Hi Selman, There is not roughness parameter in nektar. You can generate a set of mesh over a rough wall in GMSH. You can use the mapping method to transform a plane wall to a rough wall, but the Jacobian of the mapping would introduce more aliasing error. Cheers Ankang -----Original Messages----- From:"Selman BAYSAL" <selmanbaysal@comu.edu.tr> Sent Time:2023-05-29 16:30:38 (Monday) To: nektar-users@imperial.ac.uk Cc: Subject: [Nektar-users] Implementing rough wall condition | This email from selmanbaysal@comu.edu.tr 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 to disable email stamping for this address. | Dear all, I am relatively new to CFD and Nektar++. Although there are much studies perfomed by Nektar++ on flows over rough surface/bed, I could not find detailed information on how to define a rough surface. I intended to define a rough surface/boundary (not a single roughness element or hump), and then, to investigate the boundary layer developed over this surface. For this purpose, do I need an external program like GMSH or is there any parameters (such as Nikuradse equivalent sand roughness or roughness height) or modules implemented in Nektar++? Any help would be greatly appreciated! Many thanks, Selman Baysal R. A. in Hydraulics Dept. of Civil Eng'g Çanakkale Onsekiz Mart University -- ITU Civil Eng., BSc. ITU Coastal Sci. & Eng., MSc.