Unstable Asymmetric Modes of a Liquid Jet

1999 ◽  
Vol 121 (2) ◽  
pp. 379-383 ◽  
Author(s):  
S. X. Shi ◽  
D. G. Xi ◽  
J. R. Qin ◽  
N. Liu ◽  
G. C. Shu
Keyword(s):  
High Speed ◽  
Three Dimensional ◽  
Linear Instability ◽  
Liquid Jet ◽  
Physical Conditions ◽  
Inviscid Gas ◽  
Theoretical Predictions ◽  
Linear Instability Analysis ◽  
Rates Of Growth ◽  
Gas Medium

This paper reports the results of a linear instability analysis for a viscous liquid jet injecting into a quiescent inviscid gas medium with three-dimensional disturbances. A dispersion equation that accounts for the growth of asymmetric waves is derived, and the maximum rates of growth of various modes are calculated. The asymmetric breakup phenomenon of the jet and its structures at different modes is also studied by using a high-speed multi-frame holographic system. The theoretical predictions agree well with the experimental observations. The results of this study thus confirm the existence and even domination of unstable asymmetric modes under certain physical conditions in the breakup process.

Linear Instability Analysis of an Annular Swirling Viscous Liquid Jet

2011 ◽  
Vol 66-68 ◽  
pp. 1556-1561 ◽  
Author(s):  
Kai Yan ◽  
Ming Lv ◽  
Zhi Ning ◽  
Yun Chao Song
Keyword(s):  
Viscous Liquid ◽  
Liquid Velocity ◽  
Aerodynamic Force ◽  
Numerical Procedure ◽  
Liquid Sheet ◽  
Linear Instability ◽  
Viscous Force ◽  
Liquid Jet ◽  
Instability Analysis ◽  
Linear Instability Analysis

A three-dimensional linear instability analysis was carried out for an annular swirling viscous liquid jet with solid vortex swirl velocity profile. An analytical form of dispersion relation was derived and then solved by a direct numerical procedure. A parametric study was performed to explore the instability mechanisms that affect the maximum spatial growth rate. It is observed that the liquid swirl enhances the breakup of liquid sheet. The surface tension stabilizes the jet in the low velocity regime. The aerodynamic force intensifies the developing of disturbance and makes the jet unstable. Liquid viscous force holds back the growing of disturbance and the makes the jet stable, especially in high liquid velocity regime.

Curved Non-Newtonian Liquid Jets With Surfactants

2009 ◽  
Vol 131 (9) ◽  
Author(s):  
Jamal Uddin ◽  
Stephen P. Decent
Keyword(s):  
Free Surface ◽  
Shear Thickening ◽  
Linear Instability ◽  
Liquid Jets ◽  
Liquid Jet ◽  
Long Wavelength ◽  
Droplet Sizes ◽  
Wavelength Approximation ◽  
Steady Solutions ◽  
Linear Instability Analysis

Applications of the breakup of a liquid jet into droplets are common in a variety of different industrial and engineering processes. One such process is industrial prilling, where small spherical pellets and beads are generated from the rupture of a liquid thread. In such a process, curved liquid jets produced by rotating a perforated cylindrical drum are utilized to control drop sizes and breakup lengths. In general, smaller droplets are observed as the rotation rate is increased. The addition of surfactants along the free surface of the liquid jet as it emerges from the orifice provides a possibility of further manipulating breakup lengths and droplet sizes. In this paper, we build on the work of Uddin et al. (2006, “The Instability of Shear Thinning and Shear Thickening Liquid Jets: Linear Theory,” ASME J. Fluids Eng., 128, pp. 968–975) and investigate the instability of a rotating liquid jet (having a power law rheology) with a layer of surfactants along its free surface. Using a long wavelength approximation we reduce the governing equations into a set of one-dimensional equations. We use an asymptotic theory to find steady solutions and then carry out a linear instability analysis on these solutions.

