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Basic COMSOL question

  1. Oct 9, 2007 #1
    Hi, Im pretty newish to comsol.
    Im having a simple problem in constructing my geometry
    How exactly can you draw lines from one point to another when you dont know the coordinates of the points?
    My geometry is pretty complicated and its difficult to find the coordinates of the points. So is there like a way I can select the 2 points on the geometry to draw a line.
    Or is there a way to find out the exact coordinates my my points.
    Thanks alot
     
  2. jcsd
  3. Oct 9, 2007 #2

    PerennialII

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    You can certainly define lines simply by "drawing them" without specifying the points as separate entities explicitly, but you're still forced to take a stand on their location (in the grid for example). If the geometry is complicated, it may be appropriate to try to model it using other primitives likes circles, ellipses, splines etc. and then cut, merge, edit sections and so on (like to avoid having to calculate specific auxiliary points which don't really "exist" in your geometry). Comsol isn't (yet) really strong in creating geometry and that's why the solidworks link is pretty strong what comes to model generation (so depending on what modules and so forth you've included in your install of comsol doing the geometry with a more appropriate software package might be an option as well).
     
  4. Oct 9, 2007 #3
    so how exactly do you just "draw" these lines? I always see the option to enter coordinates
     
  5. Oct 10, 2007 #4

    PerennialII

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    ....when you're in "draw mode", pick the line tool (or the bezier tool) and then you can draw lines on the workbench.
     
  6. Oct 10, 2007 #5
    hmm..yeah i know you just click the "line" tool. But when i click that I have to enter coordinates to specify my line.
    I was looking for a way to just draw a line on the workbench itself by just clicking anywhere and moving the mouse...like how some CAD programs are.
     
  7. Oct 10, 2007 #6
    oh i figured out whats going on, you can only draw lines like that in 2D..I was working in 3D all the time. But I guess Comsol doesnt allow you to do that in 3D just yet, huh?
    Thanks for the help!
     
  8. Oct 10, 2007 #7

    PerennialII

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    yeah I didn't figure out you were in 3D .... yeah, lots of the 3D work is done on 2D surfaces of the 3D objects and then have to specify how to generate the object from the planar surface. And as you've probably noticed it's not like a "real CAD" software in terms of generating a model and anything beyond relatively simple troublesome fast. Being able to edit the sections and then reassemble them works pretty good though.
     
  9. Mar 20, 2008 #8
    Hello.
    Does anybody know how to implement periodic boundary conditions in 1D model without usage of GUI? Old fem.equiv is removed and something like this (found in mph file) doesn't work:
    pair{1}.type= 'identity';
    pair{1}.name= 'Pair 1';
    pair{1}.src.dl = 1;
    pair{1}.dst.dl = 4;
    bnd.pair = pair;
    fem.bnd = bnd;
    Let say I want to use periodic at the 1 and 4 boundaries. How can I do it?
    Thank you.
     
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