inconsistent pointDisplacement for dynamic mesh

mo_na · January 31, 2017, 13:26

Dear foamers,

I am simulating the motion of a floating body with waveFoam (based on interFoam) using a dynamic mesh. I am using the sixDoFRigidBodyMotion solver.
I had to specify the outerDistance quite small with 0.08 because there is a second body really close to the other one. (If the outerDistance is bigger than the distance between the two bodies than boundary cells of the second body get highly distorted and the simulation crashes.)But I also can't really go smaller than 8cm because the motion is almost as big as that.
Now I am facing the following problem: The mesh morphing region stretches further in some directions than others. So it happened that in one direction it only stretches 2.8 cm and there I get a lot of nonOrthogonal faces and the simulation crashes. (See figures attached, both are from the same timestep)
Now I am wondering what this outerDistance refers to. Which position does it use for reference? Is the body moving faster than the morphing radius? Any ideas how to fix this?

I would really appreciate your help!
Cheers,
Mona

mo_na · February 20, 2017, 07:16

Ok, so it seems like the outerDistance refers to the initial position. Is there a way I can update the morphing region? Can the outerDistance be re-evaluated each time-step to refer to the current position?

fhjkfhjk · September 25, 2017, 12:38

I am not sure about this, but as far as I know, the thing that you can handle with the morphing mesh, is that diffusivity in your dynamicMesh file. I am not 100 % sure tho.

BTW, I am doing a simulation of a flow over a square cylinder, and it's rotated by the force from the flow. First time, the mesh badly morphed, and I changed the diffusiity to uniform to prevent the mesh from morphing. and It worked in my case.

So, you can take a look at the diffusivity parameters in OpenFOAM wiki.

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February 20, 2017, 07:16		#2
mo_na Member Mona Join Date: Mar 2016 Location: Berlin Posts: 49 Rep Power: 10	Ok, so it seems like the outerDistance refers to the initial position. Is there a way I can update the morphing region? Can the outerDistance be re-evaluated each time-step to refer to the current position?

September 25, 2017, 12:38		#3
fhjkfhjk New Member Dae-young(Dan) Join Date: Jan 2017 Location: South Korea Posts: 6 Rep Power: 9	I am not sure about this, but as far as I know, the thing that you can handle with the morphing mesh, is that diffusivity in your dynamicMesh file. I am not 100 % sure tho. BTW, I am doing a simulation of a flow over a square cylinder, and it's rotated by the force from the flow. First time, the mesh badly morphed, and I changed the diffusiity to uniform to prevent the mesh from morphing. and It worked in my case. So, you can take a look at the diffusivity parameters in OpenFOAM wiki.