Learning Forum

[mariamsar]

Hello

I have a pipe with inner and outer diameters as 6 & 10 mm respectively & length of 1 m. I want to add helical ribs to the outer surface of the pipe as that appears on the pictures in DesignModeller? may somebody guide me on how I can do that?

 

[Rob]

Think someone else asked this recently. Have a look at the sweep command & options. 

[mariamsar]

Many thanks for the reply. I cannot find this post may you please send me the link? I will be grateful for that?

Mariam

[peteroznewman]

Here is a post that describes how to draw a helical solid in SpaceClaim.

[mariamsar]

Here is a post that describes how to draw a helical solid in SpaceClaim.

 

Many thanks for the link but I am working with DesignModller and I do not work with SpaceClaim?

[Rob]

Using the power of Google.... 

   

   And that's just the first couple of hits. 

[mariamsar]

Many thanks for the illustrated videos. Actually I draw the main pipe with the helical tube. I attempted to use Boolean with subatract to create the helical ribs on the outer diameter of the pipe but the process failed and an error appeared as the attached picture? I think the reason is from the helical pipe which looks longer than the pipe extents as shown in the pictures? I am sure that I give the line of the sweep same as that of the pipe length as 1 m? why it appears longer when created? I tried other pitches the same thing happen? 

 

[Rob]

And the search tool on here is quite good too.   

https://forum.ansys.com/forums/topic/simulation-of-bubble-dynamics/?order=all#comment-948a6e0a-933b-4b39-9b53-a92800b6dca9

[mariamsar]

And the search tool on here is quite good too.   

https://forum.ansys.com/forums/topic/simulation-of-bubble-dynamics/?order=all#comment-948a6e0a-933b-4b39-9b53-a92800b6dca9

 

Many thanks but this post in spaceclaim not designmodeler

[peteroznewman]

The advice to avoid tangent conditions and applies to any solid modeling software. Make the helix diameter slightly larger to break though the wall or slightly smaller to leave a small wall thickness. Avoid having two surfaces that are trying to create a zero thickness section.

[mariamsar]

The advice to avoid tangent conditions and applies to any solid modeling software. Make the helix diameter slightly larger to break though the wall or slightly smaller to leave a small wall thickness. Avoid having two surfaces that are trying to create a zero thickness section.

 

I think I will make it slightly larger because if it is smaller then it become useless and helical ribs never added to the outer pipe diameter? I am willing to let the helical ribs added as shown below :

 

[mariamsar]

The advice to avoid tangent conditions and applies to any solid modeling software. Make the helix diameter slightly larger to break though the wall or slightly smaller to leave a small wall thickness. Avoid having two surfaces that are trying to create a zero thickness section.

The advice to avoid tangent conditions and applies to any solid modeling software. Make the helix diameter slightly larger to break though the wall or slightly smaller to leave a small wall thickness. Avoid having two surfaces that are trying to create a zero thickness section.

 

I did the sustract I did successfully but the geomtery looks incorrect because the helical pipe became as grooves see below pict 

 

 

while I want it appears as below pict

 

How I can resolve this problem? any advice please?

Mariam

[peteroznewman]

Mariam, you did not draw the cross-section of the spiral with the 45 degree edges and the correct settings for the sweep.  Import the attached DesignModeler file for an example.

[mariamsar]

Dear Mr. Peter Many thanks for the file. Actually I have some questions about the plot hope you answer me it:

1) As I understood from your plot : I need to draw profile for the sweep as a parallelogram with dimensions and angle of the cross section for the helical rib?

2) why there is a distance left without sweep as shown on the pict below? please look from bottom of the pipe

2) why the path of the sweep not start from the pipe beginning? as I see you started it prior pipe beginning as pict

[peteroznewman]

1) Yes, you need a parallelogram to extrude a spiral tool to cut away material from the pipe. The spiral tool begins above the pipe, is a larger diameter than the pipe and continues past the end of the pipe.

Once the Boolean subtracts the spiral tool from the pipe, a sharp point is created.

2) By adding an uncut piece of pipe at the end, the spike is no longer a spike.

[mariamsar]

 

Thanks for the valuable illustration. Actually I failed to got the sharp point illustrated in step 1 with unknown reason. In addition, may you tell me how I can  add uncut piece of the pipe at the end? I uploaded to you the designModeler file I will be gratiful if you modify it and resend me here.

 

 

[peteroznewman]

I subtracted the helix to create my geometry.

You united the helix to create your geometry.

The result is different geometry.

[mariamsar]

 

1) I followed steps similars to yours exactly except I draw the parallelogram  on the yz-plane instead of xz-plane because I want to make the geometry symmetric along the yz-plane later.

2) I modified the dimensions to make the line of pipe as 1 m hence I exchange the path length to 1005 mm.

