Le jeudi 21 décembre 2006 09:15, Emilio Melero García a écrit : > Dear Stephane, Dear Emilio.
> thank you so much for your help and patience. I will certainly increase the > time step. It is a very good solution even with the memory leak since i do > not need to go foward in time so much (no more than 13 days, which are only > 936 iterations with dt=1200). > > By the way, and i understand it is not the place to ask these, and that you > might be very busy to answer, the stability condition that you mention and > the residual of the conjugate gradient is due to the problem i am trying to > solve or is inherent to the PDE solver you have implemented?, and if it is > problem dependent, could you hint me on how did you evaluate the residual > and the stability? First the residual: - it is just written by ff3d when the default verbosity (3) is used. - for your problem, it is always small because your time step so small that the difference between u(n+1) and u(n) is very small... Second concerning the stability: The time scheme you use [u(n+1)-div(dt*grad(u(n+1))) = u(n)] is unconditionally stable. This means that you can choose the time step arbitrarily... > And finally, i am trying to make my way into all this > world of FEM problems and solvers, but i still have a notion that i might > be resorted to implement my own very specific FEM code, any good book you > would recommend to learn FEM methods and implementations? Well there are many good books for finite elements. I recommend the book from Ciarlet for the basis of the theoritical point of view. For the implementation, there are a lot that depend on the physic you want to simulate... Anyway ff3d might be the solution to your problem: can you describe the specificities you are facing? Also, some people have already done it: you can modify ff3d to fit your needs and if that can be useful for others you can then distribute your changes, ff3d is distributed under the GPL... > Please, as i said i understand this might be not the place to ask these > things but i have felt that people in these list read the e-mails and > answer when they can. So please, consider this a question to the people in > the list. No, I think it is a right place to ask this kind of question! Feel free for that. > Thank you very much from a newbie. You are welcome! Best regards, Stephane. PS: sorry for this late answer, due to holidays ;-) _______________________________________________ ff3d-users mailing list [email protected] http://lists.nongnu.org/mailman/listinfo/ff3d-users
