Hi Amitvikram, What sort of mesh were you running? Perhaps this is a 3D element we have not fully tested ? Cheers, Spencer Sent from my iPhone On 27 Feb 2019, at 07:09, Amitvikram Dutta <amitvdutta23@gmail.com<mailto:amitvdutta23@gmail.com>> wrote: Hi all, I'm testing out the Robin type BCs for the outflow as given in the user guide. Which takes the form of the following <R VAR="u" USERDEFINEDTYPE="HOutflow" VALUE="0" PRIMCOEFF="D0/TimeStep"/> <R VAR="v" USERDEFINEDTYPE="HOutflow" VALUE="0" PRIMCOEFF="D0/TimeStep"/> <R VAR="p" USERDEFINEDTYPE="HOutflow" VALUE="0" PRIMCOEFF="1.0/(D0*Kinvis)"/> Upon startup, this gives the error Fatal : Level 0 assertion violation Could not identify matrix type from dimension I havent come across this error before. Could someone point out what the error is? SIncerely, -- Amitvikram Dutta Graduate Research Assistant Fluid Mechanics Research Lab Multi-Physics Interaction Lab University of Waterloo _______________________________________________ Nektar-users mailing list Nektar-users@imperial.ac.uk<mailto:Nektar-users@imperial.ac.uk> https://mailman.ic.ac.uk/mailman/listinfo/nektar-users