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-   -   Having issues Splitting (http://www.cfd-online.com/Forums/star-ccm/100308-having-issues-splitting.html)

raleigh747 April 23, 2012 19:27

Having issues Splitting
 
Howdy all.

Background:

I'm having a bit of trouble getting a part to split. I have a hollow cylinder imported from SolidWorks. I generated a block using Star CCM+ (v7.02) with the cylinder sticking part of the way out. I split the block using "split by angle" into 6 surfaces and made the surface with the tube through it a part (let's call it the base).

Issue:

Now what I want to do is split the base so that the surface of the base outside the tube is a separate part/region from what's inside the tube in order to assign them different boundary conditions. It was my understanding that this was possible but I can't seem to get it to work.

I've tried all the other split commands but can't get it to work. Any ideas? Thanks!

ryancoe April 26, 2012 10:45

While it may be possible for you to do this within Star-CCM (not sure if I exactly understand the geometry), you could certainly just go back to SolidWorks and create a version of body that has distinct parts where you need them.

Star-CCM has been improving its geometry manipulation and meshing capabilities over the years, but I still find that its best to do as much preparation as possible in the CAD software before importing.

LuckyTran April 27, 2012 01:42

Quote:

Originally Posted by raleigh747 (Post 356518)
Howdy all.

Background:

I'm having a bit of trouble getting a part to split. I have a hollow cylinder imported from SolidWorks. I generated a block using Star CCM+ (v7.02) with the cylinder sticking part of the way out. I split the block using "split by angle" into 6 surfaces and made the surface with the tube through it a part (let's call it the base).

Issue:

Now what I want to do is split the base so that the surface of the base outside the tube is a separate part/region from what's inside the tube in order to assign them different boundary conditions. It was my understanding that this was possible but I can't seem to get it to work.

I've tried all the other split commands but can't get it to work. Any ideas? Thanks!

create a feature curve on the surface corresponding to how you want to split it, and then split the surface using the feature curve. Haven't used Star-CCM in awhile so I cannot give step by step details but I know this will work

rwryne April 27, 2012 08:33

As ryancoe alluded to, its hard to visualize this without a picture. Can you post one?

abdul099 April 28, 2012 07:52

Either you can try a Boolean -> Intersect with your parts (don't put the surfaces of the block with the tube through it in a separate part but just use the whole part).

Or even more complicated, but way more powerful is to go to the surface repair with both parts at the same time. Select both parts, right-click, choose surface repair. Then choose "intersect faces" from the most top menu, select the first set of faces to intersect (let's say the base) by double-clicking, assign it to the first set. Then do the same with the second set and hit "intersect". That will intersect the faces and create a feature curve along the intersection edge.
Now you can select each of the faces separately and assign them to a new part surface or delete them. Depending on what you try to achieve, you must do something since you would have non-manifold edges when doing nothing but the intersect.

raleigh747 April 30, 2012 15:07

1 Attachment(s)
Attachment 12815

Shown is the cube prior to splitting the cube's surfaces. The cylinder portion of my assembly is sticking out the side as shown.

I can split the box in to 6 surfaces and set the face that the cylinder intersects as a separate part (the base). Now, I want to split the base using the cylinder such that when I make the base parts into regions, I can assign different boundary conditions to the base parts inside and outside the cylinder.

abdul099 April 30, 2012 15:13

When it should be just one body (a block with an inlet and outlet boundary), just follow my second suggestion.
When it should be two bodies (e.g. a simple heat exchanger model), you should do a Boolean -> Subtract and use the resulting body as one of the input bodies for the regions and the cylinder as the second one.

raleigh747 April 30, 2012 19:29

@Abdul

I can't seem to get the Boolean Subtract to work. When I use the base or cube as the main part, one of my shapes is "not closed or a manifold." The other way crashes the server for some reason.

When I do your first suggestion, I get the two parts selected and hit "intersect" and the output says it intersects the faces and displays the outline of the intersection but I'm not sure how to use that intersection or find it once it's been "made." It doesn't show up under the Block or Assembly curves.

But I definitely appreciate your help!

abdul099 May 1, 2012 03:11

Have you checked your input parts to be error free? If not, check them one by one. Afterwards the Boolean subtract should work. If it still doesn't work, we need to investigate further.

The use of the intersection curve generated in surface repair is quite easy, but there are (again) several options what you can do.

First, needed for both options: Right after doing the intersect, make sure to mark the intersected edges as feature curve (hit f in surface repair or press the appropriate button). Now the edges should be marked with a thick line.

Now you can either leave the surface repair mode. You will see some feature curve named "Surface repair edges" or something similar. I don't have ccm+ running right now, therefore I'm not fully sure about the name. This feature curve can be used to split the boundary by using "split by feature curve".

Or you can stay in the surface repair and hide all cylinder faces. Then you double-click inside the circular feature curve (make sure, selection mode is set to faces). That should mark all the faces belonging to the block and being inside of the cylinder. Now you can assign them to a new part surface. In the menu on the left, near the selection mode ish. I think a little below the line where you can choose to display or hide faces.

Again, I'm not too sure where exactly you will find the option. So just have a look and see if you can find it. If not, let me know, I can do some screenshots today evening.

But be aware, both methods will give different results. You can achieve whatever I can imagine you might want to achieve with both methods, but it would help to know what you finally want. Do you want as result only one part with split surfaces? Or do you want to parts, one enclosing the other one?

raleigh747 May 1, 2012 14:13

@Abdul

I want to assign the outer part of the base and the cylinder the wall boundary condition and give the section of the base inside the cylinder a boundary condition that will allow me to determine what % of aerosol particles actually pass by the plane. So I need to maintain the part of the base inside the cylinder OR generate a thin part in SolidWorks on the inside of the of the cylinder and line the base of the box up with it.

raleigh747 May 1, 2012 16:47

@Abdul,

I got the Surface Repair tool to work. It did exactly what I wanted and, hopefully, that's what I need and ccm+ continues to cooperate. Thanks for all your help!


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