FSI Module for blood vessel simulation

Hi,

I'm trying to implement a very basic 2D axisymmetric model of a blood vessel (straight tube) using the FSI module as I'm interested in getting a wall deformation profile. The problem is that my model always fails with the following error:

"Failed to find consistent initial values.
Segregated group 2

Attempt to evaluate real square root of negative number."

I have tried finer meshes and get the same error message. My suspicion is that the BC are not correct. For example I am unsure as to how I should define the Boundary Load on the FSI Boundary. At the inlet I would really only like to specify the pressure using the piecewise function that creates a pressure pulse.

Would someone with more experience with the FSI module be able to help me?

Thank you
Alexandra