Development of supercritical motion and internal jumps within lock-release radial currents and draining flows

When released from rest in a cylindrical reservoir, relatively dense fluid flows radially and may drain freely over an edge or may propagate along the underlying boundary as a gravity current. Here we show that in both scenarios the unsteady fluid motions develop the same supercritical state, a phenomenon that does not occur in equivalent two-dimensional flows and which strongly influences the ensuing dynamics, even at long times after the release. In particular, we demonstrate the onset and persistence of supercritical outflow when fluid drains over an edge, and the development of internal bores within gravity current flow.