  The Reynolds number provides a characterization of the transition to
turbulent flow, with wide application in classical fluid dynamics. Identifying
such a parameter in superfluid systems is challenging due to their
fundamentally inviscid nature. Performing a systematic study of superfluid
cylinder wakes in two dimensions, we observe dynamical similarity of the
frequency of vortex shedding by a cylindrical obstacle. The universality of the
turbulent wake dynamics is revealed by expressing shedding frequencies in terms
of an appropriately defined superfluid Reynolds number, ${\rm Re}_s$, that
accounts for the breakdown of superfluid flow through quantum vortex shedding.
For large obstacles, the dimensionless shedding frequency exhibits a universal
form that is well-fitted by a classical empirical relation. In this regime the
transition to turbulence occurs at ${\rm Re}_s\approx 0.7$, irrespective of
obstacle width.
