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Note: This discussion is about an older version of the COMSOL Multiphysics® software. The information provided may be out of date.

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about helix geometry modeling

Posted 2013年2月18日 GMT-5 23:37 Geometry, Studies & Solvers Version 4.3a 12 Replies

Shijie Chen
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Hi, I am trying to model a spiraling geometry (helix-like) with a complicated cross section. Does anyone know how to do it with comsol 4.2/4.3a?

I used the build-in "helix" one but that was with a circle cross section while what I want is actally not that simple.

Thanks for any feedback!
12 Replies Last Post 2013年7月8日 GMT-4 09:21
Sergei Yushanov Certified Consultant
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Posted: 1 decade ago 2013年2月19日 GMT-5 09:00
Shijie,

Use Parametric Curve and Sweep options to create helix of arbitrary cross-section. Example is shown in the attached file.

Regards,
Sergei
Shijie, Use Parametric Curve and Sweep options to create helix of arbitrary cross-section. Example is shown in the attached file. Regards, Sergei

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Shijie Chen
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Posted: 1 decade ago 2013年2月21日 GMT-5 01:36
Thanks for your help. It works.

But now just comes up with another two questions:

~what's happening at the apex? ( the parametric curve is actually not smooth which causes the built geometry not smooth as well)

~If I wanna have some equal separated points in along the parametric curve (equal distance from the curve i.e. now it's point instead of plane and the 1st point has been built). I cannot not use "sweep" here cuz those points I want are not continuous.

Cheers

Thanks for your help. It works. But now just comes up with another two questions: ~what's happening at the apex? ( the parametric curve is actually not smooth which causes the built geometry not smooth as well) ~If I wanna have some equal separated points in along the parametric curve (equal distance from the curve i.e. now it's point instead of plane and the 1st point has been built). I cannot not use "sweep" here cuz those points I want are not continuous. Cheers

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Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 2013年2月21日 GMT-5 01:51
Hi

you might need to adapt the twist angle ;) and for defining the number or distribution type of points along the sweep direction you have the "dimension" sub tab on the mesh node to play with. Check the doc, there are many subtleties in the meshing part

--
Good luck
Ivar
Hi you might need to adapt the twist angle ;) and for defining the number or distribution type of points along the sweep direction you have the "dimension" sub tab on the mesh node to play with. Check the doc, there are many subtleties in the meshing part -- Good luck Ivar
Shijie Chen
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Posted: 1 decade ago 2013年2月21日 GMT-5 23:43
Thanks Ivar

But I didn't see "dimension" sub tab on the mesh node(see attachment)... Or is it possible to use a for-loop directly in comsol?

If I wanna decrease the cross section along sweep direction, should I use "motion of cross section"? and how do I set scale factor? (I set parameter name as 's' and any scale factor with s will give me an error "cannot find a valid topology for the generated geometry object"/"internal geometry error")

Cheers
Thanks Ivar But I didn't see "dimension" sub tab on the mesh node(see attachment)... Or is it possible to use a for-loop directly in comsol? If I wanna decrease the cross section along sweep direction, should I use "motion of cross section"? and how do I set scale factor? (I set parameter name as 's' and any scale factor with s will give me an error "cannot find a valid topology for the generated geometry object"/"internal geometry error") Cheers

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Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 2013年2月22日 GMT-5 01:45
Hi

sorry my fault it's "Distribution",

read the doc about the mesh nodes, its important to understand in which order you call them and the difference of a major node and a sub node, performing a few of the model library examples helps too, at least those (or the video) about the meshing

--
Good luck
Ivar
Hi sorry my fault it's "Distribution", read the doc about the mesh nodes, its important to understand in which order you call them and the difference of a major node and a sub node, performing a few of the model library examples helps too, at least those (or the video) about the meshing -- Good luck Ivar
Shijie Chen
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Posted: 1 decade ago 2013年2月28日 GMT-5 00:05
Hi Ivar

There are two parts that I need help in my model attached.

