Hi Tongkuai, I am not sure what's the problem, but Nektar++ should output correct force, this has been validated by numerous work. May I know the nektar++ version you are using and have a look at your grid and Reynolds number? Cheers Ankang -----Original Messages----- From:"王同快" <22224016@zju.edu.cn> Sent Time:2023-06-14 10:58:44 (Wednesday) To: nektar-users@imperial.ac.uk Cc: Subject: [Nektar-users] result problems in Aerodynamics forces | This email from 22224016@zju.edu.cn 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 to disable email stamping for this address. | Dear All, I've calculated the drag forces on a cylinder and a sphere and compared the results with the standard drag model and find that the force in .fce file is approximately 8 times larger than the model prediction.And it is also the case for lift force and momentum.I wonder if there is something wrong with the force integral code. Kind regards Wang