THIS IS AN AUTOMATED MESSAGE, DO NOT REPLY. The following task has a new comment added:
FS#238 - Improve terminology in Newton output / parameters User who did this - Bernd Flemisch (bernd) ---------- Out of a private email from Jos Maas: I looked at your terminology issue on absolute and relative errors. I agree that it is currently confusing and that probably there is no standard terminology. On the other hand, it must be possible to come to a more clearer description of what is being monitored when dealing with the tolerance settings. In my view, the confusion that exists now is 2-dimensional: your "absolute error" is not absolute but relative (normalised) just like your relative error; and secondly, the residuals and the "delta's" are measuring different things. Firstly, I think it is important to keep a clear distinction between the error margins of solving the material balance equations, i.e. the residual of the functions on the one hand, and looking at delta's in the primary variables on the other hand. The delta's are often called "shifts". The residuals drive the NR process and translate immediately into a mass-balance error, either over each cell/box individually or over the whole model. The mass-balance error can be reported as an average, possibly weighted and there are several choices one can make for the weighing. A mass-balance tolerance therefore could be offered to the user, either in absolute terms (kg's) or in relative terms, un-weighted or weighted. A tolerance on shifts is less clear in how that impacts the final results in terms of e.g. production forecast of an oil or gas reservoir. Clearly, a tolerance on shifts may need to take into account scaling: a shift in pressure is something completely different from a shift in saturation (or temperature for thermal runs, assuming the DuMux would use temperature as a primary variable (I never used thermal in DuMux yet)). One could offer a tolerance on relative shifts, or even separate tolerances on separate variables, i.e. a maximum pressure shift, a maximum saturation shift and a maximum temperature shift. Different problems may require different tolerance uses. For your information, in Shell people would focus on mass-balance errors and have less interest in maximum shifts. For my simulations of core analysis experiments, both the errors and the maximum shifts are important, but still I would first require a good tolerance on the mass-balance (1.E-14 or smaller, for your current version of "NewtonAbsTolerance") and then be interested in a maximum shift in saturations (1.E-10). ---------- More information can be found at the following URL: http://www.dumux.org/flyspray/index.php?do=details&task_id=238#comment498 You are receiving this message because you have requested it from the Flyspray bugtracking system. If you did not expect this message or don't want to receive mails in future, you can change your notification settings at the URL shown above. _______________________________________________ Dumux mailing list [email protected] https://listserv.uni-stuttgart.de/mailman/listinfo/dumux
