On Wed, Oct 11, 2023 at 1:03 PM Jed Brown <[email protected]> wrote:
> I don't see an attachment, but his thesis used conservative variables and > defined an effective length scale in a way that seemed to assume constant > shape function gradients. I'm not aware of systematic literature comparing > the covariant and contravariant length measures on anisotropic meshes, but > I believe most people working in the Shakib/Hughes approach use the > covariant measure. Our docs have a brief discussion of this choice. > > https://libceed.org/en/latest/examples/fluids/#equation-eq-peclet > > Matt, I don't understand how the second derivative comes into play as a > length measure on anistropic meshes -- the second derivatives can be > uniformly zero and yet you still need a length measure. > I was talking about the usual SUPG where we just penalize the true residual. Matt > Brandon Denton via petsc-users <[email protected]> writes: > > > I was thinking about trying to implement Ben Kirk's approach to > Navier-Stokes (see attached paper; Section 5). His approach uses these > quantities to align the orientation of the unstructured element/cell with > the fluid velocity to apply the stabilization/upwinding and to detect > shocks. > > > > If you have an example of the approach you mentioned, could you please > send it over so I can review it? > > > > On Oct 11, 2023 6:02 AM, Matthew Knepley <[email protected]> wrote: > > On Tue, Oct 10, 2023 at 9:34 PM Brandon Denton via petsc-users < > [email protected]<mailto:[email protected]>> wrote: > > Good Evening, > > > > I am looking to implement a form of Navier-Stokes with SUPG > Stabilization and shock capturing using PETSc's FEM infrastructure. In this > implementation, I need access to the cell's shape function gradients and > natural coordinate gradients for calculations within the point-wise > residual calculations. How do I get these quantities at the quadrature > points? The signatures for fo and f1 don't seem to contain this information. > > > > Are you sure you need those? Darsh and I implemented SUPG without that. > You would need local second derivative information, which you can get using > -dm_ds_jet_degree 2. If you check in an example, I can go over it. > > > > Thanks, > > > > Matt > > > > Thank you in advance for your time. > > Brandon > > > > > > -- > > 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/>