~ How to taper the cross section along the parametric curve to avoid overlap of material (in current model I increase the radius and height to avoid it which is non-realistic), supposing I know the tapering function

~Is it possible to extrude the workplane in the direction of the curve without any twist. i.e. the corss section is always perpendicular to the base plane(xy-plane). just like the attached image, I think it might be achievable. Otherwise, since I don't know the function of twist. It would be impossible to track the path of a specific point of the workplane which is actually very important for me.

It'd be very nice of you if you can offer some solution/idea. Thank you very much.
Hi Ivar There are two parts that I need help in my model attached. ~ How to taper the cross section along the parametric curve to avoid overlap of material (in current model I increase the radius and height to avoid it which is non-realistic), supposing I know the tapering function ~Is it possible to extrude the workplane in the direction of the curve without any twist. i.e. the corss section is always perpendicular to the base plane(xy-plane). just like the attached image, I think it might be achievable. Otherwise, since I don't know the function of twist. It would be impossible to track the path of a specific point of the workplane which is actually very important for me. It'd be very nice of you if you can offer some solution/idea. Thank you very much.

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Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 2013年2月28日 GMT-5 01:24
Hi

I'm not sure about tapering in COMSOL, the twist is an issue too, I haven't really managed to get it right, sometimes I wonder how much is a graphical issue and how much is real ;)

I would too be interested to see how to get the shape right. There are several threads over the last years about this, worth a search on the Forum

--
Good luck
Ivar
Hi I'm not sure about tapering in COMSOL, the twist is an issue too, I haven't really managed to get it right, sometimes I wonder how much is a graphical issue and how much is real ;) I would too be interested to see how to get the shape right. There are several threads over the last years about this, worth a search on the Forum -- Good luck Ivar
Atilla Savas
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Posted: 1 decade ago 2013年3月17日 GMT-4 05:00
Hi,

How can I draw a solid helix in Comsol 3.5a?

İs there a simple way to do this?

thanx in advance.

atilla
Hi, How can I draw a solid helix in Comsol 3.5a? İs there a simple way to do this? thanx in advance. atilla
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 2013年3月17日 GMT-4 11:12
Hi

I'ma fraid that was brought in in v4, but check carefully the Forum, it has been discussed previously I believe

--
Good luck
Ivar
Hi I'ma fraid that was brought in in v4, but check carefully the Forum, it has been discussed previously I believe -- Good luck Ivar
Leigh Stanger
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Posted: 1 decade ago 2013年6月28日 GMT-4 11:59
Hi

I manged to get a tapered helix by putting 1+f(s) (where f(s) is the function of s required) in the scale factor box.
Im not sure what the scale or bounds of 's' are or where you would find these
Hi I manged to get a tapered helix by putting 1+f(s) (where f(s) is the function of s required) in the scale factor box. Im not sure what the scale or bounds of 's' are or where you would find these

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Shijie Chen
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Posted: 1 decade ago 2013年7月2日 GMT-4 23:12
Hi Leigh:

Thanks for your information. I'd like to see how it goes. Unfortunately I couldn't open the attachment cuz I am using COMSOL 4.3a and it just gave an error "Model created with a later version of Comsol". Can you please fix it or can you just send me some snapshot about the settings. Thanks in advance.

JC
Hi Leigh: Thanks for your information. I'd like to see how it goes. Unfortunately I couldn't open the attachment cuz I am using COMSOL 4.3a and it just gave an error "Model created with a later version of Comsol". Can you please fix it or can you just send me some snapshot about the settings. Thanks in advance. JC
Leigh Stanger
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Posted: 1 decade ago 2013年7月8日 GMT-4 09:21
Hi JC

I dont know how to save as a previous version so here is a screen shot the important bit seems to be the 1 in the scale factor box.
I would still like to know what the bounds on the parameter s are.

Leigh
Hi JC I dont know how to save as a previous version so here is a screen shot the important bit seems to be the 1 in the scale factor box. I would still like to know what the bounds on the parameter s are. Leigh

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