Hi Dauood, Looking at the user-guide, it explains that you should first define your source term as a forcing function. The <FORCING> tag should be place outside of the <CONDITION> tag. Then, within the <CONDITION> tag, you define the source function you want to. In the <FUNCTION> tag, you can define the pressure and velocity fields. Best regards, João. From: nektar-users-bounces@imperial.ac.uk <nektar-users-bounces@imperial.ac.uk> on behalf of dauood Tariq <dgtariq10@gmail.com> Date: Monday, 6 May 2024 at 20:55 To: nektar-users <nektar-users@imperial.ac.uk> Subject: [Nektar-users] Acoustic solver Source term This email from dgtariq10@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. Hi, I am trying to understand the source term provided in the user guide however the equation for the source term is very confusing and I cannot find any information on it. I would appreciate it. Regards, Dauood