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3D Fluid Structure Interaction Problem Will Not Converge
Posted Jun 2, 2010, 3:07 p.m. EDT Version 5.2 3 Replies
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I would like to model a thin iron cantilever beam bending due to constant water flow normal to the beam. I am having trouble getting the solution to converge for high aspect ratio beams such as the one in the attached file. If I take the aspect ratio significantly lower (less than 5 or 10), then the solution converges; however, I would like to have a solution for a high aspect ratio wire.
Did anyone else run into problems with fluid-structure interaction high aspect ratio models?
Thanks!
Did anyone else run into problems with fluid-structure interaction high aspect ratio models?
Thanks!
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3 Replies Last Post Jun 3, 2010, 4:32 a.m. EDT
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Posted:
1 decade ago
Any inverted mesh problem due to higher deflection? otherwise I can't think of why a longer beam would cause problem and not a shorter one (except numerical errors, ...).
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Posted:
1 decade ago
I do occasionally get inverted mesh problems when I draw similar models, but for this particular model, I do not get inverted mesh problems.
I believe the length of the beam in this model is 50 mm and it does not converge; however, when I run the same exact model with a 5 mm length, it does converge.
I believe the length of the beam in this model is 50 mm and it does not converge; however, when I run the same exact model with a 5 mm length, it does converge.
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Posted:
1 decade ago
Hi
I'm no fluidics expert, but I would say start in 2D its faster to debug.
When I try fluidics I often run into convergence problems, like you.
One thing I'm always fighting with is the gauge pressure and absolute pressure, for me, in my mind, p=0 means rho=0 hence no mass to act on the structure, but this is not so in fluidics.
Nevertheless, and I do not know really why, when I use p0=1 for initial pressure (and outlet pressure) my models goes further, or converges better, for some time, (your model too) but often like here never ends. In fact the slightest mesh change also changes the convergence, so we are missing some physics "knob" to turn correctly here.
I hope that the CFD module will be better tailored, but fluidics has always been a special domain for it gurus ;)
Have fun Comsoling
Ivar
I'm no fluidics expert, but I would say start in 2D its faster to debug.
When I try fluidics I often run into convergence problems, like you.
One thing I'm always fighting with is the gauge pressure and absolute pressure, for me, in my mind, p=0 means rho=0 hence no mass to act on the structure, but this is not so in fluidics.
Nevertheless, and I do not know really why, when I use p0=1 for initial pressure (and outlet pressure) my models goes further, or converges better, for some time, (your model too) but often like here never ends. In fact the slightest mesh change also changes the convergence, so we are missing some physics "knob" to turn correctly here.
I hope that the CFD module will be better tailored, but fluidics has always been a special domain for it gurus ;)
Have fun Comsoling
Ivar