Hi Everyone, I have been using dealii to solve nonlinear elasticity problem like step-44. The problem is geometry nonlinear only without any material nonlinearity. I have implemented two versions of codes to solve it. One is implemented as step-44, namely in a smp way. The other one is implemented as step-17 and step-18, namely in a dmp way. And I am using petsc to solve the linear equations. I found something interesting and I want to share it with you.
1. When I use SI-system (N-m-s), the material properties value will be really large as expected. For example, the Young's modulus will be 1e11 Pa. Somehow, the dmp code will behave very strangely in this case. The CG will finish in 0 iteration and the solution will be empty. If I change the unit system to be N-mm-s, the Young's modulus become 1e5 MPa and then the CG starts to behave normally. The smp code seems to be more insensitive to the type of unit system. 2. Although the finally results of smp and dmp are the same, the computational time is different. Surprisingly, the dmp code is slower than smp code. It is not because the CG is slower in dmp, it is somehow the dmp code will need more N-R iterations them smp. Based on the above observation, I have feeling that there are some loss of accuracy when using petsc. Most likely it happens when we transfer Vector or Matrix between petsc and dealii. I am not sure if any of you has encountered those situations before. I need some advices about how to ensure the accuracy when using petsc in dealii. Thanks. -- The deal.II project is located at http://www.dealii.org/ For mailing list/forum options, see https://groups.google.com/d/forum/dealii?hl=en --- You received this message because you are subscribed to the Google Groups "deal.II User Group" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion visit https://groups.google.com/d/msgid/dealii/49484134-9a34-4c11-88f9-475c0f25165fn%40googlegroups.com.
