However if you use IMEX for strong coupling of the two physics solved in each field, then it means you need to write a single set of PDEs that covers everything, don’t you ? If I want to solve Euler equations in one PetscDS and heat equation in the other one, then I need to write a global set of equations to use the IMEX TS , right ?
Thanks, Thibault Le sam. 8 janv. 2022 à 20:00, Matthew Knepley <knep...@gmail.com> a écrit : > On Sat, Jan 8, 2022 at 1:30 PM Thibault Bridel-Bertomeu < > thibault.bridelberto...@gmail.com> wrote: > >> Yes I was wondering about different time steps as well because usually >> implicit integration moves much faster. >> But if it not implemented, then maybe going the « weak coupling » road >> with a sub-DM is the way. >> Can I ask how you proceed in the rocket engine code you are writing ? >> IMEX ? >> > > Right now it is IMEX, but we are explicitly substepping particles. Not > sure what the final thing will be. > > Thanks, > > Matt > > >> Thibault >> >> Le sam. 8 janv. 2022 à 19:22, Matthew Knepley <knep...@gmail.com> a >> écrit : >> >>> I do not know how. Right now, composable TS does not work all the way. >>> >>> Matt >>> >>> On Sat, Jan 8, 2022 at 1:03 PM Mark Adams <mfad...@lbl.gov> wrote: >>> >>>> Can you subcycle with IMEX? >>>> >>>> On Sat, Jan 8, 2022 at 10:58 AM Matthew Knepley <knep...@gmail.com> >>>> wrote: >>>> >>>>> On Sat, Jan 8, 2022 at 3:05 AM Thibault Bridel-Bertomeu < >>>>> thibault.bridelberto...@gmail.com> wrote: >>>>> >>>>>> Le ven. 7 janv. 2022 à 19:45, Thibault Bridel-Bertomeu < >>>>>> thibault.bridelberto...@gmail.com> a écrit : >>>>>> >>>>>>> Le ven. 7 janv. 2022 à 19:23, Matthew Knepley <knep...@gmail.com> a >>>>>>> écrit : >>>>>>> >>>>>>>> On Fri, Jan 7, 2022 at 12:58 PM Thibault Bridel-Bertomeu < >>>>>>>> thibault.bridelberto...@gmail.com> wrote: >>>>>>>> >>>>>>>>> >>>>>>>>> Le ven. 7 janv. 2022 à 14:54, Matthew Knepley <knep...@gmail.com> >>>>>>>>> a écrit : >>>>>>>>> >>>>>>>>>> On Fri, Jan 7, 2022 at 8:52 AM Thibault Bridel-Bertomeu < >>>>>>>>>> thibault.bridelberto...@gmail.com> wrote: >>>>>>>>>> >>>>>>>>>>> Hi Matthew, >>>>>>>>>>> >>>>>>>>>>> Le ven. 7 janv. 2022 à 14:44, Matthew Knepley <knep...@gmail.com> >>>>>>>>>>> a écrit : >>>>>>>>>>> >>>>>>>>>>>> On Fri, Jan 7, 2022 at 5:46 AM Thibault Bridel-Bertomeu < >>>>>>>>>>>> thibault.bridelberto...@gmail.com> wrote: >>>>>>>>>>>> >>>>>>>>>>>>> Dear all, >>>>>>>>>>>>> >>>>>>>>>>>>> First of, happy new year everyone !! All the best ! >>>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> Happy New Year! >>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>>> I am starting to draft a new project that will be about >>>>>>>>>>>>> fluid-structure interaction: in particular, the idea is to >>>>>>>>>>>>> compute the >>>>>>>>>>>>> Navier-Stokes (or Euler nevermind) flow around an object and _at >>>>>>>>>>>>> the same >>>>>>>>>>>>> time_ compute the heat equation inside the object. >>>>>>>>>>>>> So basically, I am thinking a mesh of the fluid and a mesh of >>>>>>>>>>>>> the object, both meshes being linked at the fluid - solid >>>>>>>>>>>>> interface. >>>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> First question: Are these meshes intended to match on the >>>>>>>>>>>> interface? If not, this sounds like overset grids or immersed >>>>>>>>>>>> boundary/interface methods. In this case, more than one mesh makes >>>>>>>>>>>> sense to >>>>>>>>>>>> me. If they are intended to match, then I would advocate a single >>>>>>>>>>>> mesh with >>>>>>>>>>>> multiple problems defined on it. I have experimented with this, >>>>>>>>>>>> for example >>>>>>>>>>>> see SNES ex23 where I have a field in only part of the domain. I >>>>>>>>>>>> have a >>>>>>>>>>>> large project to do exactly this in a rocket engine