Dear Petsc Users I wrote a code in 2D solving PF equations for solidification of alloys. I have two variables in the equations 1-non-dimensional concentration (U) 2- order parameter (p). Everything is fine with this code. When I change the code to 3D, the code has convergence problems which I cannot solve it. I know the term which is causing problem is a term in the equation for U: (dp/dt)*(Pxx+Pyy+Pzz) where Pxx,Pyy,Pzz are the second derivative of order parameter in x,y,z, respectively.
When I eliminate this term, the results of 2D and 3D are close to each other. But adding that term the time step should be reduced a lot to obtain convergence, otherwise the timestep does not converge. I have no idea how I should solve this problem. I solve the equations considering (I chose based on suggestions of Moose for solving Cahn-hillard) -ts_type bdf -ts_bdf_adapt -pc_type bjacobi -snes_linesearch_type l2 -snes_type newtontr -ksp_type gmres -ksp_gmres_restart 1001 -sub_pc_type ilu -sub_ksp_type preonly Would you please help me solve this issue? Best, sepideh
