Effect of Weber Number on Disintegration of Liquid Sheet With Co-Flowing Gas

2014 ◽  
Author(s):  
Mohammad Ali ◽  
Mohammed S. Mayeed ◽  
A. K. M. Sadrul Islam ◽  
M. Quamrul Islam
Keyword(s):  
Weber Number ◽  
Gaseous Medium ◽  
Normal Force ◽  
Surface Force ◽  
Liquid Sheet ◽  
Navier Stokes ◽  
Stokes Systems ◽  
Sheet Breakup ◽  
Surface Tension Forces ◽  
Moving Liquid

The disturbances on the surface of a moving liquid sheet in a moving gaseous medium are studied to analyze the dynamics and breakup of the liquid sheet with co-flowing gas. The problem, composed of the Navier-Stokes systems associated with surface tension forces, is solved by the Volume of Fluid (VOF) technique with a Continuum Surface Force (CSF) manner artificially smoothing the discontinuity present at the interface. The investigation provides the insights into the dynamics and breakup processes. The inlet velocities of liquid and gas are determined by liquid and gas Weber number, respectively. It is found that the disturbances occurred by the gas Weber number controls the instability process for the liquid sheet breakup. The results show that there is a range of gas Weber number for the occurrence of droplet. In this range, the gas Weber number causes an aerodynamic normal force at the tip of the liquid sheet which is able to form a droplet from the tip of the liquid sheet. Below that range of gas Weber number, the aerodynamic normal force at the tip of the sheet is too low to produce a droplet and above the range, the aerodynamic normal force stretches the liquid sheet too much and no droplet occurs.

Dynamics of Liquid Sheet Breakup in Splash Plate Atomization

2017 ◽  
Vol 140 (1) ◽  
Author(s):  
G. Thunivumani ◽  
Hrishikesh Gadgil
Keyword(s):  
Solid Surface ◽  
Weber Number ◽  
Jet Impingement ◽  
Liquid Sheet ◽  
Force Balance ◽  
Impingement Angle ◽  
Wide Range ◽  
Perforated Sheet ◽  
Sheet Breakup ◽  
Regime Map

An experimental study was conducted to investigate the breakup of a liquid sheet produced by oblique impingement of a liquid jet on a plane solid surface. Experiments are carried out over a wide range of jet Weber number (80–6300) and various jet impingement angles (30 deg, 45 deg, and 60 deg) are employed to study the sheet dynamics. The breakup of a liquid sheet takes place in three modes, closed rim, open rim, and perforated sheet, depending upon the Weber number. The transitions across the modes are also influenced by the impingement angle with the transition Weber number reducing with increase in impingement angle. A modified regime map is proposed to illustrate the role of impingement angle in breakup transitions. A theoretical model based on force balance at the sheet edge is developed to predict the sheet parameters by taking the shear interaction between the sheet and the solid surface into account. The sheet shape predicted by the model fairly matches with the experimentally measured sheet shape. The breakup length and width of the sheet are measured and comparisons with the model predictions show good agreement in closed rim mode of breakup.

A non-linear model for impinging jets atomization

2008 ◽  
Vol 222 (2) ◽  
pp. 213-224 ◽  
Author(s):  
E A Ibrahim ◽  
B E Outland
Keyword(s):  
Linear Model ◽  
Weber Number ◽  
Drop Size ◽  
Impinging Jets ◽  
Liquid Sheet ◽  
Linear Perturbation ◽  
Breakup Length ◽  
Half Wavelength ◽  
Non Linear ◽  
Sheet Breakup

The problem considered is predicting the characteristics of the spray produced by atomization of an attenuating liquid sheet formed by the impingement of two liquid jets of equal diameters and momenta. A second-order non-linear perturbation analysis is employed to model the evolution of harmonic instability waves that lead to sheet distortion and fragmentation. The onset of atomization occurs when the uneven surface modulations of the thinning sheet bring its upper and lower interfaces in contact. It is found that the sheet is torn into ligaments at each half wavelength. The instability of the ligaments causes their eventual disintegration into drops. The results indicate that sheet breakup length, time, and resultant drop size decrease as Weber number is increased. A higher Weber number induces a greater sheet breakup thickness. The breakup length, thickness, time, and drop size are diminished at larger impingement angles. The theoretical predictions of the present non-linear model are in good agreement with available experimental data and empirical correlations for sheet breakup length and drop size.

