Hello,

I would like to use the integral filter in nektar++ but I am experiencing some difficulties. As a test case for testing the filter I am using a slightly modified version of the forward step case from the tutorials - I have modified the inlet to 2 length units high instead of just 1. Besides, at the inlet I have set the horizontal velocity component to 1, I no longer use a parabolic profile. Then, I have defined the Integral filter to monitor the composites 2 and 3, which correspond to the "wall"  and "inlet".

Regarding the results:

At the "wall" composite, non-slip boundary conditions are applied, meaning that velocity is set to zero. However, the integral filter outputs values quite different from zero.

For the "inlet" composite, The output of the integral filter for the vertical velocity provides a value quite close to zero, O(-7), but not exactly zero. I understand that there might be numerical errors in the calculations but I do not know if this accuracy (or error) is expected. Regarding the integral results for the horizontal velocity, I would expect the output to be a constant value of 2 - the horizontal velocity is 1 and the height of the inlet is 2. However, it outputs a value of 3.1568.

Could you please indicate to me whether I am misinterpreting the functionality of the integral filter? Have I maybe incorrectly set certain parameters?

I enclose the session and mesh files.

Thank you in advance.

Cheers,

Guillermo