HI Boyuan, Since this solver is using DG the boundary conditions are already implemented weakly through a Riemann solver. So inflow and outflow type boundary are automatically handled and we do not typically need the type of boundary condition you are mentioning below. Cheers, Spencer. On 15 Mar 2021, at 02:32, Boyuan Yu <boyuan.yu@mail.mcgill.ca<mailto:boyuan.yu@mail.mcgill.ca>> wrote: This email from boyuan.yu@mail.mcgill.ca<mailto:boyuan.yu@mail.mcgill.ca> originates from outside Imperial. Do not click on links and attachments unless you recognise the sender. If you trust the sender, add them to your safe senders list<https://spam.ic.ac.uk/SpamConsole/Senders.aspx> to disable email stamping for this address. Hello all, I am using ShallowWaterSolver and my application requires an outflow boundary condition. However, there seems no appropriate outflow boundary condition for ShallowWaterSolver (the "HOutflow" and "PressureOutflow" boundary conditions seem to only work for IncNavierStokesSolver). So how could the outflow boundary condition be implemented for ShallowWaterSolver? The "outflow" boundary condition here only requires that the field variables advected out of the domain without reflection using some kind of extrapolation. Thank you. Boyuan Yu _______________________________________________ Nektar-users mailing list Nektar-users@imperial.ac.uk<mailto:Nektar-users@imperial.ac.uk> https://mailman.ic.ac.uk/mailman/listinfo/nektar-users