now. >>>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> Yes the way I see it is more of a single mesh with two distinct >>>>>>>>>>> regions to distinguish between the fluid and the solid. I was >>>>>>>>>>> talking about >>>>>>>>>>> two meshes to try and explain my vision but it seems like it was >>>>>>>>>>> unclear. >>>>>>>>>>> Imagine if you wish a rectangular box with a sphere inclusion: >>>>>>>>>>> the sphere would be tagged as a solid and the rest of the domain as >>>>>>>>>>> fluid. >>>>>>>>>>> Using Gmsh volumes for instance. >>>>>>>>>>> Ill check out the SNES example ! Thanks ! >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>>> First (Matthew maybe ?) do you think it is something that >>>>>>>>>>>>> could be done using two DMPlex's that would somehow be spawned >>>>>>>>>>>>> from reading >>>>>>>>>>>>> a Gmsh mesh with two volumes ? >>>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> You can take a mesh and filter out part of it with >>>>>>>>>>>> DMPlexFilter(). That is not used much so I may have to fix it to >>>>>>>>>>>> do what >>>>>>>>>>>> you want, but that should be easy. >>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>>> And on one DMPlex we would have finite volume for the fluid, >>>>>>>>>>>>> on the other finite elements for the heat eqn ? >>>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> I have done this exact thing on a single mesh. It should be no >>>>>>>>>>>> harder on two meshes if you go that route. >>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>>> Second, is it something that anyone in the community has ever >>>>>>>>>>>>> imagined doing with PETSc DMPlex's ? >>>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> Yes, I had a combined FV+FEM simulation of magma dynamics (I >>>>>>>>>>>> should make it an example), and currently we are doing FVM+FEM for >>>>>>>>>>>> simulation of a rocket engine. >>>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> Wow so it seems like it’s the exact same thing I would like to >>>>>>>>>>> achieve as the rocket engine example. >>>>>>>>>>> So you have a single mesh and two regions tagged differently, >>>>>>>>>>> and you use the DmPlexFilter to solve FVM and FEM separately ? >>>>>>>>>>> >>>>>>>>>> >>>>>>>>>> With a single mesh, you do not even need DMPlexFilter. You just >>>>>>>>>> use the labels that Gmsh gives you. I think we should be able to get >>>>>>>>>> it >>>>>>>>>> going in a straightforward way. >>>>>>>>>> >>>>>>>>> >>>>>>>>> Ok then ! Thanks ! I’ll give it a shot and see what happens ! >>>>>>>>> Setting up the FVM and FEM discretizations will pass by DMSetField >>>>>>>>> right ? With a single mesh tagged with two different regions, it >>>>>>>>> should >>>>>>>>> show up as two fields, is that correct ? >>>>>>>>> >>>>>>>> >>>>>>>> Yes, the idea is as follows. Each field also has a label argument >>>>>>>> that is the support of the field in the domain. Then we create PetscDS >>>>>>>> objects for each >>>>>>>> separate set of overlapping fields. The current algorithm is not >>>>>>>> complete I think, so let me know if this step fails. >>>>>>>> >>>>>>> >>>>>>> Ok, thanks. >>>>>>> I’ll let you know and share snippets when I have something started ! >>>>>>> >>>>>>> Talk soon ! Thanks ! >>>>>>> >>>>>> >>>>>> Hi Matthew, >>>>>> >>>>>> I thought about a little something else : what about setting two >>>>>> different TS, one for each field of the DM ? Most probably the fluid part >>>>>> would be solved with an explicit time stepping whereas the solid part >>>>>> with >>>>>> the heat equation would benefit from implicit time stepping. TSSetDM does >>>>>> not allow a field specification, is there a way to hack that so that each >>>>>> field has its own TS ? >>>>>> >>>>> >>>>> I see at least two options here: >>>>> >>>>> 