[jimbean]

Hi all,

I am new to Gridgen and wanta to mesh an open channel with many solid cylinders in it. Please the sketch below, since i've no idea how to upload an image.

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。。。
。。。
。。。

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Two dash lines are channel boundary.
Small circles are cylinders. Flow is from left to right.

Does any one have any idea how to exclude the cylinders out of the mesh?

Thank you.

[Hybrid]

Do you want to make structured or unstructured meshing?

First select the outer edge (i.e. channel),..> save edge
then select circle --> save edges, its orientation must be opposite to the outer edge(chanel).
then other circle --> save edge, having the same orientation as first circle.

and so on. when completed..apply

Check tutorial :Pipe in a Cube

[jdrch]

Originally Posted by jimbean

Does any one have any idea how to exclude the cylinders out of the mesh?

I've never used Gridgen, but generally you mesh the flow surfaces first (including the outer surfaces of your cylinders) in a 2D mesh, and then generate a volume mesh from that. Ensure your element normals point outwards towards the wall from the cylinder surfaces and inwards towards the cylinders from the wall, as many meshing packages grow 3D volume meshes in the direction of the element normals.

[jchawner]

Hello Zhengbing:

Let's assume you're making a 2D mesh. If the mesh is unstructured as Ali illustrated, you'll be creating a single domain with multiple edges. The first edge is the outer loop and each cylinder is an additional inner edge. The only thing to keep in mind is that the direction of each inner edge must be opposite the direction of the outer edge.

If the grid is structured, you'll need to decide on what type of topology to use and you have many, many choices for doing that. In other words, your final grid will consist of many domains, not just one like the unstructured case.

If you have other questions don't hesitate to contact our tech support engineers at support@pointwise.com.

[jimbean]

Thank you, all.

I wanted to mesh the field with structured grid.

With these explanation you gave, i should divide the whole field with many subdivisions, which exclude the cylinders, and then mesh every subdivision with the structured grid.

Does this make sense?

[jchawner]

Yes, your approach makes sense. You have to decide which type of block topology to use. For example, O-grids around the cylinders or H-grids everywhere. It's your choice and you have many options.

[Hybrid]

Is there any plan of Pointwise developers to include "Automatic O-Grid" like in Ansys ICEM or butterfly Mesh (automated).

[jchawner]

I seem to recall that we wrote a Glyph script that converts H-grids to butterfly topology. It might be on our Glyph Script Exchange website.

[jimbean]

TO Ali,

The procedures you said below are for Gridgen or Pointwise
I haven't found something about saving edge in Gridgen. I am using Gridge V15.

Originally Posted by Hybrid

First select the outer edge (i.e. channel),..> save edge
then select circle --> save edges, its orientation must be opposite to the outer edge(chanel).
then other circle --> save edge, having the same orientation as first circle.

and so on. when completed..apply

Check tutorial :Pipe in a Cube

[Hybrid]

To John Chawner;

Originally Posted by jchawner

I seem to recall that we wrote a Glyph script that converts H-grids to butterfly topology. It might be on our Glyph Script Exchange website.

That script is for Gridgen, not working in Pointwise.



To Zhengbing;

Originally Posted by jimbean

The procedures you said below are for Gridgen or Pointwise
I haven't found something about saving edge in Gridgen. I am using Gridgen V15.

This is in Pointwise.

[jimbean]

Thank you. Ali