Formation process of a two-dimensional starting jet

• DOI: 10.1017/jfm.2025.3
• Publication Date: 2025-03-14T09:58:46Z
• Authors: Haojun Zheng; Lei Gao; Simon C.M. Yu

The formation process of a vortex pair generated by two-dimensional starting jet has been investigated numerically over range Reynolds numbers from 500 to 2000. effects stroke ratio and nozzle configuration are examined. Only single can be observed in the vorticity field small ratios less than 10 while leading formed larger eventually disconnects trailing jet. (13.6 9.3) for straight an orifice have identified circulation criterion they further analysed four other criteria. Using contraction coefficient, transformed into universal value at about 16.5 both nozzles. effect number on is found within 12 % parallel flow cases but it will increase up 27 non-parallel due shear-layer instability. A modified contraction-based slug model proposed, accurately predict total invariants (e.g. circulation, hydrodynamic impulse kinetic energy) shedding edge. Analytical estimation conducted matching predicted Pierrehumbert steady pairs. By assuming that pinch-off starts when achieves state, two analytical models proposed terms translational velocity. latter appears more appropriate flows.