James, are A(x,y), B(x,y) and C(x,y) three different variable functions for the PDE?
FIPY can solve at least when these three are equal. If it solves when they differ, I am not sure. Sergio Sergio Manzetti [ http://www.fjordforsk.no/logo_hr2.jpg ] [ http://www.fjordforsk.no/ | Fjordforsk AS ] [ http://www.fjordforsk.no/ | ] Midtun 6894 Vangsnes Norge Org.nr. 911 659 654 Tlf: +47 57695621 [ http://www.oekolab.com/ | Økolab ] | [ http://www.nanofact.no/ | Nanofactory ] | [ http://www.aq-lab.no/ | AQ-Lab ] | [ http://www.phap.no/ | FAP ] From: "James Pringle" <jprin...@unh.edu> To: "fipy" <fipy@nist.gov> Sent: Wednesday, May 31, 2017 9:31:51 PM Subject: solvers for elliptic equations with dominant lower order terms Dear all -- I need to solve a second order PDE in 2D of the form A(x,y)*(eta_xx+eta_yy)+B(x,y)*eta_x+C(x,y)*eta_y = 0 This is an advective diffusive balance, with B and C representing the advective velocities. BQ_BEGIN BQ_END Over much of the domain the low order terms dominate. For some geometries, the default solver I am using (SciPy LinearLUSolver) is having trouble find an answer (especially when the characteristics defined by B and C form loops . Does anyone have recommendations for how to choose a better solver? (I have blindly tried all the ones in SciPy, the ones besides LinearLUSolver do worse). And are there any hints on how to use preconditioners? There is discussion of preconditioners and Trilinnos, but I can't find hints on how one would choose to use them and when they might help. Pointers to the broader literature are welcome! Thank you, Jamie Pringle _______________________________________________ fipy mailing list fipy@nist.gov http://www.ctcms.nist.gov/fipy [ NIST internal ONLY: https://email.nist.gov/mailman/listinfo/fipy ]
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