Fluid at a constant flow rate passes through a long, straight, cylindrical pipe that has an axisymmetric convergent section at the end.
Which one of the following options correctly represents the velocity field in the converging section in cylindrical $(r, \theta, z)$ coordinates?
- Two-dimensional function of $r$ and $z$
- One-dimensional function of $r$
- Two-dimensional function of $r$ and $\theta$
- One-dimensional function of $z$
