- Is there any particular reason why you use
<relative-convergence-measure limit="1e-4" data="Displacements" mesh="Structure_Nodes"/>
<relative-convergence-measure limit="1e-2" data="Forces" mesh="Structure_Nodes"/>
No really, but if I use more strict precision for the forces, the simulation takes a lot of time and the results are not better.
On the other hand, the parallel coupling is less stable than Serial coupling for this case. I was using IQN-ILS with “0” time-windows-reused and 25 max-used-iterations, making the simulation more stable but not enough to finish the required time (0.85). See the video
https://drive.google.com/file/d/1GUvul8tab72HvaYIqBgiMpLdvkIIXzlR/view?usp=sharing
The conflict starts when the beam should return and begins to oscillate.
Concerning the IQN-IMVJ acceleration, I tested it but this appears less effective than IQN-ILS.
For this point with the acceleration methods. How can decide correctly the value for the filter, the number of reused iterations, and time reused?
I think this test case is very tricky if I change something in the coupling configuration I have the following problems:
- If the time is bigger, Calculix converges very fast and the simulation is more stable but Fastest diverges because the multiphase model does not support very large time-steps.
- If the time is smaller and appropriate for the multiphase fluid, Calulix diverges after a few coupling interactions.
- If the grids are coarse in the two programs, I can simulate the test case but the results are not enough accuracy. Therefore, I am trying to simulate the case using finer grids. How can be a good proportion between the fluid and structure elements at the fluid-structure interface?
- This test case is a 2D case (0.8mx0.8m fluid domain, 0.004mx0.09m rubber beam), I only have one volume on the z-axis (for FASTEST) and in the mapping setup z-dead=true. However, I do not know what is the appropriate width for the grid in the z-direction. On the one hand, if I use a very small value, for example, 0.002 or 0.006, the grid aspect ratio for the fluid domain is okay, but the RBF mapping diverges and to works requires at less 2 elements (C3D20R or C3D8i) are defined in the z-direction of the structure. On the other hand, if the width value is greater e.g. 0.2m, the RBF mapping works only with one element in the z-direction of the structure, but I notice in the vtk-files that the displacement is different for the parallel points, which is not logical if the case is 2D. My question is how can I decide the appropriate width for a quasi2D case? and how can I avoid these unequal displacements? To clarify my question, I attach the force and displacement values for 2 parallel points. The forces received are equal and the displacement unequal results in a complicate deformation of the fluid grid.
- Finally, in this case, the structure is a rubber beam (E=3.5MPa, nu=0.5), I am still using the elastic model (with nu=0.49) and the non-linear effects are considered (NLGEOM). Do you think that it is adequate? or the hyperelastic model should be used? However, for the hyperelastic model, I do not have the complete parameters that require these models. Maybe do you have more information about the constants for a rubber material?