with a .008 m size on the same geometry. That fact is not interesting to me.

An interesting question is what mesh controls will create high quality elements on a given geometry, and how can that geometry be sliced to improve the element quality and get a good inflation layer on the boundary that is a wall.

[ari003]

You didnt get what I said in my previous comment though.
I tried first with Global element size as 0.008 and then in my second attempt I have given a local element size as 0.008 and kept the global element size as default. As u said that the local will override which happened in the second case but the mesh quality (aspect ratio and skewness) changed which I didnt expect.

[peteroznewman]

You applied a size control to a face, but there are edges too.   What happens if you assign a local size control to all the edges as a second control?  I don't know what to expect, but I don't care either.  I just use the mesh controls to get good quality elements.