Thanks a lot, Hong. I would think if one use BDF or backward Euler for incompressible Naiver Stokes, it should work with the index 2 equation. Why do you think it will not work? Or maybe you were talking about a general usage.
INS is not my usage but I am still curious. We have some unconventional constraint equation. Qi On Feb 15, 2022, at 8:51 AM, Zhang, Hong <[email protected]<mailto:[email protected]>> wrote: Hi Qi, The index-2 DAE cannot be solved directly with ARK or implicit methods such as backward Euler and Crank-Nicolson. You need to convert the system to an index-1 DAE as illustrated in the documentation. Hong (Mr.) On Feb 15, 2022, at 9:43 AM, Tang, Qi <[email protected]<mailto:[email protected]>> wrote: Hi, Does PETSc’s ARK directly apply to Hessenberg Index-2 DAE? Do we need to perform a time derivative of the constraint equation by ourselves first? https://petsc.org/main/docs/manual/ts/#hessenberg-index-2-dae<https://urldefense.com/v3/__https://petsc.org/main/docs/manual/ts/*hessenberg-index-2-dae__;Iw!!HXCxUKc!kM_qeX09WwLuE991Vn6u85M0vDlNnqMA0Diuy84sqZawkGLr-MNDkYVisStQBA$> If we do not have to, do we expect to get high order in time? Thanks, Qi
