Vertical 2D axisymmetrical modeling is the default in COMSOL Multiphysics. Whether horizontal 2D axisymmetrical modeling is possible? Please explain the same?
Dear Faisal
When i searched just now in comsol forums - I come to know that it is not possible to simulate horizontal 2D axisymmetric problems using 2D axisymmetric option. Instead we have to use 3D modeling.
http://www.comsol.co.in/community/forums/general/thread/41999/
http://www.comsol.co.in/community/forums/general/thread/34156/
http://www.comsol.co.in/community/forums/general/thread/18926/
Where is the problem in doint it vertical? For your model, it does not matter if you turn it by 90 degress to have it vertical. If there is gravitation, you can have a horizontal volume force. If it is just for the nicer look, you can rotate your post-processing.
So why don't you just set it up horizontally? You have to setup the volume force anyway in comsol, just give it a horizontal direction vector.
Dear Nils - That is the limitation in the comsol which can be understood by the forum threads I have shared above - I have tried COMSOL for giving an inclined / horizontal axis, but not able to succeed
I still do not see the problem. Even if you have an inclined axisymmetric geometry in a gravitation field, you can solve the problem with a vertical symmetry axis if you change the direction of the graviation field accordingly. You can do that in the volume force dialog from comsol (see attachment). If this does not help, it would be good if you could upload a simple sketch of what you are trying.
For axisymmetric elements the axis of rotation is generally fixed as either the X or the Y axis. So you will need to transform your loading according to this convention. However if you are considering gravity loading then this is NOT an axisymmetric load form so you will need to consider a three-dimensional model or else look at the features in the software that might allow you to use the axisymmetric model with non-axisymmetric loading. This generally involves approximating the load as a fourier series and then conducting a series of analyses on the different terms - the results are then summed to give you a non-axisymmetric result. I would save yourself the hassle of doing this and go straight to three-dimensions.
As far as I know, COMSOL put its axis of symmetry vertically and I do not know the way to change it. But this is just a convention, a representation. In Fluent, for instance, it is horizontal and you cannot change it, so if you want to simulate a rising bubble, the flow is simply set as horizontal. Therefore, you may simply adapt how you implement your equation system in the COMSOL fields for body forces, conservative fluxes, ... . For instance, if you have gravity perpendicular to the symmetry axis, just set the body force in the x-component instead the y-component.
I hope it helps.
Yes, its straight forward. When COMSOL menu pop-up: follow steps:
New-in the space dimension- click on arrow-then choose- Axial symmetry (2D)-OK
and then start your model. Thats for COMSOL3.5a and I think you can follow the stepds with other version of COMSOL.
As far as I understoof the problem is that if the volume force has a radial component the problem is not axially symmetric anymore.
Thanks a lot Christophe Wylock - You have changed my view of looking the numerical problem - Thanks again
Okay, if the axis of axial symmetry is vertical then a gravity load is axisymmetrical.
That is my understanding of an axisymmetric problem - none of the field variables vary in the circumferential direction. This is why I originally objected to the idea of including gravitational loading in the model. But with a little thought it is okay provided the axis of symmetry is vertical or, alternatively, your gravitational load is along the axis of symmetry.
- Badges
- Science topic
- Similar topics
- Engineering
- Mechanical Engineering