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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
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Dear All,
How may I calculate the time-average of a gradient, for example velocity
gradient?
Kind regards
syavash
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Dear nektar++ users and developers.
Sorry to bother everyone here, however, I need some help the modifiedArnoldi solver.
In the linear stability solver, there are NUMSTEPS and KDIM to be filled in, what is the relationship between the setting of these two variables and the frequency of the unstable mode to be solved?
For example, if the frequency of the unstable mode is approximately 0.1 Hz (0.2pi for the circle frequency) and TIMESTEP = 0.002, should NUMSTEPS and KDIM be set relatively large or small in order to capture this unstable mode?
I wonder if anyone has any relevant experience in setting this up and I would appreciate any help.
Thanks again to the users and developers of nektar++.
Best Regards,
Wang Zhouyang
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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
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Dear All,
I have a time-averaged field, say "time-average.fld". How should I proceed
to calculate time-averaged wall shear stress? I was wondering if I need to
use "wss" first.
Kind regards
syavash