Direct measurements of free surface smoothness in turbulent liquid sheets

The High-Yield Lithium-Injection Fusion Energy (HYLIFE)-II conceptual reactor design uses stationary and oscillating slab jets, or liquid sheets, of molten Flibe (Li2BeF4) to shield the chamber first walls from damaging neutrons, ions, and target debris. A lattice of stationary liquid sheets with the beams propagating through the lattice openings is used to protect chamber front and back walls. Extremely smooth sheets are required to effectively shield the chamber first walls without clipping the driver beams. Surface ripple and its growth are therefore a major concern in liquid protection design. In this study, a non-intrusive technique for directly visualizing and measuring the instantaneous free-surface geometry has been developed. Mean free-surface geometry and surface geometry fluctuation results for turbulent water sheets issuing vertically downwards into atmospheric pressure air are presented at Reynolds numbers based upon the nozzle thickness of 34000, at distances up to 25 nozzle thicknesses (25 delta) downstream of the nozzle exit.