Why my periodic boundary is not aligned with rotational motion axis?

nozhan

Dear All,

I have a system where I am trying to create a periodic boundary for a 90 angle space. I have added picture to explain my problem but for some reason, the axis of the rotational motion is in the correct position but the periodic boundary is located at a complete different place. i have tried to change the axis such that PB is in the correct place however PB rotates. I tired many things including rotating the geometry itself to change the local coor-system. Has anyone had this issue or have a suggestion for me? 

 

Stephen Cole

Hi,

 

The rotational boundary is linked to a linear rotation to define the axis, it looks like you have a rotation axis top right of the image however I assume this is offset or a different axis is used to have the cylindrical boundary at the centre of the geometry?

 

Ether way I would recommend setting up the rotation motion so that there is no offset, that the axis and point of action are the same and then you can relate the periodic boundary to this.

 

Or alternatively you can setup a new rotation kinematic with 0 rad/s angular velocity in the position that you want and assign the cylindrical boundary to this, it maybe the easiest way if your motion is already setup.  The periodic boundary just takes the axis position and doesn't consider the rotation velocity.  It does consider the length of the vector, if your case it looks like the boundary height is lower than the cylinder so particles can pass over the boundary.  I'd recommend making the vector longer to prevent this.

Regards

Stephen