Discussion Forum

Hi

if I remeber right (I do not have access to COMSOL just now) you need to define the centre for the scaling, so if ech sphere is at different position, you need to define N times your scaling function. But you can define a parameter and use that to control all in "one go" (at least in v4, not sure it works OK in 3.5, you must try).

But what sends up a warning sign to me is you are mentioning the sphere will overlap, that forme means a topology change, hence new domains and boundaries, but COSMOL (or any other FEM tool) CANNOT decide for you have the BC (boundary conditions) should propagate when such topology changes occure, furthermore the Entity (domain, boundary, edge point) "id's" will change, and the wrong BC will end up on a wrong place

You must split your analysis and redefine it manually when you change the topolog of your geoemtry

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Good luck
Ivar

i think i got your point..but unfortunately this is not what i want..as you are saying in that way all the balls will expand but will not overlap...but i want them to overlap after the expansion...because what you are saying i have done that and the balls are not overlapping after expansion they are just expanding as a whole bunch and i need them to stay there and they should expand there outer boundaries and then they should be overlapped by one another after expansion (just like fingers of my both hand can overlap in to one another) ...if you understand me then please do it for me ....and then tell me how you do this step by step....well i am a new user of comsol so i want you to tell me step by step( like first click this button then this and so on...)...thank you

Hi

I'm not sure I really catch your model, for me you say the spheres overlap, but what do you reaqlly mean by that ? you have some material inside your domain =surfaces or volumes, depending if you are in 2D or 3D respectively. But if they overlap ? whci material appear in each domain ?

Try the exercices of the CAD building, see the examples in the doc, then I'm sure you will quicly learn how to generate even complex geometries

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Good luck
Ivar

OK i will try to tell you in a simple way ..... for example i have made 1st sphere (radius 2m) in 3D(at axis--> x=1,y=1,z=1) from the geometry tools .. OK.....now i have made a 2nd sphere (radius 2m) in 3D (at axis --> x=4, y=1,z=1) again from the geometry tools....now you can imagine that they will appear like two tennis balls standing side by side and touching there outer boundary with each other.....now i want to expand them and there radius should be for example(2.5m).....and when i will expand them they should overlap each other from the same side from where they were touching each other....like two tennis balls are merged slightly in to one another.....right now i wanna tell you how i am expanding them....i am expanding them one by one by changing there radius from the object properties option and not changing there X , Y and Z axis position......and this way they are expanding and getting slightly overlapped but this way is very difficult for the 100 or more spheres so i want from you to tell me some way to expand there radius together not one by one....now i want to clear you that.....i am just making a geometry nothing else ......i am not applying any boundry conditions...or any equations......it is just startup of making geometry.....i am just make a geometry.......now i think you will understand my problem......what you have told me before about the scaling factor.......when i will increase the scaling factor but by this way they are expending there radius but not slightly overlapping......i am showing you one symbol which i have copied from Microsoft word and pasted here.. my two slightly overlapped spheres will look upto some extent like this symbol ( ? ) or may be like this ( ? ) .

Thank you so much

Hi

you do not want them to penetrate, so the confusion is then that what you call "overlap" is for me a "contact" boundary, where the boundary deformes but the two spheres do not penetrate one inside the other.

In this case for me the only limitation is that you should work in assembly mode, and define contact pairs boundaries. There are different exercices and example on this in the doc and the model library

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Good luck
Ivar