I am trying to solve a poiseuille flow example. I want to make use of the ls.scipy_iterative sovler. I am using the cg method. The problem definition file, mesh and the vtk output are attached. Also attached is a plot of the pressure and axial flow velocity along the axis of the pipe. As you can see, the solution is completely non-physical. The same case runs fine with the scipy_direct solver. What am I doing wrong?