Huge displacement after using rbf-thin-plate-splines

Hi everyone,

I was trying to use another mapping method instead of neares-neighbor mapping.

Therefore I changed my config from:

<mapping:nearest-neighbor direction="write"
      	from="Fluid-Mesh"
        to="Solid-Mesh"
        constraint="conservative"/>
<mapping:nearest-neighbor direction="read"
      	from="Solid-Mesh"
        to="Fluid-Mesh"
        constraint="consistent"/>

to

<mapping:rbf-thin-plate-splines direction="write" from="Fluid-Mesh" to="Solid-Mesh" constraint="conservative" z-dead="true"/>
   	  <mapping:rbf-thin-plate-splines direction="read" from="Solid-Mesh" to="Fluid-Mesh" constraint="consistent" z-dead="true"/>

My mesh is something like this:

With nearest neighbor-mapping, everything is working fine, but switching to rbf, there is happening a huge displacement and therefore a crash of the simulation. Does anybody know, what could go wrong in this case?

Hi,

is it possible to add a picture of the nearest neighbor displacement and RBF displacement. Have you only tried thin plate splines? I would suggest also a compact RBF polynomial with a support radius of 3 or 4 times the mesh width. You can simply use

rbf-compact-polynomial-c0 support-radius="value"

Alternatively, is using z-dead=true actually required? Does it help to remove this?

1 Like

Hi,

sorry for the late reply.

Here you can see a picture of the fluid domain:

1st Timestep:

2nd Timestep (scaling is an issue - not wanted):

My solid domain is just a vertical beam which can bend along its vertical axis.
As it seems, a beam with 11 nodes on the y - axis can not be mapped with precice. Therefore, I just extruded the beam in x - direction 10 times.
I have now managed to get a deformation with rbf mapping but, it seems to map the data in a wrong way (see scaling issue).
I think my approach is wrong, but I do not know how to set up a mesh of a beam correctly.

Yes, since it is a 2D case, I have to mark the z-axis as dead.