1. Split the problems: >>>>> >>>>> You can use DMCreateSubDM() to split off part of a problem and use >>>>> a solver on that. I have done this for problems with weak coupling. >>>>> >>>>> 2. Use IMEX >>>>> >>>>> For strong coupling, I have used the IMEX TSes in PETSc. You put >>>>> the explicit terms in the RHS, and the implicit in the IFunction. >>>>> >>>>> Thanks, >>>>> >>>>> Matt >>>>> >>>>> >>>>>> Thanks >>>>>> >>>>>> Thibault >>>>>> >>>>>> >>>>>>> Thibault >>>>>>> >>>>>>> >>>>>>>> Thanks, >>>>>>>> >>>>>>>> Matt >>>>>>>> >>>>>>>> >>>>>>>>> Thanks, >>>>>>>>> >>>>>>>>> Thibault >>>>>>>>> >>>>>>>>> >>>>>>>>>> Thanks, >>>>>>>>>> >>>>>>>>>> Matt >>>>>>>>>> >>>>>>>>>> >>>>>>>>>>> Thanks ! >>>>>>>>>>> >>>>>>>>>>> Thibault >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>>> Thanks, >>>>>>>>>>>> >>>>>>>>>>>> Matt >>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>>> As I said it is very prospective, I just wanted to have your >>>>>>>>>>>>> opinion !! >>>>>>>>>>>>> >>>>>>>>>>>>> Thanks very much in advance everyone !! >>>>>>>>>>>>> >>>>>>>>>>>>> Cheers, >>>>>>>>>>>>> Thibault >>>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> -- >>>>>>>>>>>> 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 >>>>>>>>>>>> >>>>>>>>>>>> https://www.cse.buffalo.edu/~knepley/ >>>>>>>>>>>> <http://www.cse.buffalo.edu/~knepley/> >>>>>>>>>>>> >>>>>>>>>>> -- >>>>>>>>>>> Thibault Bridel-Bertomeu >>>>>>>>>>> — >>>>>>>>>>> Eng, MSc, PhD >>>>>>>>>>> Research Engineer >>>>>>>>>>> CEA/CESTA >>>>>>>>>>> 33114 LE BARP >>>>>>>>>>> Tel.: (+33)557046924 >>>>>>>>>>> Mob.: (+33)611025322 >>>>>>>>>>> Mail: thibault.bridelberto...@gmail.com >>>>>>>>>>> >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> -- >>>>>>>>>> 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 >>>>>>>>>> >>>>>>>>>> https://www.cse.buffalo.edu/~knepley/ >>>>>>>>>> <http://www.cse.buffalo.edu/~knepley/> >>>>>>>>>> >>>>>>>>> -- >>>>>>>>> Thibault Bridel-Bertomeu >>>>>>>>> — >>>>>>>>> Eng, MSc, PhD >>>>>>>>> Research Engineer >>>>>>>>> CEA/CESTA >>>>>>>>> 33114 LE BARP >>>>>>>>> Tel.: (+33)557046924 >>>>>>>>> Mob.: (+33)611025322 >>>>>>>>> Mail: thibault.bridelberto...@gmail.com >>>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> -- >>>>>>>> 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 >>>>>>>> >>>>>>>> https://www.cse.buffalo.edu/~knepley/ >>>>>>>> <http://www.cse.buffalo.edu/~knepley/> >>>>>>>> >>>>>>> -- >>>>>>> Thibault Bridel-Bertomeu >>>>>>> — >>>>>>> Eng, MSc, PhD >>>>>>> Research Engineer >>>>>>> CEA/CESTA >>>>>>> 33114 LE BARP >>>>>>> Tel.: (+33)557046924 >>>>>>> Mob.: (+33)611025322 >>>>>>> Mail: thibault.bridelberto...@gmail.com >>>>>>> >>>>>> -- >>>>>> Thibault Bridel-Bertomeu >>>>>> — >>>>>> Eng, MSc, PhD >>>>>> Research Engineer >>>>>> CEA/CESTA >>>>>> 33114 LE BARP >>>>>> Tel.: (+33)557046924 >>>>>> Mob.: (+33)611025322 >>>>>> Mail: thibault.bridelberto...@gmail.com >>>>>> >>>>> >>>>> >>>>> -- >>>>> 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 >>>>> >>>>> https://www.cse.buffalo.edu/~knepley/ >>>>> <http://www.cse.buffalo.edu/~knepley/> >>>>> >>>> >>> >>> -- >>> 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 >>> >>> https://www.cse.buffalo.edu/~knepley/ >>> <http://www.cse.buffalo.edu/~knepley/> >>> >> -- >> Thibault Bridel-Bertomeu >> — >> Eng, MSc, PhD >> Research Engineer >> CEA/CESTA >> 33114 LE BARP >> Tel.: (+33)557046924 >> Mob.: (+33)611025322 >> Mail: thibault.bridelberto...@gmail.com >> > > > -- > 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 > > https://www.cse.buffalo.edu/~knepley/ > <http://www.cse.buffalo.edu/~knepley/> > -- Thibault Bridel-Bertomeu — Eng, MSc, PhD Research Engineer CEA/CESTA 33114 LE BARP Tel.: (+33)557046924 Mob.: (+33)611025322 Mail: thibault.bridelberto...@gmail.com
