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Periodic boundary condition cannot be defined

Hello!

I am doing a CFD modelling of a plane with a pusher propeller attached to the back of the body, so I cannot introduce it alone in the cylinder of control (that will be afterwards the volume used to set the rotatory frame of reference), but with the final part of the body inside too. The propeller has only two blades, so if I want to establish a periodic boundary condition, it must be on surfaces spun 180º. But when I choose the option of periodic boundary condition, I select one of the two vertical faces as the source but no surface is then available to be selected.

How could I fix that?, or are there any other ways to define this boundary condition, taking advantage of the anti-symmetry?

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HyperMesh CFD

v2022.3

Accepted answers

acupro

There are existing development tickets for cases with large angles (like 180-deg) and axisymmetric periodicity - for both HyperWorks CFD and SimLab. With a simple case, I tried decreasing the included angle - and where 175-deg still didn't work, 170-deg did. Reducing the included angle a bit would likely introduce a small amount of error, but at least you could get your simulation running.

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acupro

The geometry appears not to be rotationally symmetric - not periodic. Towards the right side of that image, the edge above the axis line is different from the edge below the axis line. Thus, the mesh on those two faces will not be the same, thus periodicity cannot be applied. In other words, if you rotate that entire geometry 180-degrees about the axis, the new 'copy' does not look the same as the original, but more like a 'flipped' version of it. Thus, you will not be able to find a rotationally periodic match.

You may be able to cut part of those faces to get axisymmetric/rotational-periodic portions - but the part to the right, I guess more the main body, is more symmetric/mirror, but not rotationally periodic.

Rafal Blasczykowski

The geometry appears not to be rotationally symmetric - not periodic. Towards the right side of that image, the edge above the axis line is different from the edge below the axis line. Thus, the mesh on those two faces will not be the same, thus periodicity cannot be applied. In other words, if you rotate that entire geometry 180-degrees about the axis, the new 'copy' does not look the same as the original, but more like a 'flipped' version of it. Thus, you will not be able to find a rotationally periodic match.

You may be able to cut part of those faces to get axisymmetric/rotational-periodic portions - but the part to the right, I guess more the main body, is more symmetric/mirror, but not rotationally periodic.

Thank you for the answer.

Now I have subtracted a rotational-symmetric volume from the cylinder so that I can separate the final part of the plane (taking into account that there is no intersection between the propeller and any wall), which was the problem that caused the no periodicity. But now it is still not working because, as in the previous case, it does not recognize the target surface once selected the source one.

Just in case it could affect: the propeller is not symmetric due to the pitch and sweep, but in the end, none of them is so...

acupro