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.

Impacts of Circular Liquid Jet Injection Angle Into Low Subsonic Crossflow

2021 ◽  
Author(s):  
Si. Kasmaiee ◽  
M. Tadjfar ◽  
Sa. Kasmaiee
Keyword(s):  
High Speed ◽  
Flow Characteristics ◽  
Cross Flow ◽  
Liquid Jet ◽  
High Speed Photography ◽  
Interfacial Instabilities ◽  
Injection Angle ◽  
Circular Nozzle ◽  
Subsonic Crossflow ◽  
Working Liquid

Abstract One of the most common ways to obtain mixing between liquid and air, is by injecting the liquid jet into an incoming gaseous crossflow. The physics of this mixing flow is very complicated due to the presence of many flow interfacial instabilities. Usually, a perpendicular liquid jet into the cross flow airstream is used as the standard method of mixing. In the present work, the effect of the injection angle of the liquid flow emanated from a circular nozzle into airstream was experimentally investigated. The flow characteristics of the liquid jet were visualized by diffused backlight shadowgraph technique and high-speed photography. Water was used as the working liquid and tests were conducted into an incoming airstream at room temperature and pressure. A circular nozzle with 1.5 mm in diameter was used. The injection angles of the 30, 45, 60 and 90 degrees of the liquid jet into the airstream were considered. Different parameters of liquid jet flow such as breakup length and trajectory were measured. It was found that at low angles the path was independent from the momentum ratio.

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

Blunt Trailing Edge Shear Wake Development With Turbulent In-Flow Boundary Layers

2005 ◽  
Author(s):  
Dhanalakshmi Challa ◽  
Joe Klewicki
Keyword(s):  
Boundary Layer ◽  
Shear Layer ◽  
Boundary Layers ◽  
High Speed ◽  
Velocity Ratio ◽  
Free Shear Layer ◽  
Low Speed ◽  
Axial Pressure Gradient ◽  
Layer Flow ◽  
Good Agreement

Experiments are conducted to explore the structural mechanisms involved in the post-separation evolution of a wall-bounded to a free-shear turbulent flow. At the upstream, both the boundary layers are turbulent. Experiments were conducted in a two-stream shear-layer tunnel, under a zero axial pressure gradient shear-wake configuration. A velocity ratio near 2 was explored. Profile data were collected with a single wire probe at various locations downstream of the blunt separation lip. With this set of measurements, mean profile, axial intensity and measures of profile evolution indicate that the predominant shift from turbulent boundary layer to free shear-layer like behavior occurs between the downstream locations x/θ = 13.7 & 27.4, where θ is the upstream momentum deficit thickness on the low-speed stream. The shear wake width is observed to be nominally constant with the downstream position. Axial velocity spectra show that the transition from boundary layer flow to shear flow occurs earlier in high-speed stream when compared to low speed stream. Strouhal number, Sto, of initial vortex rollup based on initial momentum thickness was found to be 0.034, which is in very good agreement with the existing literature. Other measures are in good agreement with linear stability considerations found in the literature.

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

Computation of two-phase shear-layer flow using an Eulerian-Lagrangian analysis

1988 ◽  
Author(s):  
JAYANT SABNIS ◽  
SANG-KEUN CHOI ◽  
RICHARD BUGGELN ◽  
HOWARD GIBELING
Keyword(s):  
Shear Layer ◽  
Lagrangian Analysis ◽  
Two Phase ◽  
Layer Flow

scholarly journals Stability of a Viscous Liquid Jet in a Coaxial Twisting Compressible Airflow

Processes ◽  
2021 ◽  
Vol 9 (6) ◽  
pp. 918
Author(s):  
Li-Mei Guo ◽  
Ming Lü ◽  
Zhi Ning
Keyword(s):  
Viscous Liquid ◽  
Axial Velocity ◽  
Liquid Velocity ◽  
Velocity Ratio ◽  
Dominant Mode ◽  
Liquid Jet ◽  
Axisymmetric Mode ◽  
Jet Instability ◽  
Jet Stability ◽  
Jet Breakup

Based on the linear stability analysis, a mathematical model for the stability of a viscous liquid jet in a coaxial twisting compressible airflow has been developed. It takes into account the twist and compressibility of the surrounding airflow, the viscosity of the liquid jet, and the cavitation bubbles within the liquid jet. Then, the effects of aerodynamics caused by the gas–liquid velocity difference on the jet stability are analyzed. The results show that under the airflow ejecting effect, the jet instability decreases first and then increases with the increase of the airflow axial velocity. When the gas–liquid velocity ratio A = 1, the jet is the most stable. When the gas–liquid velocity ratio A > 2, this is meaningful for the jet breakup compared with A = 0 (no air axial velocity). When the surrounding airflow swirls, the airflow rotation strength E will change the jet dominant mode. E has a stabilizing effect on the liquid jet under the axisymmetric mode, while E is conducive to jet instability under the asymmetry mode. The maximum disturbance growth rate of the liquid jet also decreases first and then increases with the increase of E. The liquid jet is the most stable when E = 0.65, and the jet starts to become more easier to breakup when E = 0.8425 compared with E = 0 (no swirling air). When the surrounding airflow twists (air moves in both axial and circumferential directions), given the axial velocity to change the circumferential velocity of the surrounding airflow, it is not conducive to the jet breakup, regardless of the axisymmetric disturbance or asymmetry disturbance.

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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