Three-dimensional flow structure and string cavitation in a fuel injector and their effects on discharged liquid jet

2019 ◽  
Vol 22 (1) ◽  
pp. 243-256 ◽  
Author(s):  
Rubby Prasetya ◽  
Akira Sou ◽  
Junichi Oki ◽  
Akira Nakashima ◽  
Keiya Nishida ◽  
...  
Keyword(s):  
Vortex Ring ◽  
Flow Structure ◽  
High Speed ◽  
Three Dimensional ◽  
Liquid Jet ◽  
Fuel Injector ◽  
High Speed Imaging ◽  
Three Dimensional Flow ◽  
Dimensional Flow ◽  
Stereo Particle Image Velocimetry

Two kinds of cavitation may occur in mini-sac type diesel injectors. The first is geometrical cavitation, which can usually be seen as a film-like structure in the nozzle. The second is the filament-like string cavitation. Both types of cavitation are known to affect fuel spray characteristics, although the effects of geometrical cavitation and that of string cavitation have not been individually clarified. Moreover, the mechanism behind string cavitation occurrence is still unclear. String cavitation usually occurs at low needle lift, which might indicate the existence of a vortex ring flow in the sac. However, because of the difficulty in precise flow measurement of the three-dimensional flow structure in the sac, the link between vortex ring flow and string cavitation occurrence in the sac has not been proven. In this study, high-speed imaging of string cavitation, geometrical cavitation, and discharged liquid jet of an enlarged three-hole mini-sac diesel fuel injector was conducted to individually clarify the effects of string cavitation and geometrical cavitation on the discharged liquid jet angle. Furthermore, tomographic–stereo particle image velocimetry was carried out on the sac. The experiments were conducted at two different needle lifts, to clarify the link between needle lifts and flow structure in the sac, as well as how it affects string cavitation occurrence and liquid jet angle. The results confirmed that at low needle lift, vortex ring flow forms in the sac, which may induce helical flow in the nozzle, resulting in a large jet angle. Vortex strength varies with time, and string cavitation occurs when the vortex is particularly strong. As a result, the magnitude of the jet angle increase at low needle lift is enhanced when string cavitation occurs. At high needle lift, flow pattern in the sac becomes relatively uniform, which makes it harder for string cavitation to form.

scholarly journals Laser-induced forward transfer of viscoplastic fluids

2019 ◽  
Vol 880 ◽  
pp. 497-513 ◽  
Author(s):  
Maziyar Jalaal ◽  
Martin Klein Schaarsberg ◽  
Claas-Willem Visser ◽  
Detlef Lohse
Keyword(s):  
High Speed ◽  
Laser Energy ◽  
Three Dimensional ◽  
Liquid Jet ◽  
Control Parameters ◽  
Optimal Conditions ◽  
High Speed Imaging ◽  
Three Dimensional Printing ◽  
Forward Transfer ◽  
Dimensional Printing

Laser-induced forward transfer (LIFT) is a nozzle-free printing technology that can be used for two- and three-dimensional printing. In LIFT, a laser pulse creates an impulse inside a thin film of material that results in the formation of a liquid jet. We experimentally study LIFT of viscoplastic materials by visualizing the process of jetting with high-speed imaging. The shape of the jet depends on the laser energy, focal height, surface tension and material rheology. We theoretically identify the characteristic jetting velocity and how it depends on the control parameters, and define non-dimensional groups to classify the regimes of jetting. Based on the results, we propose the optimal conditions for printing with LIFT technology.

Modal Analysis of Ballooning Strings With Small Sag

1999 ◽  
Author(s):  
Rongjun Fan ◽  
Sushil K. Singh ◽  
Christopher D. Rahn
Keyword(s):  
Steady State ◽  
High Speed ◽  
Natural Frequencies ◽  
Rotation Speed ◽  
Equations Of Motion ◽  
Three Dimensional ◽  
Mode Shapes ◽  
Theoretical Predictions ◽  
Nonlinear Equations Of Motion

Abstract During the manufacture and transport of textile products, yarns are rotated at high speed and form balloons. The dynamic response of the balloon to varying rotation speed, boundary excitation, and disturbance forces governs the quality of the associated process. Resonance, in particular, can cause large tension variations that reduce product quality and may cause yarn breakage. In this paper, the natural frequencies and mode shapes of a single loop balloon are calculated to predict resonance. The three dimensional nonlinear equations of motion are simplified via small steady state displacement (sag) and vibration assumptions. Axial vibration is assumed to propagate instantaneously or in a quasistatic manner. Galerkin’s method is used to calculate the mode shapes and natural frequencies of the linearized equations. Experimental measurements of the steady state balloon shape and the first two natural frequencies and mode shapes are compared with theoretical predictions.