3) I used sweap to make the helical pipe along the outer surface then I used Bolean to substract the helix and the geomtery become as below:

4) I extrude the circles at the pipe begining to adding uncut  piece of pipe to remove the spike as below:

3) I attempted to unit the resulted bodies but the problem there is another spike on the other end of the pipe 

I tried to added uncut pipe at this portion of the pipe using extrude (normal) but the body added only at the top of the pipe and I am now unable to remove the spike in this position? any suggestions?

[peteroznewman]

1) I spiral (helix) is not symmetrical about the YZ plane.

Attach your geometry file to your reply and I will look at it.

[mariamsar]

 

Here is my geometry file attached. I draw a body inside the core of the tube which represent the inner fluid. Please try just to remove the spike at the beginning and end of the tube.

Thanks

Mariam

[peteroznewman]

Here you go.

[mariamsar]

Here you go.

Dear Mr. Peter many thanks for your efforts. Actually, there are some steps I did not understand in your drawing and I did it incorrectly I am so grateful if you answer me it and I prefer if you providing with it illustrated screen shoots : 

1) May I know how you create plane 5? as I see you select its type from face but I think I selected the base face for it incorrectly? do you select the inner surface at the inner circle as base face for it?

2) Are there are two circles on sketch 8 or just one?

3) How you create plane 7 and what the base face for it?

Regards

Mariam 

[peteroznewman]

Dear Mariam,

An easy way to understand how a solid model was built in DesignModeler is to use the Suppress & All Below, then Unsuppress one feature at at time. That way, you can more easily see the faces that are selected along the way.

1) Plane 5 used this face.

The slice operation separated the extra helix, which was suppressed, that left a spike.

2) Sketch 8 has two circles.

After an Extrude and Boolean, that end is complete.

3) Plane 7 was built from the face at the +Z end of the pipe.

If this answers your original question, please select a post above that best answered it and make that with Is Solution to mark the discussion Solved, or ask a followup question. If you have new questions, start a New Discussion.

Good luck with the next stage of your model.

Kind regards,
Peter

 

[mariamsar]

Many thanks for the valuable illustrations. After a hard work I succeeded with creating the geometry. There is a thing I have doubt about, i.e. I found in your plot that the inner fluid is not start with the beginning of the helix that we added as below:

 

So that I extrude the first face of the inner cylinder to create a new body with distance 4 mm then I use Boolean to unite it with the inner cylinder as below? is that correct:

In addition, as it clearly appeared from the above picture the geometry not fit to the xy-plane and there is 1 mm distance between it and the xy-plane as seen? I am afraid with that FLUENT not make the domain extents start from 0? 

[peteroznewman]

Yes, add that missing 4 mm as you described.

I don't think FLUENT cares about that 1 mm gap, but if you are concerned, you can make my extrusion 5 mm and the same with your new extrusion.

If your questions are answered for this discussion, please mark the post that best answered your question with Is Solution. That will mark the discussion solved.  Ask new questions in a New Discussion.

Good luck,
Peter

[mariamsar]

OK  many thanks for the answer. Honestly, I still have question to the next step. Now I am aiming to surround this pipe with the outer pipe to form the final geometry of the heat exchanger. The outer pipe has diameter 16 mm with thickness 4. I draw two circles and extruded them and I did several Boolean operations and I suppress some bodies. I sent the geometry file here may you check it? I will be grateful for that. 

Mariam

 

 

[peteroznewman]

Dear Mariam,

I checked it out and it's all correct.  

Kind regards,
Peter

[mariamsar]

Dear Peter,

Many thanks. I tried now to make the geometry symmetric along the yz-plane using the symmetric option but I failed and an error appeared as below 

 

 

May I know what the problem?

Regards,

Mariam

 

[peteroznewman]

Dear Mariam,

A helix does not have symmetry, as I mentioned above.

In the image on the left, I cut a helix in half on the YZ plane.
In the image on the right, I put a mirror image across the YZ plane. They are different, right?

    

Kind regards,
Peter

[mariamsar]

Dear Peter,

Yes, they not the same? Hence I need to use full pipe only?

 

Mariam

[peteroznewman]

Dear Mariam,

Yes, you need to use a full pipe for the most accurate simulation.

You could get an approximate result by drawing rings around the pipe instead of a helix. That can be turned into a 2D axisymmetric model.

 

Kind regards,
Peter

[mariamsar]

Dear Peter,

Many thanks for your efforts. If I am willing to draw rings I need to draw each ring individually?I think it's hard to draw 250 rings of 4 mm apart along a pipe of 1 m long ? 

Mariam

 

[peteroznewman]

You use a Pattern feature in DM.

[mariamsar]

You use a Pattern feature in DM.

I decided to use the full pipe because its reflects better imagnation to the real pipe. May you please added a suitable mesh for it with max skewness not exceeded 0.75 and send me the mesh file here I am highly appreciate that.

Mariam

[peteroznewman]

Good choice Mariam.

I see this Discussion is now so long that I have to click the Show More Posts button to get to the end.

Since your last request is on a different topic, please create a New Discussion. Don't forget to mark this discussion as Solved.

Kind Regards,
Peter