Still a long way to go... Would you please tell me how to view the "truth solve" solution?
Gauvain 2018-02-27 22:00 GMT+08:00 David Knezevic <david.kneze...@akselos.com>: > On Tue, Feb 27, 2018 at 8:55 AM, 吴家桦Gauvain <causegauv...@gmail.com> > wrote: > >> Thanks for replying. >> >> I did omit the inertia terms in my PDE. Regarding the greedy convergence >> of 7 parameter transient case, the maximum error bound decreases as usual, >> from about 40000 to 0.00197 but the result is abnormal like what is >> described in my first mail. In fact, 3 parameter (thermal conditions) >> transient case works well and so does 7 parameter steady case. The problem >> arises when I attempt to combine them together by replacing the assembly >> function of the stiffness matrix in 3 parameter transient case with that of >> 7 parameter steady case. >> > > Sounds like you need to do some debugging... e.g. set parameters to have > min=max and see if it's still abnormal, or view the "truth solve" solution > or other things like that to try to identify where the problem is. > > David > > > > >> 2018-02-27 21:21 GMT+08:00 David Knezevic <david.kneze...@akselos.com>: >> >>> On Tue, Feb 27, 2018 at 4:03 AM, 吴家桦Gauvain <causegauv...@gmail.com> >>> wrote: >>> >>>> Hi all, >>>> >>>> I am trying to make a transient thermoelastic RB model. Both Internal >>>> heat >>>> flux and external heat exchange described by Newton's law of >>>> cooling(Robin >>>> boundary condition) are considered. It works well when the three thermal >>>> conditions (heat flux, heat transfer coefficient and ambient >>>> temperature) >>>> are chosen as parameters. However, abnormal results are observed when >>>> the >>>> material properties (Young's modulus, Poisson's ratio, thermal expansion >>>> coefficient and heat conductivity) are added as parameters: Three >>>> displacement components remain 0 and the temperature increases >>>> drastically >>>> as the time goes by. What's more, I notice that the difference between >>>> the >>>> first and the second POD eigenvalues is extremely large: >>>> >>>> POD Eigenvalues: >>>> eigenvalue 0 = 4.4536e+08 >>>> eigenvalue 1 = 2.45303e-07 >>>> ... >>>> last eigenvalue = -1.90536e-07 >>>> >>>> The matrix assembly should not pose problem because it runs well in >>>> steady >>>> case and I simply copy the assembly functions without any modification. >>>> Thus I am really confused and I cannot figure out where the problem is. >>>> Could you give me some suggestions? Thanks a lot. >>>> >>> >>> Good to hear that it works well in the steady case. >>> >>> Regarding the transient case, I have a few comments: >>> >>> - The default implementation for transient RB that is used in the >>> examples is intended for parabolic PDEs, like the heat equation. I guess >>> your PDE is parabolic since you omit the hyperbolic parts (i.e. the inertia >>> terms) from the elasticity part of the system? >>> >>> - 7 parameters is quite a lot of parameters, so you may just be having >>> trouble with greedy convergence? >>> >>> My main suggestion would be to try to get a simple transient problem >>> working first, then add more complexity to it until you reach the problem >>> that you're interested in, e.g. you could start with the heat equation and >>> then add elasticity terms. >>> >>> Regards, >>> David >>> >>> >>> >> >> >> -- >> > > -- *吴家桦 Gauvain* *Mobile:13316300622* *Email:g <gauvai...@foxmail.com>auvain.wujia...@gmail.com <auvain.wujia...@gmail.com>* 中山大学中法核工程与技术学院学生 Institut Franco-Chinois de l'Energie Nucléaire, L'université Sun Yat-sen ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Libmesh-users mailing list Libmesh-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/libmesh-users
