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-   -   [ANSYS Meshing] Meshing time taking too long (https://www.cfd-online.com/Forums/ansys-meshing/235895-meshing-time-taking-too-long.html)

Varshit73 May 4, 2021 12:00

Meshing time taking too long
 
Hey,
Im trying to create a mesh for simple flat plate with ramp model for turbulence modelling. Hence i need a mesh density of around 4 million grid points. But my computer has been at it meshing for 6-7 hours now. I did not expect it to take this long. Not sure why.
I am running on Ansys 19.0 and my pc specs are i7 first gen with 24 gb ram with x64 based OS.

Why is it taking so long? What can i do to remedy this?

evcelica May 4, 2021 21:13

Did you manually mesh anything, or are you making it do an auto mesh?
Auto mesh will take a lot more time than a manual mesh.

Varshit73 May 5, 2021 03:06

I defined a face sizing, body sizing, inflation layers and tetrahedron method. I am not sure if that is auto meshing or manual

evcelica May 5, 2021 17:17

This still sounds like it is mostly auto mesh.
For example, when I make a nice structured mesh, I slice the part into bodies (same part though) and define everything using edge sizing, sweep methods, etc. This means I could tell you exactly how many elements it will end of having when complete, there isn't much the mesher has to figure out on its own. This is what I call "manual meshing". With just loose mesh definitions, the mesher has to figure out how to mesh these parts on its own, and will take much longer.

Varshit73 May 6, 2021 06:34

Ok. so the recommended way is to define everything in small bodies mesh them together and then combine? Would it be better if i used a meshing software like pointwise to develop the mesh entirely? Would it be faster?
Also, if i define all the characteristics of the mesh and then generate in ansys, what would you expect the meshing time if the number of grid points is around 4-5 million? I have attached my model and what i need the mesh to look like
Im a bit new to CFD, so thanks a ton for all the help.

Varshit73 May 6, 2021 06:35

2 Attachment(s)
Quote:

Originally Posted by evcelica (Post 803220)
This still sounds like it is mostly auto mesh.
For example, when I make a nice structured mesh, I slice the part into bodies (same part though) and define everything using edge sizing, sweep methods, etc. This means I could tell you exactly how many elements it will end of having when complete, there isn't much the mesher has to figure out on its own. This is what I call "manual meshing". With just loose mesh definitions, the mesher has to figure out how to mesh these parts on its own, and will take much longer.

Ok. so the recommended way is to define everything in small bodies mesh them together and then combine? Would it be better if i used a meshing software like pointwise to develop the mesh entirely? Would it be faster?
Also, if i define all the characteristics of the mesh and then generate in ansys, what would you expect the meshing time if the number of grid points is around 4-5 million? I have attached my model and what i need the mesh to look like
Im a bit new to CFD, so thanks a ton for all the help.

flotus1 May 6, 2021 07:01

With this fairly simple geometry, creating a block-structured hexahedral mesh in Ansys meshing is pretty straightforward. That should also cut down meshing times to a few minutes.
The general idea is to split your geometry into 3 parts, in a way that each part has 6 rectangular faces. Then apply a few bunching laws on the edges, choose hexa dominant as the meshing method, and that's pretty much it.
There should be many tutorials how to do this on youtube. Search "ansys meshing structured mesh"

This forum might also contain some hints, one example: https://www.cfd-online.com/Forums/an...dral-mesh.html

Varshit73 May 6, 2021 07:07

Quote:

Originally Posted by flotus1 (Post 803268)
With this fairly simple geometry, creating a block-structured hexahedral mesh in Ansys meshing is pretty straightforward. That should also cut down meshing times to a few minutes.
The general idea is to split your geometry into 3 parts, in a way that each part has 6 rectangular faces. Then apply a few bunching laws on the edges, choose hexa dominant as the meshing method, and that's pretty much it.
There should be many tutorials how to do this on youtube. Search "ansys meshing structured mesh"

Okay thats what im gonna do now. Create a structured mesh. But i could not find what bunching laws are? And also i need to create another mesh for this model plus protrusions in the bottom face, should i use the same methodology there too?

Thanks a ton

flotus1 May 6, 2021 07:13

It's been many years since I last used Ansys meshing. So I can't help you with any specifics. Watch a few tutorials, browse the forum for similar topics...

evcelica May 6, 2021 14:57

Is your simulation 3D or 2D?
If 2D you don't need much thickness, just sweep mesh 1 element thick.
Slice into 3 bodies.
"Create part" to make it a multibody part.
use sweep meshing and mapped face meshing
assign number of divisions to lines (the same # of divisions for lines which will be swept through)


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