How to create restart files

[stoykov]

Hello again,

I am back to the problem with continuation from previous solution. Still I cannot obtain the same solution if I restart from some time step (the difference is small, but there should be no difference). For example, if I find the solutions for time steps from 0 to 10, then if I restart from time step 5, the solutions at time step 6 and the rest are different.

I am solving elasticity problem, thus the equation is of second order. It it written in the ElmerSolver Manual that for second order equation, Time Derivative Order must be set to 2 and that it is always discretized using Bossak method.

If you look in this method, to obtain the solution at time t_n+1, it uses the solution, velocity and the acceleration at time t_n, see eq. (5.7) from ElmerSolver Manual.

Thus, I think that we need to save not only the dispalcement and the velocity, but also the acceleration, in order to continue from previous solution. I did not find anything like Calculate Acceleration = Logical True and probably it uses zero vector for the acceleration. On the other hand, the acceleration at time t_n+1 can be calculated, once the displacement vector and the velocity are known at time t_n+1.

Can someone comment, or give an idea how to continue from previous solution?

Cheers,
Stan

[rimple_sandhu]

Any luck? I am facing the same issue. I think we need a way to communicate the acceleration info from previous time-step to resolve the issue?

Stan, were u able get hold of the issue?

Regards,
Rimple

[raback]

Hi

There is now an imperfect remedy in:
viewtopic.php?f=3&t=2808&sid=0752143b7a ... 613#p15551

-Peter