Experimental and numerical study on the flapping motion of submerged turbulent plane jet

A submerged, vertical turbulent plane water jet impinging onto a free surface will be self-excited into a flapping oscillation when the jet velocity, leaving the jet orifice, exceeds a critical value. The flapping phenomenon was verified simultaneously in this paper by laser Doppler velocimeter measurement and numerical analyses with volume of fluid approach coupled with a large eddy simulation turbulent model. The general agreement of mean velocities between numerical predictions and experimental results in self-similar region is good for two cases: Reynolds numbers 2090 and 2970, which correspond to the stable impinging jet and flapping jet. Results show that the flapping jet is a new flow pattern for submerged turbulent plane jets with characteristic flapping frequency, and that the decay of the mean velocity along the jet centerline is considerably faster than that of the stable impinging state.