Oblique shock reflection from an axis of symmetry is studied using Whitham's theory
of geometrical shock dynamics, and the results are compared with previous numerical
simulations of the phenomenon by Hornung (2000). The shock shapes (for strong
and weak shocks), and the location of the shock-shock (for strong shocks), are in
good agreement with the numerical results, though the detail of the shock reflection
structure is, of course, not resolved by shock dynamics. A guess at a mathematical
form of the shock shape based on an analogy with the Guderley singularity in
cylindrical shock implosion, in the form of a generalized hyperbola, fits the shock
shape very well. The smooth variation of the exponent in this equation with initial
shock angle from the Guderley value at zero to 0.5 at 90° supports the analogy. Finally,
steady-flow shock reflection from a symmetry axis is related to the self-similar flow.