Faulty velocity vectors in Natural Circulation loop using BuoyantBoussinesqSimplefoam
 

I am trying to simulate a natural circulation loop in Openfoam-1.6 using buoyantBoussinesqSimpleFoam solver. I have created the geometry and meshing in gmsh.

The loop is a constant diameter pipe with a uniform flux boundary condition at the bottom (using fixedGradient) and a constant temperature condition at top. Rest of the loop is considered adiabatic wall.

After 100,000 iterations, the temperature seems fine (according to experimental data). But the velocity vectors seems to be leaking out of the geometry joints. What could be the possible error? Please help.