Hi Song, The Forcing terms are implemented in a C++ factory pattern. So it is possible to write a user defined forcing and it should integrate into the solver. We are trying to catch up on how to develop things like this but unfortunately we do not have documentation on this yet. Are you familiar with factory patterns? Cheers, Spencer. On 4 Mar 2017, at 13:00, Song Ke <songke21@outlook.com<mailto:songke21@outlook.com>> wrote: Hi Douglas: Thanks for your answer. I am testing a new case following your advise. Another problem. Sometimes the my source term model may be too complicate to be write in xml files as a formula or expression. I have to write c++ code for this model. Is the only solution to change the nektar source code? Regards, Song Ke _______________________________________________ Nektar-users mailing list Nektar-users@imperial.ac.uk<mailto:Nektar-users@imperial.ac.uk> https://mailman.ic.ac.uk/mailman/listinfo/nektar-users Spencer Sherwin McLaren Racing/Royal Academy of Engineering Research Chair, Professor of Computational Fluid Mechanics, Department of Aeronautics, Imperial College London South Kensington Campus London SW7 2AZ s.sherwin@imperial.ac.uk<mailto:s.sherwin@imperial.ac.uk> +44 (0) 20 759 45052