[petsc-users] about FD Jacobian for the new DAE solver

[Li, Zhisong (lizs)]

 Hi,

Last time I was suggested by Jed using the DAE solver to build my nonlinear CFD code based on TS. For incompressible N-S equations, I think it's difficult to derive the analytical Jacobian formulation, and we need a finite difference approximation or matrix-free method.

What I previously done was integrating the incompressible N-S equations into tutorial code ts/ex7.c  . It simply uses an argument "TSDefaultComputeJacobianColor" to finish the Jacobian issue. When I switch to TSSetIFunction() and TSSetIJacobian(), this argument doesn't work anymore. And if I remove all Jacobian-related lines and use -snes_mf command option, it prompts out error message "Must Set Jacobian!". Do you know how to resolve this for both methods?


Thank you.


Regards,



Zhisong Li
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