Doubt regarding velocity components in cylindrical system
 

I am trying to simulate a Pressure swirl atomizer. The model is a 2D axisymmetric one. It has been meshed in GMSH and has been checked.

I am using interFoam solver for the same. The problem is that using the boundary conditions that i have specified the simulation runs without an error. But after a while the timestep goes to a very low value to compensate the maxCo.

I have a doubt regarding the kind of inlet velocity boundary condition that i am using. I think this is the source of all the problems.

1)I had used fixedValue and value uniform (a,b,c). Does a b c correspond to axial, radial and tangential component. If not how may i change it to cylindrical velocity components.
2) I used swirlInletVelocity with correct description of the three components. Yet the problem persists... Does that mean I am going about a wrong direction

I hope I have conveyed my doubt in an understandable manner. Looking forward to your help. And thanks in advance.