Free-Surface Shear Layer Instabilities on a High-Speed Liquid Jet

2000 ◽  
Vol 37 (1) ◽  
pp. 74-88 ◽  
Author(s):  
Kazuhiro Itoh ◽  
Yoshiyuki Tsuji ◽  
Hideo Nakamura ◽  
Yutaka Kukita
Keyword(s):  
Free Surface ◽  
Shear Layer ◽  
High Speed ◽  
Liquid Jet ◽  
Surface Shear

Prediction of free surface waves induced by shear layer instability on liquid jet

2004 ◽  
Vol 2004 (0) ◽  
pp. 209
Author(s):  
Masataka INOUE ◽  
Kazuhiro ITOH ◽  
Hiroshige KUMAMARU ◽  
Yutaka KUKITA
Keyword(s):  
Free Surface ◽  
Surface Waves ◽  
Shear Layer ◽  
Liquid Jet ◽  
Shear Layer Instability ◽  
Free Surface Waves

Study on Flow Fields of Boundary-Layer Separation and Hydraulic Jump during Rundown Motion of Shoaling Solitary Wave

2015 ◽  
Vol 09 (05) ◽  
pp. 1540002 ◽  
Author(s):  
Chang Lin ◽  
Ming-Jer Kao ◽  
Guang-Wei Tzeng ◽  
Wei-Ying Wong ◽  
James Yang ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Free Surface ◽  
Solitary Wave ◽  
Shear Layer ◽  
Flow Separation ◽  
Hydraulic Jump ◽  
High Speed ◽  
Flow Fields ◽  
Main Stream ◽  
Separated Shear Layer

The characteristics of flow fields for a complete evolution of the non-breaking solitary wave, having a wave-height to water-depth ratio of 0.363 and propagating over a 1:5 sloping bottom, are investigated experimentally. This study mainly focuses on the occurrences of both flow separation on the boundary layer under an adverse pressure gradient and subsequent hydraulic jump with the abrupt rising of free surface during rundown motion of the shoaling wave, together with emphasis on the evolution of vortex structures underlying the separated shear layer and hydraulic jump. A flow visualization technique with particle trajectory method and a high-speed particle image velocimetry (HSPIV) system with a high-speed digital camera were used. Based on the instantaneous flow images visualized and/or the ensemble-averaged velocity fields measured, the following interesting features, which are unknown up-to-date, are presented and discussed in this study: (1) Flow bifurcation occurring on both offshore and onshore sides of the explicit demarcation curve and the stagnation point during runup motion; (2) The dependence of the diffuser-like flow field, being changed from the supercritical flow in the shallower region to the subcritical flow in the deeper counterpart, on the Froude number during the early and middle stages of rundown motion; (3) The positions and times for the occurrences of the incipient flow separation and the sudden rising of free surface of the hydraulic jump; (4) The associated movement and evolution of vortex structures under the separated shear layer, the hydraulic jump and/or the high-speed external main stream of the retreated flow; and (5) The entrainment of air bubbles from the free surface into the external main stream of the retreated flow.

An Experimental Study of a Free-Surface Shear Layer With and Without the Presence of Surfactants

2002 ◽  
Author(s):  
Amy Wamcke Lang ◽  
Carlos E. Manglano
Keyword(s):  
Experimental Study ◽  
Surface Tension ◽  
Free Surface ◽  
Shear Layer ◽  
Turbulence Intensity ◽  
Shear Flows ◽  
Surface Shear ◽  
Surface Deformations

A free-surface shear layer was studied to ascertain the effects due to the presence of surface tension gradients on the directional shift of the shear layer and turbulence intensities in the vicinity of the water free-surface. It was found that the presence of surfactants altered the direction of the shear layer in the vicinity of the free surface, with the shear layer being pulled to the higher surface tension side. In addition, the turbulence intensity in the plane of the free surface was dramatically reduced, also leading to damped surface deformations. These results show conclusively that the role surfactants play in turbulent free-surface shear flows needs to be considered.