A Quasi-Direct 3D Simulation of the Atomization of High-Speed Liquid Jets

2005 ◽  
Author(s):  
Gian Marco Bianchi ◽  
Piero Pelloni ◽  
Stefano Toninel ◽  
Ruben Scardovelli ◽  
Anthony Leboissetier ◽  
...  
Keyword(s):  
High Speed ◽  
Density Ratio ◽  
Three Dimensional ◽  
Liquid Jets ◽  
Liquid Jet ◽  
Nozzle Flow ◽  
Flow Conditions ◽  
Flow Perturbation ◽  
Spatially Correlated ◽  
Finite Volume Approach

In this paper a quasi-direct solution of transient three-dimensional CFD calculations based on a finite volume approach has been adopted to simulate the atomization process of high velocity liquid jets issuing an injector-like nozzle. An accurate Volume-of-Fluid (VOF) method is used to reconstruct and advect the interface between the liquid and gas phases. An extended mesh which includes the injector nozzle and the upstream plenum has been considered in order to investigate accurately the effect of nozzle flow conditions on the liquid jet atomization. Cavitation modeling has not been included in the present computations. Two different mean injection velocities, 150 m/s and 270 m/s, respectively, have been considered in the calculations as representative of semi-turbulent and fully-turbulent nozzle flow conditions. The liquid-to-gas density ratio is kept fixed at 57. The calculations show that atomisation is directly linked to the temporally and spatially correlated turbulence of the liquid jet. The bulk flow perturbation and the relaxation of the boundary layer have been found to be the basic mechanisms that generate surface perturbations of the liquid jet.

Three-Dimensional Linear Instability Analysis of Thermocapillary Return Flow on a Porous Plane

2010 ◽  
Vol 27 (2) ◽  
pp. 024707 ◽  
Author(s):  
Zhao Si-Cheng ◽  
Liu Qiu-Sheng ◽  
Nguyen-thi Henri ◽  
Billia Bernard
Keyword(s):  
Three Dimensional ◽  
Linear Instability ◽  
Return Flow ◽  
Instability Analysis ◽  
Linear Instability Analysis

Linear instability analysis of low- incompressible flow over a long rectangular finite-span open cavity

2016 ◽  
Vol 799 ◽  
Author(s):  
Qiong Liu ◽  
Francisco Gómez ◽  
Vassilios Theofilis
Keyword(s):  
Laminar Flow ◽  
Shear Layer ◽  
Three Dimensional ◽  
Linear Instability ◽  
Linear Amplification ◽  
Instability Analysis ◽  
Finite Span ◽  
Layer Mode ◽  
Linear Instability Analysis ◽  
Steady Laminar

TriGlobal linear instability analysis and direct numerical simulations have been performed to unravel the mechanisms ultimately responsible for transition of steady laminar flow over a long rectangular finite-span open cavity with dimensions $L$ : $D$ : $W$$=$ 6 : 1 : 2 to unsteadiness. The steady laminar three-dimensional flow loses stability at $\mathit{Re}_{D,cr}\approx 1080$ as a consequence of linear amplification of a travelling eigenmode that is qualitatively analogous to the shear-layer mode known from analyses of flow in spanwise-periodic cavities, but has a three-dimensional structure which is strongly influenced by the cavity lateral walls. Differences in the eigenspectrum of the present and the spanwise homogeneous flow configuration are documented. Topological changes exerted on the steady laminar flow by linear amplification of the unstable shear-layer mode are reminiscent of observations in experiments at an order of magnitude higher Reynolds number.

Modal Analysis of Ballooning Strings With Small Curvature

2000 ◽  
Vol 68 (2) ◽  
pp. 332-338 ◽  
Author(s):  
R. Fan ◽  
S. K. Singh ◽  
C. D. Rahn
Keyword(s):  
High Speed ◽  
Natural Frequencies ◽  
Equations Of Motion ◽  
Three Dimensional ◽  
Mode Shapes ◽  
Small Displacement ◽  
Axial Motion ◽  
Theoretical Predictions ◽  
Nonlinear Equations Of Motion

During the manufacture and transport of textile products, yarns are rotated at high speed. The surface of revolution generated by the rotating yarn is called a balloon. The dynamic response of the balloon to varying rotation speed, boundary excitation, and aerodynamic disturbances affects the quality of the associated textile product. Resonance, in particular, can cause large tension variations that reduce product quality and may cause yarn breakage. In this paper, the natural frequencies and mode shapes of a single loop balloon are calculated to predict resonance. The three-dimensional nonlinear equations of motion are simplified under assumptions of small displacement and quasi-static axial motion. After linearization, Galerkin’s method is used to calculate the mode shapes and natural frequencies. Experimental measurements of the steady-state balloon shape and the first two natural frequencies and mode shapes are compared with theoretical predictions.

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