I'm trying to add a term representing a repulsion force at the translation velocity of the rhs vector. For this I have included two functions in the python layer for the fluid toolbox, fluid.cpp.

The first function contactForce computes the repulsion force and adds it to the rhs vector. And the second function linAssemblyPython allows to call the first function during solve.

As we use Navier-Stokes in the simulations, I implemented the same functions using residual: contactForceRes and ResAssemblyPython.

In the python script used to run the simulations, fluid-remesh.py, I thus added the line:
f.linAssemblyPython(f.contactForce)

In the linear case my program runs but I don't think that the contactForce function is actually called: no print and I still get the same results as for the simulations without the repulsion force, no matter how great the force is.

In the non-linear case with residual , I get the following error message:

Traceback (most recent call last):
  File "fluid-remesh.py", line 201, in <module>
    f.solve()
RuntimeError: make_tuple(): unable to convert arguments to Python object (compile in debug mode for details)

I tested the repulsion force computation, the implementation didn't have any problems at that level.