  Dispersive shock waves (DSWs) of the defocusing radial nonlinear
Schr\"odinger (rNLS) equation in two spatial dimensions are studied. This
equation arises naturally in Bose-Einstein condensates, water waves and
nonlinear optics. A unified nonlinear WKB approach, equally applicable to
integrable or nonintegrable partial differential equations, is used to find the
rNLS Whitham modulation equation system in both physical and hydrodynamic type
variables. The description of DSWs obtained via Whitham theory is compared with
direct rNLS numerics; the results demonstrate very good quantitative agreement.
On the other hand, as expected, comparison with the corresponding DSW solutions
of the one-dimensional NLS equation exhibits significant qualitative and
quantitative differences.
