Hi Thibault, I think that you are almost there with your implementation. There are a few more things to do to get it working.
- First, use an ImplciitSourceTerm rather than a TransientTerm to represent "p" in the pressure equation. - Secondly, use a CentralDifferenceConvectionTerm in the momentum equations to represent dp/dx etc. This will give you the implicit coupling. Also, maybe, in the roE equation, though that is more complicated. - Thirdly, as this is non-linear, you also need an extra non-linear loop at each time step. - Fourthly, if you can't get this working in a coupled manner. Maybe try uncoupling and solving each equation separately, but use the non-linear loop mentioned above. Only when that is working you should start coupling terms one by one. Cheers, Daniel On Thu, May 18, 2017 at 5:55 AM, Thibault Bridel-Bertomeu <thibault.bridellel...@gmail.com> wrote: > Hello Daniel, > > Thank you for the paper and the script - I am afraid it will take me some > time though, its impressive and long work !! > > Regarding the equations, I think I was not clear enough in my previous > explanations, I apologize. > In substance, I have 4 variables : ro, roU, roV and roE. They are density, > velocity along X, velocity along Y and energy. > I also have 4 differential equations : > > dro/dt + nabla.(ro*[U,V]) = 0 > droU/dt + nabla.(roU*[U,V]) = -dp / dx > droV/dt + nabla.(roV*[U,V]) = -dp / dy > droE/dt + nabla.(roE*[U,V]) = - d(p*(roU/ro))/dx - d(p*(roV/ro))/dy > > As you can see, they are written with a fifth variable, p, for pressure, > that is related to the others by : > > p = (gamma-1.0)*roE - 0.5*(gamma-1.0)*(roU**2 + roV**2)/ro > > this is what I call the equation of state, it is not differential it is just > algebraic. > > I wager the differential equations above are not the most complex you have > seen or implemented in FiPy, and I think I succeeded, although of course, > since the whole thing does not work, I cannot be sure. But then I am stuck > with that non-differential equation that I would have to solve with the four > differential (?) to close the system … > > Can you see what I am stuck with ? > Also, could you please elaborate on the last paragraph of your previous > e-mail ? « If you do include … » I am not sure I get why you speak of > linearization and relaxation ? > > I attach the latest version of my non-working script .. > > Thanks for the help > > Best, > > Thibault -- Daniel Wheeler _______________________________________________ fipy mailing list fipy@nist.gov http://www.ctcms.nist.gov/fipy [ NIST internal ONLY: https://email.nist.gov/mailman/listinfo/fipy ]
