Stability and contraction of a rectangular liquid metal jet in a vacuum environment

Hydrodynamic similarity criteria and experimental data are reported here from experiments underway at UCLA that simulate the slab jets of the HYLIFE-II inertial fusion reactor. The current experimental setup produces a 2×20 mm slab jet, and reaches a maximum Reynolds number 5×104, corresponding to a jet velocity of 12 m/s. A high-speed camera is used to obtain and analyze data. Two major phenomena are observed, the inversion (axis-switching) of the slab jet owing to surface tension and corner vortices; and surface waves due to turbulent velocity profile relaxation. The main purpose of this series of experiments is the study of the rapid inversion (almost 50% of the jet over the length of interest) seen in previous experiments. It is shown here that this was due to secondary flows caused by features of orifice nozzle design. Current experiments show an inversion length considerably in excess of analytic correlations based on 2-D inviscid theory. For parameters approaching HYLIFE-II jets, inversion length is shown to be more than several hundred non-dimensional lengths.