Dear Fei Gao, Thank you for your question and interest in using Nektar++, you need to add a "Filter" section at the end of your session file: <FILTERS> <FILTER TYPE="AverageFields"> <PARAM NAME="OutputFile">MyAverageField</PARAM> <PARAM NAME="OutputFrequency">10000</PARAM> <PARAM NAME="SampleFrequency"> 1 </PARAM> </FILTER> <FILTER TYPE="AeroForces"> <PARAM NAME="OutputFile">DragLift</PARAM> <PARAM NAME="OutputFrequency">1</PARAM> <PARAM NAME="Boundary">B[0]</PARAM> </FILTER> </FILTERS> Please see sections "3.5.22 Time-averaged fields" and "3.5.2 Aerodynamic forces", although it says that the "AeroForces" filter does not work with the compressible solver I got it to work with the above. I hope this answers your query. Thanks, Guglielmo ________________________________ From: nektar-users-bounces@imperial.ac.uk <nektar-users-bounces@imperial.ac.uk> on behalf of Gao <feigao2024@126.com> Sent: 18 December 2024 02:11 To: nektar-users <nektar-users@imperial.ac.uk> Subject: [Nektar-users] Questions about Nektar++ This email from feigao2024@126.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. Hello, everyone I have two questions about using Nektar++. First, When I change the initial value to the std file of the previous time step, then the instantaneous result (5.chk, 6.chk...) can come out, but the averge field result didn't appear. Is this normal? And the average field file is output only when the calculation is complete, is the mean field file at this point the result of a continuation run? Second, I am trying to monitor aerodynamic forces in the CompressibleFlowSolver. But it seems that the FilterAeroForces supports only the incompressible solver. Is there any other way to get the aerodynamic force over time? Thanks a lot. With best regards