solid body rotation of grid

Duncan_vdH · March 21, 2017, 16:41

We are working on a case with imposed rotational motion of a partially submerged solid body. With the imposed motion, the grid deformation is controlled by the diffusivity model.

It turns out to be very challenging to avoid grid folding in the inner part of the boundary layer cells. Even the cells adjacent to the boundary are slightly deformed,
nearly irrespective of the chosen diffusivity model.

In the 6DOF solver you can exclude deformation inside an 'inner radius'.
Is something similar possible for imposed motion? So concentrate all grid deformation
outside the boundary layer?

Thanks in advance,
Duncan

tomf · March 22, 2017, 13:57

Hi Duncan,

It sounds like you could have a sliding AMI interface to rotate only a part of the domain, like in the propeller tutorial, or is there a reason that this is not possible?

If so, please elaborate on the problem a bit.

Regards,
Tom

Duncan_vdH · March 22, 2017, 14:03

Hi Tom,

Thank you for replying.

We have used a sliding mesh in the past, but found that the sliding mesh creates disturbances in the interface (the free surface interface): small artificial waves due to inaccuracies in the interpolation I think.

The geometry of the solid body that rotates has sharp corners, and it is exactly at the corners the grid folds. I was wondering why no nonOrthogonal corrections are applied for solution of the Poisson equation for the displacement.

An alternative would be to use the cell displacement from the 6dof solver but with prescribed motion. However, it is unclear how to set up such a case.

Best,
Duncan

March 21, 2017, 16:41	solid body rotation of grid	#1
Duncan_vdH New Member Duncan Roy van der Heul Join Date: May 2010 Posts: 26 Rep Power: 16	We are working on a case with imposed rotational motion of a partially submerged solid body. With the imposed motion, the grid deformation is controlled by the diffusivity model. It turns out to be very challenging to avoid grid folding in the inner part of the boundary layer cells. Even the cells adjacent to the boundary are slightly deformed, nearly irrespective of the chosen diffusivity model. In the 6DOF solver you can exclude deformation inside an 'inner radius'. Is something similar possible for imposed motion? So concentrate all grid deformation outside the boundary layer? Thanks in advance, Duncan

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March 22, 2017, 13:57		#2
tomf Senior Member Tom Fahner Join Date: Mar 2009 Location: Breda, Netherlands Posts: 638 Rep Power: 32	Hi Duncan, It sounds like you could have a sliding AMI interface to rotate only a part of the domain, like in the propeller tutorial, or is there a reason that this is not possible? If so, please elaborate on the problem a bit. Regards, Tom

March 22, 2017, 14:03		#3
Duncan_vdH New Member Duncan Roy van der Heul Join Date: May 2010 Posts: 26 Rep Power: 16	Hi Tom, Thank you for replying. We have used a sliding mesh in the past, but found that the sliding mesh creates disturbances in the interface (the free surface interface): small artificial waves due to inaccuracies in the interpolation I think. The geometry of the solid body that rotates has sharp corners, and it is exactly at the corners the grid folds. I was wondering why no nonOrthogonal corrections are applied for solution of the Poisson equation for the displacement. An alternative would be to use the cell displacement from the 6dof solver but with prescribed motion. However, it is unclear how to set up such a case. Best, Duncan