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-   -   [ICEM] Pipe 90 elbow joint meshing issue (http://www.cfd-online.com/Forums/ansys-meshing/113103-pipe-90-elbow-joint-meshing-issue.html)

sihaqqi February 12, 2013 09:43

Pipe 90 elbow joint meshing issue
 
2 Attachment(s)
Hi

I am using ICEM CFD to make a 90 elbow mitre joint. I could not make a perfect curve and surface at the elbow so I have got two cylinders intersect each other at 90.

Now the issue is: while associating my block edges with curves at the elbow junction, one block edge is common for two curves, one is the intersecting curve and other solid side of the elbow, meaning I have 7 edges for two curves instead of 8. Can anyone advise what should I do to associate both curves with edges properly.

Also, the curve of the elbow which is a wall, should I make it part of the downstream pipe or make it a face with a separate part name as flow is diverting from vertical to horizontal pipe here. Green pipe is upstream whereas red is downstream.

During O-grid, should I select the solid wall of the elbow as one of the faces or not. Solid wall with poor mesh is shown in attach image.

I shall appreciate your response.

Regards

Far February 12, 2013 10:32

this is wrong

sihaqqi February 12, 2013 19:20

I know thats why I have posted it. Could you please advise how should I do it

jrunsten February 13, 2013 02:45

Is this what you want to do?

http://i.imgur.com/XfUasOU.png

http://i.imgur.com/3yPPKM6.png

http://i.imgur.com/ECkN3Kg.png

sihaqqi February 13, 2013 09:52

Josef,

I think this should be it. After Far's response, I tried to make a 2d elbow but I cannot block mesh properly and still trying to find out method to extrude. I am a beginner of Ansys ICEM CFD and have enrolled in MS program by research. Can you please send me the steps to make it, and above all the intesection circle is what I cannot properly make. At 45 degrees, it does not stay a circle. I shall be very grateful so that I can practice making it. Thanks for going through these efforts.

Regards

jrunsten February 13, 2013 10:07

ICEM isn't really your ideal geometry tool. I made mine in Designmodeler and imported it into ICEM. Surely you must have som CAD tool at your school.

Here you can get the files to get the mesh I posted above:

https://www.dropbox.com/s/pkm7h1a6ge02gj4/Elbow.rar

sihaqqi February 15, 2013 08:37

Hello Josef

Many thanks however my geometry has different dimensions. I have got Ansys DesignModeler with me and I am trying to work out how to draw on it. I have created two cylinders one sitting on top of each other. Can you please advise how I can trim to get exact 45 joint. I have tried to make two circles perpendicular to each other and tried to trim but that is not working.When I make two cylinders perpendicular to each other, trim or chamfer commands do not work. Can you possible advise some basic steps of construction of the model. I have tried to look for some tutorials and I am beginning to get a feel of the software but since I am not an expert, I am getting stuck. My geometry is 72.54mm diameter and 1200mm vertical and 4000mm horizontal but I do not want you to make again as I have to change geometry diameters for data comparison so it is better I learn how to make it. Also on ICEM CFD, I can get a hollow cylinder directly but here do you think I can just use the solid cylinder as "Fluid" and running it in Fluent. And, how do you import it in ICEM CFD.

Thanks for your positive response.

Regards

jrunsten February 15, 2013 08:46

Create > Slice > By Surface:

http://i.imgur.com/NWl96bq.png

Create > Body Operation > Delete:

http://i.imgur.com/PyjdLwr.png

Create > Boolean > Unite: All bodies

This should leave you with a single bended pipe

sihaqqi February 15, 2013 23:00

Many thanks Josef. You have solved a great problem.

Regards

sihaqqi April 16, 2013 03:36

Hi Josef

In my geometry, I having a small problem. When I make circles and extrude, I get this geometry but I can only define number of nodes at circle edges and junction curve. I want to define number of nodes longitudinally along the pipe but since using extrude command, I do not get longitudinal edges, I cannot do it. With defining number of nodes at edges, I can refine my mesh as much as possible but if I want to control refining making dense at junction and coarse along the length, it does not work to save computation time.

