I solve with truth_solve and find the result is also bizarre, which is the same as the previous ones. I may have to check the matrix assembly. Thank you so much for your help.
Gauvain 2018-02-28 0:44 GMT+08:00 David Knezevic <david.kneze...@akselos.com>: > On Tue, Feb 27, 2018 at 9:48 AM, 吴家桦Gauvain <causegauv...@gmail.com> > wrote: > >> Still a long way to go... Would you please tell me how to view the "truth >> solve" solution? >> > > RBConstruction::truth_solve take an int argument. If that's negative then > it doesn't plot. If it's positive then it plots the "truth solution" in the > steady-state case. In the transient case, if you set the int to be 10, for > example, then it will plot every 10th time step. > > I suggest you do some solves with truth_solve directly and look at the > solution since that will allow you to set up specific parameters and do a > solve and check that it looks right. Note that train_reduced_basis also > calls truth_solve and it has the int argument set to -1 so that it doesn't > plot anything. > > David > > P.S. As usual, make sure you're using a direct solver (e.g. MUMPS) during > debugging to eliminate incomplete solver convergence as one possible source > of problems. > > > 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 <(331)%20630-0622>* >> *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 >> > > -- *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