Symmetric and Asymmetric Disturbances in the Rayleigh Zone of an Air-Assisted Liquid Sheet: Theoretical and Experimental Analysis

2020 ◽  
Vol 142 (7) ◽  
Author(s):  
V. Sivadas ◽  
S. Karthick ◽  
K. Balaji
Keyword(s):  
Growth Rate ◽  
Weber Number ◽  
High Speed ◽  
Low Frequency ◽  
Maximum Growth ◽  
Temporal Analysis ◽  
Average Frequency ◽  
Liquid Sheet ◽  
Number Ratio ◽  
Sheet Breakup

Abstract The temporal analysis of symmetric (dilatational) and asymmetric (sinusoidal) perturbations at the interface of a water sheet in a coflowing air stream focuses on low gas Weber number region (Weg < 0.4), namely, Rayleigh breakup zone. The motive for this investigation is to acquire a better insight of breakup phenomena involved, rather than technical relevance, by utilizing Kelvin–Helmholtz instability. Accordingly, perturbations are introduced on the basic flow whose stability is to be examined by the method of normal (Fourier) modes. The temporal growth-rate of perturbations is traced to extract the wavenumber associated with maximum growth-rate. Thus, the critical wavelength, in conjunction with the phase velocity of the disturbance will facilitate to obtain the corresponding breakup frequency of the liquid sheet. The analytical findings on liquid sheet breakup frequency with increasing Weber number ratio exhibit the dominance of symmetric wave over asymmetric wave. It also shows independent evolution of breakup frequency with respect to Weber number ratio for the respective perturbation modes, which appears to be a pointed profile. That is, the frequency contour for dilatational mode dips, whereas it rises for the sinusoidal mode and at the Weber number ratio of 0.518 the crossover occur. The theoretical results were substantiated by high-speed flow visualization studies that discern the coexistence of low-frequency (primary) and high-frequency (intermediate) breakup events. Furthermore, the empirical average frequency data track reasonably well with the dilatational instability.

scholarly journals Physics of Breakup in Liquid Column and Sheet

2011 ◽  
Vol 8 (2) ◽  
pp. 59
Author(s):  
M. Ali ◽  
M. Q. Islam ◽  
M. Khadem
Keyword(s):  
Surface Tension ◽  
Shear Force ◽  
Aerodynamic Force ◽  
Surface Tension Force ◽  
Liquid Sheet ◽  
Capillary Waves ◽  
Liquid Column ◽  
Capillary Instabilities ◽  
Sheet Breakup ◽  
Moving Liquid

 The details on breakup processes of liquid column and sheet are numerically investigated to provide the physics of the capillary instabilities and formation of liquid drops. Two cases are used: A numerical analysis on the capillary instabilities and breakup processes of a cylindrical liquid column and a moving liquid sheet in a moving gaseous medium to analyze the dynamics and breakup of the liquid sheet. The problem, composed of the Navier-Stokes systems associated with surface tension forces, is solved by the Volume of Fluid (VOF) technique with a Continuum Surface Force (CSF) to artificially smooth the discontinuity present at the interface. The results show that before disintegration of the liquid the capillary waves become unstable and the source of making the wave unstable is inherently developed by the system. The investigation of moving liquid sheet showed that the two modes of forces for liquid stretching exists: shear force causing the stretching of liquid by shear velocity and drag force causing the stretching of liquid by gas velocity ahead of the tip of the liquid sheets. Stretching of liquid by shear force causes the protrusion of liquid from the tip of liquid sheet and the surface tension force causes the tip of the sheet to make it round. It can also be revealed that the aerodynamic force at the tip of the sheet plays an important role to continue the stretching of sheet and controls the formation of droplet with the occurrence of sheet breakup. 

Numerical Study of Non-Newtonian Liquid Sheet Primary Breakup

2011 ◽  
Vol 130-134 ◽  
pp. 3628-3631
Author(s):  
L.P. He ◽  
Z.Y. Xia
Keyword(s):  
Free Surface ◽  
Stokes Equations ◽  
Numerical Study ◽  
Piecewise Linear ◽  
Surface Force ◽  
Liquid Sheet ◽  
Newtonian Liquid ◽  
Navier Stokes ◽  
Primary Breakup ◽  
Atomization Characteristics