I have tried to draw the same geometry by sketching two lines perpendicular to each other but with revolve command, I can only draw one cylinder. When I want to draw second cylinder, it does not revolve. Can you please help again?

Regards

jrunsten April 16, 2013 03:47

Aren't you meshing in ICEM? Then you set the sizing on the block edges, not geometric entities?

sihaqqi April 16, 2013 06:25

No I do not know ICEM. I am using Ansys Workbench and in it, we first draw in DesignModeler and then use AnsysMeshing. I have done some tutorials but now I am stuck in this node numbering issue. If this problem is resolved, a major hurdle will be over.

jrunsten April 16, 2013 07:08

Well, for example in the image i posted above. If you slice the geometry in the XZ plane, you would get edges in that direction, but also a split volume.

You could do this..

Concept > Split Edges: Split the circular edges at the end of the straights so that you get points in the joints.

http://i.imgur.com/c98W0vR.png

Then Tools > Face Split: Use Split type "By points and edges" and use the points you created in the edge splits. You will then split the face you choose along the line between these two points.

http://i.imgur.com/UgbVYhg.png

Im sure there are other ways, but this will get you an edge, if that is what you want.

sihaqqi April 16, 2013 23:04

thanks Josef

Job done

Regards

sihaqqi May 31, 2013 05:56

2 Attachment(s)
Hello Josef

Many thanks for your cooperation in the past. Without your help I could not have gone this far with my project. However I am now stuck. Previously I did my CFD on the geometry and but now I have to check vibration on structure. What I have done is I have again drawn my geometry, this time a L-shaped pipe junction 6.35mm thick wall.

I have adopted two methods, I draw two circles for a cylinder which would make one sketch and then extrude.

When I apply the same rules of construction as you advised earlier it does not work. After both parts have intersected, I have tried different options. Sometimes I get fully enclosed junction from which flow cannot pass as shown in fig 1 and sometimes the whole thing goes out. I have tried to draw edges on faces and then surfaces from edges. I have also used thickness as 6.35 and o both. But somehow exact thing is not appearing. Can you again help as I shall have to again doo CFD and then model it for FSI and Modal Analysis.

I have adopted two ways, one in which I have modeled two circles together and extruded a length out of it. the other I have made same way but getting the right intersection at 90 is a problem.

second I have made inside fluid first and in the structural geometry, I have "add frozen" Is this method correct. Only reason I am confused is that in in this method, you can view liquid separately but when it comes to solid, you see it appearing in the complete section as if it is complete solid whereas in the first approach both are visible individually. Do results change

Secondly is there any utility in Fluent with which I can suppress the structural part and calculate on fluid only. When I want to do structural, I would like to suppress fluid part so I can do FSI.

Regards
Imad

jrunsten May 31, 2013 06:55

Can you share your DM file (.agdb) ?

sihaqqi May 31, 2013 08:56

3 Attachment(s)
Quote:

Originally Posted by sihaqqi (Post 421090)
thanks Josef

Job done

Regards

Quote:

Originally Posted by jrunsten (Post 431181)
Can you share your DM file (.agdb) ?

AGDB is not approved extension to be appended here by cfdonline forum. If you can send me your email id, I can send it to you. Internal faces in fig 3, fig 4, and external in fig 5 need to be removed. Also if you can respond to my other queries in my post and send me some tutorials on FSI both 1-way and 2-way, it would be great.

Regards

jrunsten May 31, 2013 09:40

Simpler way to create the bend:

http://i.imgur.com/l8BgVGT.png

sihaqqi May 31, 2013 09:52

thanks but since I am not as expert as you are. can you kindly advise commands for the first two slices,

how can I slice centre
how should I slice at 45 degrees

regards

jrunsten May 31, 2013 09:55

Center: Create a scetch on the end of the pipe. Extrude it through the pipe.
45: Create a new plane at the other end. Move it 1 diameter into the pipe. Rotate it 45 degrees. Then slice using the plane.


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