On Wed, Apr 5, 2017 at 11:50 AM, Ingo Gaertner <[email protected]> wrote:
> Hi Jed, > thank you for your reply. Two followup questions below: > > 2017-04-04 22:18 GMT+02:00 Jed Brown <[email protected]>: > >> Ingo Gaertner <[email protected]> writes: >> >> > We have never talked about Riemann solvers in our CFD course, and I >> don't >> > understand what's going on in ex11. >> > However, if you could answer a few of my questions, you'll give me a >> good >> > start with PETSc. For the simple poisson problem that I am trying to >> > implement, I have to discretize div(k grad u) integrated over each FV >> cell, >> > where k is the known diffusivity, and u is the vector to solve for. >> >> Note that ex11 solves hyperbolic conservation laws, but you are solving >> an elliptic equation. >> > > I begin to understand. Petscs FVM methods don't provide a FVM library that > can be used to implement the FV control volume approach (see Ferziger) for > general CFD problems? They are around just because they have been used to > tackle one or two specific problems, is this correct? > I thought they could be used similar to the OpenFvm or OpenFoam libraries > which seem to solve Poisson, Navier-Stokes, Euler and other problems. If > such methods have not been prepared for Petsc, I'll just follow Ferzigers > book and start my work on a lower level than I thought would be necessary. > More work, more fun :) > Yes, that is correct. As a side note, I think using FV to solve an elliptic equation should be a felony. Continuous FEM is excellent for this, whereas FV needs a variety of twisted hacks and is always worse in terms of computation and accuracy. Hyperbolic problems are what FV is designed for and I don't think I would ever support it for anything but that. Thanks, Matt > > (My second question is more general about the PETSc installation. When I >> > configure PETSc with "--prefix=/somewhere --download-triangle >> > --download-parmetis" etc., these extra libraries are built correctly >> during >> > the make step, but they are not copied to /somewhere during the "make >> > install" step. >> >> Where are they put during configure? >> > > My bad, Petsc installation works as expected. But the build system that I > am using is doing something weird. I'll have to find out, what's going > wrong there, but it is not related to Petsc. > > Thank you! > Ingo > > > > <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail> > Virenfrei. > www.avast.com > <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail> > <#m_-9031669297911553285_DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2> > -- What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead. -- Norbert Wiener
