# Vortex formation process in gravity-driven starting jets

Vortex formation process in gravity-driven starting jets Experiments were conducted to investigate the vortex formation process in gravity-driven starting jets at three Reynolds numbers ( $${Re = D\overline{W} _{0} /\nu = 2,358,}$$ 3,528 and 4,716, where D is the nozzle diameter, $${\overline{W} _{0}}$$ the average discharging velocity and ν the kinematic viscosity). Planar laser induced fluorescence (PLIF) was used to visualize the flow while particle image velocimetry (PIV) was used to quantify the 2D velocity and vorticity fields. Vortex leapfrogging was found to appear at Re = 2,358, while pinch-off for the leading vortex was observed in the other two cases. Conditions for the vortex pinch-off appeared to be different from those found in the piston-driven starting jets. Although the leading vortex attained the maximum circulation and energy level very quickly after the jet was initiated, its detachment from the main stem may not be achieved necessarily. Attempt had been made to elaborate the different flow characteristics for respective cases from the related distribution of circulation and energy level via the measured velocity field by PIV. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Experiments in Fluids Springer Journals

# Vortex formation process in gravity-driven starting jets

, Volume 42 (5) – Mar 29, 2007
15 pages

/lp/springer_journal/vortex-formation-process-in-gravity-driven-starting-jets-2mlq0NdI7a
Publisher
Springer-Verlag
Subject
Engineering; Engineering Fluid Dynamics; Fluid- and Aerodynamics; Engineering Thermodynamics, Heat and Mass Transfer
ISSN
0723-4864
eISSN
1432-1114
D.O.I.
10.1007/s00348-007-0290-6
Publisher site
See Article on Publisher Site

### Abstract

Experiments were conducted to investigate the vortex formation process in gravity-driven starting jets at three Reynolds numbers ( $${Re = D\overline{W} _{0} /\nu = 2,358,}$$ 3,528 and 4,716, where D is the nozzle diameter, $${\overline{W} _{0}}$$ the average discharging velocity and ν the kinematic viscosity). Planar laser induced fluorescence (PLIF) was used to visualize the flow while particle image velocimetry (PIV) was used to quantify the 2D velocity and vorticity fields. Vortex leapfrogging was found to appear at Re = 2,358, while pinch-off for the leading vortex was observed in the other two cases. Conditions for the vortex pinch-off appeared to be different from those found in the piston-driven starting jets. Although the leading vortex attained the maximum circulation and energy level very quickly after the jet was initiated, its detachment from the main stem may not be achieved necessarily. Attempt had been made to elaborate the different flow characteristics for respective cases from the related distribution of circulation and energy level via the measured velocity field by PIV.

### Journal

Experiments in FluidsSpringer Journals

Published: Mar 29, 2007

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