Hi Syavash, I'm not exactly familiar with computing viscous dissipation but I think that it could be computed with the enstrophy with the "energy" filter. There's a tutorial on Taylor Green's vortex on this, https://doc.nektar.info/tutorials/latest/incns/taylor-green-vortex/incns-tay... Hope this helps. Cheers, Chi Hin ________________________________ From: Ehsan Asgari <eh.asgari@gmail.com> Sent: 18 June 2023 11:56 To: Chan, Chi Hin <chi.chan19@imperial.ac.uk> Cc: nektar-users <nektar-users@imperial.ac.uk> Subject: Re: [Nektar-users] Time-average of a gradient Hi Chi Hin Thanks. You are right about the velocity gradient alone. Sorry, I didn't ask the right question. What can be done when we have a product of velocity gradients? More precisely, I need to calculate the TKE viscous dissipation term: nu*<s_ij s_ij>, where s_ij refers to the fluctuation strain rate tensor. I need this quantity to subsecuently calculate the Kolmogorov length scale. I see it calculated in a paper that has utilized Nektar++, but I have not a clear idea how it was done. Kind regards syavash On Sun, Jun 18, 2023, 14:03 Chan, Chi Hin <chi.chan19@imperial.ac.uk<mailto:chi.chan19@imperial.ac.uk>> wrote: Hi Syavash, You could use FieldConvert -m gradient on the time-averaged fields. Regards, Chi Hin Get Outlook for iOS<https://aka.ms/o0ukef> ________________________________ From: nektar-users-bounces@imperial.ac.uk<mailto:nektar-users-bounces@imperial.ac.uk> <nektar-users-bounces@imperial.ac.uk<mailto:nektar-users-bounces@imperial.ac.uk>> on behalf of Ehsan Asgari <eh.asgari@gmail.com<mailto:eh.asgari@gmail.com>> Sent: Saturday, June 17, 2023 8:20:29 PM To: nektar-users <nektar-users@imperial.ac.uk<mailto:nektar-users@imperial.ac.uk>> Subject: [Nektar-users] Time-average of a gradient This email from eh.asgari@gmail.com<mailto: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, How may I calculate the time-average of a gradient, for example velocity gradient? Kind regards syavash