Model for the initiation of atomization in a high-speed laminar liquid jet

2014 ◽  
Vol 757 ◽  
pp. 665-700 ◽  
Author(s):  
Akira Umemura
Keyword(s):  
Shear Layer ◽  
Nozzle Exit ◽  
High Speed ◽  
Capillary Waves ◽  
Liquid Jet ◽  
Nozzle Wall ◽  
Jet Instability ◽  
Circular Nozzle ◽  
Layer Flow ◽  
Liquid Shear

AbstractA laminar water jet issuing at high speed from a short circular nozzle into air exhibits various instability features at different distances from the nozzle exit. Near the exit, the effects of gaseous friction and pressure are relatively weak. Deformation of the jet surface in this region is mainly due to the instability of a thin liquid shear layer flow, which relaxes from the velocity profile produced by the nozzle wall. In this paper, a model for this type of instability based on linear stability analysis is investigated to describe the process initiating the formation of liquid ligaments disintegrating into fine droplets near the nozzle exit. The modelling comprises identifying unstable waves excitable in the liquid shear layer and exploring a self-destabilizing mechanism by which unstable waves responsible for the formation of liquid ligaments are naturally reproduced from the upstream-propagating capillary waves produced by the growth of the unstable waves themselves. An expression for the location of ligament formation onset is derived that can be compared with experiments. The model also explains changes in jet instability features away from the nozzle exit and for very short nozzles.

scholarly journals A note on the impulse due to a vapour bubble near a boundary

1982 ◽  
Vol 23 (4) ◽  
pp. 383-393 ◽  
Author(s):  
J. R. Blake ◽  
P. Cerone
Keyword(s):  
Free Surface ◽  
Point Source ◽  
Cavitation Bubble ◽  
High Speed ◽  
Liquid Jet ◽  
Vapour Bubble ◽  
Rigid Boundary ◽  
Two Fluids ◽  
Collapse Phase

AbstractAn expression for the impluse due to a vapour (cavitation) bubble is obtained in terms of an integral over a nearby boundary. Examples for a point source near a free surface, rigid boundary, inertial boundary and a fluid of different density are considered. It appears that the sign of the impluse determines the direction a cavitation bubble will migrate and the direction of the high speed liquid jet during the collapse phase. The theory may explain recent observations on buoyant bubbles near an interface between two fluids of different densities.

NONLINEAR SIMULATION OF A HIGH-SPEED, VISCOUS LIQUID JET

1998 ◽  
Vol 8 (2) ◽  
pp. 155-178 ◽  
Author(s):  
J. H. Hilbing ◽  
Stephen D. Heister
Keyword(s):  
Viscous Liquid ◽  
High Speed ◽  
Liquid Jet ◽  
Nonlinear Simulation

Experimental Investigation of Boundary Layer Instabilities on the Free Surface of Non-Turbulent Jet

2012 ◽  
Author(s):  
Matthieu A. Andre ◽  
Philippe M. Bardet
Keyword(s):  
Boundary Layer ◽  
Free Surface ◽  
High Speed ◽  
Particle Tracking Velocimetry ◽  
Capillary Waves ◽  
Wave Growth ◽  
Image Velocimetry ◽  
Planar Laser ◽  
Surface Visualization ◽  
The Waves

Shear instabilities induced by the relaxation of laminar boundary layer at the free surface of a high speed liquid jet are investigated experimentally. Physical insights into these instabilities and the resulting capillary wave growth are gained by performing non-intrusive measurements of flow structure in the direct vicinity of the surface. The experimental results are a combination of surface visualization, planar laser induced fluorescence (PLIF), particle image velocimetry (PIV), and particle tracking velocimetry (PTV). They suggest that 2D spanwise vortices in the shear layer play a major role in these instabilities by triggering 2D waves on the free surface as predicted by linear stability analysis. These vortices, however, are found to travel at a different speed than the capillary waves they initially created resulting in interference with the waves and wave growth. A new experimental facility was built; it consists of a 20.3 × 146.mm rectangular water wall jet with Reynolds number based on channel depth between 3.13 × 104 to 1.65 × 105 and 115. to 264. based on boundary layer momentum thickness.

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