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How to construct a Hexa-/Octa-gon 3D "cone" in comsol

Posted 25 nov 2019, 05:05 GMT-5 Geometry, Modeling Tools & Definitions Version 5.4 4 Replies

Tamer Tolba
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Dear all,

For my heat transfer in soild model, I am trying to study the thermomechanical behavior, e.g. bulk temperature distribution and structure deformation, of some solid structure due to heat deposits on its surafce. So far, I have no problem studying regural 3D design structures, e.g. a block, a cylinder, a cylindrical cone, etc. But I am not able find a way to darw a Hexa-/Octa-gon "cone" structure, where the top "radius" != bottom "radius". I can extrude a 2D hexa-/octa-gon, but this will result in a piller like structure, i.e. top "radius" = bottom "radius".

Any good idea?

Regards, Tamer

4 Replies Last Post 28 nov 2019, 12:42 GMT-5
Magnus Ringh COMSOL Employee

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Posted: 5 years ago 25 nov 2019, 07:45 GMT-5

Hi Tamer,

You should be able to use the scale factors under Scales (equal scales, smaller than 1, in the xw and yw directions) in the Settings window for Extrude to make the resulting 3D geometry into a cone-like shape.

Best regards,

Magnus Ringh, COMSOL

Hi Tamer, You should be able to use the scale factors under **Scales** (equal scales, smaller than 1, in the xw and yw directions) in the **Settings** window for **Extrude** to make the resulting 3D geometry into a cone-like shape. Best regards, Magnus Ringh, COMSOL
Tamer Tolba
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Posted: 5 years ago 28 nov 2019, 05:40 GMT-5

Hi Magnus,

Thanks for you prompt reply, and my apology for the delay in replying (it seems that I deactivated the notification via email, so actually I was waiting the whole time to get some reply!) Anyways, I tried you suggestion (Extrude -> scale). Actually, it is very strange feature! It seems that it fixes one "side-plane" of the 4pi of the extruded structure, then it scale the other faces! So what you get as a result is a titled-shrinked, uneven distributed scalling, structure. What I expect is to fix the center of the 2D plane and use it as a scaling reference, so the shrink/scale in equal in all 4pi Please check the attached model and you will get what I mean. Now, If you disabled the HoneyCell structure and enabled the rest, you will see what I need at the end, but change the normal cone to a honeycell cone structure!

Hi Magnus, Thanks for you prompt reply, and my apology for the delay in replying (it seems that I deactivated the notification via email, so actually I was waiting the whole time to get some reply!) Anyways, I tried you suggestion (Extrude -> scale). Actually, it is very strange feature! It seems that it fixes one "side-plane" of the 4pi of the extruded structure, then it scale the other faces! So what you get as a result is a titled-shrinked, uneven distributed scalling, structure. What I expect is to fix the center of the 2D plane and use it as a scaling reference, so the shrink/scale in equal in all 4pi Please check the attached model and you will get what I mean. Now, If you disabled the HoneyCell structure and enabled the rest, you will see what I need at the end, but change the normal cone to a honeycell cone structure!
Edgar J. Kaiser Certified Consultant
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Posted: 5 years ago 28 nov 2019, 12:10 GMT-5

Hi Tamer,

since the center of the polygon is not at (0, 0) you need to use a displacement as well. Using xw = 0.5 and yw = 0.5 fixes it, I think.

Cheers Edgar

-------------------
Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com
Hi Tamer, since the center of the polygon is not at (0, 0) you need to use a displacement as well. Using xw = 0.5 and yw = 0.5 fixes it, I think. Cheers Edgar
Tamer Tolba
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Posted: 5 years ago 28 nov 2019, 12:42 GMT-5

Hi Edgar,

Thanks so much. I solved it with modifying the displacment feature!

However, and just for completness, it is not really just putting the dispalcment variables, xw and yw, at the cenetr of the polygon (which is in my case x=0.5, y=0.5). There is kind of relation between the the displacment values, the center of the polygon (that gonna be extruded) and the scaling factor!

Imperically I found the displacment values, like this: xw = x_center_polygone (value of the cenetr of the polygon in x direction) - scaling_Factor/2 yw = y_center_polygone (value of the cenetr of the polygon in y direction) - scaling_Factor/2

So, if, in the model that I sent you, you put xw=0.5 and yw=0.5 (putting in mind the the center of the polygon is at x=0.5 and y=0.5), and "build", this will still result in an unevent structure! But if you put xw=0.5-(0.4/2) and yw=0.5-(0.4/2) (where 0.4 is the scalling factor), this will result in correct structure.

Many thanks to you and Magnus!

Best regards, Tamer

Hi Edgar, Thanks so much. I solved it with modifying the displacment feature! However, and just for completness, it is not really just putting the dispalcment variables, xw and yw, at the cenetr of the polygon (which is in my case x=0.5, y=0.5). There is kind of relation between the the displacment values, the center of the polygon (that gonna be extruded) and the scaling factor! Imperically I found the displacment values, like this: xw = x_center_polygone (value of the cenetr of the polygon in x direction) - scaling_Factor/2 yw = y_center_polygone (value of the cenetr of the polygon in y direction) - scaling_Factor/2 So, if, in the model that I sent you, you put xw=0.5 and yw=0.5 (putting in mind the the center of the polygon is at x=0.5 and y=0.5), and "build", this will still result in an unevent structure! But if you put xw=0.5-(0.4/2) and yw=0.5-(0.4/2) (where 0.4 is the scalling factor), this will result in correct structure. Many thanks to you and Magnus! Best regards, Tamer

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