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modifying Vibrating Beam in Fluid Flow
Posted 2013年4月4日 GMT-4 09:59 4 Replies
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I am trying to modify Vibrating Beam in Fluid Flow, which is given a example of FSI on this site.
what I want to change is the condition of the cylinder.
In this example, the cylinder is fixed, however, i want to know about the effect of rolling cylinder when the cylinder could rotate freely on the certain location. So, I tried to change the restrained conditions of the cylinder to rotate on a certain location without moving to x or y axis. However, i could not find out the method to fix the rotating cylinder .
In this case, how do i restrain the movement of the cylinder. Do i couple other physics?
what I want to change is the condition of the cylinder.
In this example, the cylinder is fixed, however, i want to know about the effect of rolling cylinder when the cylinder could rotate freely on the certain location. So, I tried to change the restrained conditions of the cylinder to rotate on a certain location without moving to x or y axis. However, i could not find out the method to fix the rotating cylinder .
In this case, how do i restrain the movement of the cylinder. Do i couple other physics?
4 Replies Last Post 2016年9月23日 GMT-4 05:46
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Posted:
1 decade ago
Hi
if the axis of your cylinder is fixed, then rotating the cylinder with noslip, or rotating with "moving wall" via equations is "just" a reference change, so if you rotate the BC at the true cylinder rotation speed, you should be up to the same, no ?
--
Good luck
Ivar
if the axis of your cylinder is fixed, then rotating the cylinder with noslip, or rotating with "moving wall" via equations is "just" a reference change, so if you rotate the BC at the true cylinder rotation speed, you should be up to the same, no ?
--
Good luck
Ivar
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Posted:
10 years ago
Dear Dr Ivar,
I put my question regarding FSI convergence problem on COMSOL forum a few days ago. However I haven't received any answer for it yet. I was wondering if you could give me some advice on how I can sort out the convergence issue. My question is:
There is an example of Fluid-Structure interaction problem given in Comsol model library which is an oscillating beam. I tried to give some change to that model. I separated the beam from the cylinder to investigate the detached splitter plate, removed the Gaussian pulse function and the point load, and applied a fixed displacement constraint to the plate's edge opposite the cylinder. The solution diverged. even when I assumed that the plate is rigid; the solution did diverge . If I run this simulation for an splitter plate attached to the cylinder without point load and Gaussian pulse function, the solution is convergent. Can anyone suggest why my simulation is not convergent in the other two cases?
Many thanks,
Bryan
I put my question regarding FSI convergence problem on COMSOL forum a few days ago. However I haven't received any answer for it yet. I was wondering if you could give me some advice on how I can sort out the convergence issue. My question is:
There is an example of Fluid-Structure interaction problem given in Comsol model library which is an oscillating beam. I tried to give some change to that model. I separated the beam from the cylinder to investigate the detached splitter plate, removed the Gaussian pulse function and the point load, and applied a fixed displacement constraint to the plate's edge opposite the cylinder. The solution diverged. even when I assumed that the plate is rigid; the solution did diverge . If I run this simulation for an splitter plate attached to the cylinder without point load and Gaussian pulse function, the solution is convergent. Can anyone suggest why my simulation is not convergent in the other two cases?
Many thanks,
Bryan
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Posted:
10 years ago
Hi
there is probably no "one answer" but I would suspect that if you use a discrete stepwise boundary condition you will get convergence issues as normally to find a steep slope solution the functions should be continuous if not at least derivable once, preferably twice. This should remind you something from the time of your analysis courses no ?
And you talk about "point loads", normally one should avoid them. When possible any loading on Entities such as points in 2D or 3D (and even on edges in 3D) are to be avoided. Keep the loadings to the Boundaries of your domain dimension, because else you create mathematical singularities that makes solver convergence difficult if not simple impossible
Basically, be sure you BC's are "physicals", nothing turns on instantaneously I real life, even a front to front collision starts smoothly, even if the gradient rapidly gets rather steep ;)
--
Good luck
Ivar
there is probably no "one answer" but I would suspect that if you use a discrete stepwise boundary condition you will get convergence issues as normally to find a steep slope solution the functions should be continuous if not at least derivable once, preferably twice. This should remind you something from the time of your analysis courses no ?
And you talk about "point loads", normally one should avoid them. When possible any loading on Entities such as points in 2D or 3D (and even on edges in 3D) are to be avoided. Keep the loadings to the Boundaries of your domain dimension, because else you create mathematical singularities that makes solver convergence difficult if not simple impossible
Basically, be sure you BC's are "physicals", nothing turns on instantaneously I real life, even a front to front collision starts smoothly, even if the gradient rapidly gets rather steep ;)
--
Good luck
Ivar
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Posted:
8 years ago
Hi,
Seungyon,
Have you find the method to rotate the cylinder in this example model?
I have the same trouble with you.
Please let me know if you have some suggestions.
Best regards,
Humlyon
Seungyon,
Have you find the method to rotate the cylinder in this example model?
I have the same trouble with you.
Please let me know if you have some suggestions.
Best regards,
Humlyon