******************* This email 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. ******************* Dear all, I would like to have some clarification on how the Robin Boundary Conditions work on Nektar++. In particular, I would like to know how the normal derivative is calculated on a curved surface, where the normal to the surface is in the radial direction. Please find attached notes.pdf, where I try to explain myself a bit better. I hope my question it is clear enough. Thank you for your help. Kind regards, Silvia