[Ema40]

Hello.

In some zones of the domain the mesh is not good; it is possible to modify it locally, for example by smoothing or topology optimization?

What do I have to do to change it only where I want?

There is a way do make fluent to highlight zones where the mesh quality need improvements?

Thank you

[Kapi]

Hi Ema!

If you know where the mesh isn't up to the mark, you may use 'sizing' function to restrict the mesh how you want it to be.

You can use sphere of influence to give a particular region where you want good mesh in case you are not able to select edge,face or body in that region.

Using "Behavior" either Soft or hard and 'Bias type' depending upon geometry, you can make mesh fine and coarse.

I am not sure if you can highlight where mesh is bad in fluent but you can surely check the quality of mesh like skewness, aspect ratio and other things in Meshing under 'Statistics', this should give you a clear understanding of where mesh isn't good.

Hope it helps.

Cheers
Kapi

[Ema40]

Thank you very much.
My problem is that in Statistic there are some cells with aspect ratio=36 and I want to know where they are, to modify them.
Do you know how to do?
Thank you

[Kapi]

Hi Ema!

Once you select Aspect Ratio in Statistics, it opens up Mesh Metrics bar chart under the display window. This bar chart shows all the elements of mesh with respect to thr Aspect Ratio. You may click on the bar which shows Apsect Ratio of 36 and these elements will be displayed in the window. You may then mesh these elements with finer mesh with help of sizing function.

Please find attached pic which shows the bar chart and display of higher aspect ratio elements!

Hope this Helps

Cheers
Kapi

[Ema40]

Thank you very much! I have understood.

I have reduced successfully the average aspect ratio, but in some zones it remains at about 4, even changing the sizing.

[Kapi]

Aspect Ratio of 4 or less can be termed as good depending on mesh and geometry.
They will not be categorized at bad elements imo.

[Ema40]

ok. But an element with aspect ratio 4 means that there is an edge with a length four times bigger than an other edge in the same cell. Isn't it too bad?The cell will be too elongated.
What is the maximum aspect ratio still defined as good?
In the Workbench it says me "error updating cell mesh in System Fluid Flow"; what does it mean? Despite this message, I can start the simulation.
Thank you very much for your kindness

[Kapi]

Hi Ema,

As per Ansys Help the Aspect Ratio can range between 0.5 to 20, after 20 it mite disturb or change analysis but within the given range the mesh is suppose to be good.
The best possible quad and tri elements is with aspect ratio of 1 but with inflation and type of geometry it is not possible everytime to have all elements with Aspect Ratio 1.
You can read Help section to find more about Aspect Ratio and how they are derived.
Also higher Aspect Ratio (20+) can be considered good for 3D Geometry,type of flow and placement of the first node in near-wall mesh(Y+).

Hope It helps,

CHeers
Kapi

[Ema40]

Thank you very much for your help!