Fluid Structure Interaction problem

Dear all,

I am trying to 2D model a solid body (circle) rotating in simple shear flow in a channel and I am using the fluid structure interaction module to try and solve it. I have followed the standard tutorial for deformation of a narrow vertical obstacle by horizontal channel flow and made changes to suit my needs. I have specified the following conditions in the fsi module.

- upper and lower walls have been specified as sliding walls moving opposite to each other so that the net velocity in channel is 0 an the solid body simply rotates without translation.
- mean inlet and outlet velocities have been specified as 0
- the body has been specified to be a linear elastic material model
-the boundaries of the body have been specified in the fluid solid interface boundary

I am currently using default values in the "initial values" and "prescribed mesh displacement" sections of the fsi module. Again, I am not sure if that is quite right.

The mesh is a fine free triangular mesh over the entire geometry. When I run the model over a chosen time dependent range I am continuously getting the following error

"Failed to evaluate variable Jacobian.
- Variable: mat.nu
- Geometry: 1
- Domain: 2"


I would greatly appreciate any help I can get. I have been working on this problem for the past few months without getting anywhere.

Thank you very much.