Hi Syavash You could use FieldConvert’s WSS module. For instance, if the wall boundary ID is 0, FieldConvert -m wss:bnd=0 <mesh.xml> <session.xml> <time-averaged.fld> <time-averaged-wss.fld> The output fld will either be a 1D/2D field of wss values on the boundary ID for a 2D/3D flow field. If you wish to compute mean of the wss, you can use FieldConvert -m mean with the appropriate 1D/2D mesh file of the boundary obtained using Nekmesh -m extract. Hope this helps Cheers Chi Hin Get Outlook for iOS<https://aka.ms/o0ukef> ________________________________ From: nektar-users-bounces@imperial.ac.uk <nektar-users-bounces@imperial.ac.uk> on behalf of Ehsan Asgari <eh.asgari@gmail.com> Sent: Tuesday, June 6, 2023 8:07:43 AM To: nektar-users <nektar-users@imperial.ac.uk> Subject: [Nektar-users] Calculating time-averaged wall shear stress This email from eh.asgari@gmail.com 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 have a time-averaged field, say "time-average.fld". How should I proceed to calculate time-averaged wall shear stress? I was wondering if I need to use "wss" first. Kind regards syavash