******************* 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. ******************* Hello everyone, I would like to follow up on a post from Fri Apr 7 14:41:21 BST 2023 titled “Compute velocity gradient during runtime” that was made by another user. I am using the incompressible solver in Nektar++ 5.5.0 and need to calculate the Kolmogorov length scale for DNS analysis. For this, I rely on an estimation of the TKE dissipation rate which is defined using the fluctuation strain-rate tensor. In the post mentioned above, Ilteber suggested using the FieldConvert Checkpoints filter including the "gradient" module in order to extract field gradients. These could then be used to derive the fluctuation strain-rates and hence the dissipation in a post-processing step. However, in order to get a good estimate of the time-averaged dissipation, a sufficient amount of sampling points is needed. At this point, writing the whole domain seems quite excessive with regard to disk space. For this reason, I wonder whether there is maybe a clever way of combining the FieldConvert Checkpoints filter with e.g. the HistoryPoints filter in order to write only field gradients at specific points during runtime. I've seen some Nektar papers where the authors estimated the Kolmogorov length scale. Could anybody maybe comment on this? Thanks in advance! All the best Alex Sicher versendet mit [Proton Mail](https://proton.me/mail/home).