Dynamic atomization processes of non-Newtonian liquid were investigated by the method of numerical simulation. The full transient process of the primary instability, deformation, and fragmentation of free surface were simulated numerically by solving the Navier-Stokes equations using an algorithm based on the finite volume method. The tracking of the free surface was achieved using the volume of fluid (VOF) technique and the geometric reconstruction was based on the technique of Piecewise-Linear Interface Construction (PLIC). The continuum surface force (CSF) method was used to model surface tension. In this paper, atomization characteristics of non-Newtonian liquid were analyzed detailedly. The distribution of dimensionless potential length against time was obtained, and the dimensionless wavelength of primary waves was investigated.

scholarly journals Dynamics of Single Droplet Splashing on Liquid Film by Coupling FVM with VOF

Processes ◽  
2021 ◽  
Vol 9 (5) ◽  
pp. 841
Author(s):  
Yuzhen Jin ◽  
Huang Zhou ◽  
Linhang Zhu ◽  
Zeqing Li
Keyword(s):  
Liquid Film ◽  
Weber Number ◽  
Stokes Equations ◽  
Numerical Study ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Single Droplet ◽  
Navier Stokes Equations ◽  
Volume Method ◽  
The Relationship

A three-dimensional numerical study of a single droplet splashing vertically on a liquid film is presented. The numerical method is based on the finite volume method (FVM) of Navier–Stokes equations coupled with the volume of fluid (VOF) method, and the adaptive local mesh refinement technology is adopted. It enables the liquid–gas interface to be tracked more accurately, and to be less computationally expensive. The relationship between the diameter of the free rim, the height of the crown with different numbers of collision Weber, and the thickness of the liquid film is explored. The results indicate that the crown height increases as the Weber number increases, and the diameter of the crown rim is inversely proportional to the collision Weber number. It can also be concluded that the dimensionless height of the crown decreases with the increase in the thickness of the dimensionless liquid film, which has little effect on the diameter of the crown rim during its growth.

Nonlinear instability of plane liquid sheets

2000 ◽  
Vol 406 ◽  
pp. 281-308 ◽  
Author(s):  
SEYED A. JAZAYERI ◽  
XIANGUO LI
Keyword(s):  
Weber Number ◽  
Density Ratio ◽  
Perturbation Expansion ◽  
Liquid Sheet ◽  
Fundamental Wave ◽  
Liquid Density ◽  
Initial Amplitude ◽  
Nonlinear Stability Analysis ◽  
Liquid Sheets ◽  
Breakup Time

A nonlinear stability analysis has been carried out for plane liquid sheets moving in a gas medium at rest by a perturbation expansion technique with the initial amplitude of the disturbance as the perturbation parameter. The first, second and third order governing equations have been derived along with appropriate initial and boundary conditions which describe the characteristics of the fundamental, and the first and second harmonics. The results indicate that for an initially sinusoidal sinuous surface disturbance, the thinning and subsequent breakup of the liquid sheet is due to nonlinear effects with the generation of higher harmonics as well as feedback into the fundamental. In particular, the first harmonic of the fundamental sinuous mode is varicose, which causes the eventual breakup of the liquid sheet at the half-wavelength interval of the fundamental wave. The breakup time (or length) of the liquid sheet is calculated, and the effect of the various flow parameters is investigated. It is found that the breakup time (or length) is reduced by an increase in the initial amplitude of disturbance, the Weber number and the gas-to-liquid density ratio, and it becomes asymptotically insensitive to the variations of the Weber number and the density ratio when their values become very large. It is also found that the breakup time (or length) is a very weak function of the wavenumber unless it is close to the cut-off wavenumbers.

Modeling of Gas Turbine Fuel Nozzle Spray

1997 ◽  
Vol 119 (1) ◽  
pp. 34-44 ◽  
Author(s):  
N. K. Rizk ◽  
J. S. Chin ◽  
M. K. Razdan
Keyword(s):  
Gas Turbine ◽  
Fuel Injection ◽  
Near Field ◽  
Continuous Phase ◽  
Liquid Sheet ◽  
Vapor Concentration ◽  
Fuel Vapor ◽  
Fuel Injector ◽  
Gas Temperature ◽  
Sheet Breakup

Satisfactory performance of the gas turbine combustor relies on the careful design of various components, particularly the fuel injector. It is, therefore, essential to establish a fundamental basis for fuel injection modeling that involves various atomization processes. A two-dimensional fuel injection model has been formulated to simulate the airflow within and downstream of the atomizer and address the formation and breakup of the liquid sheet formed at the atomizer exit. The sheet breakup under the effects of airblast, fuel pressure, or the combined atomization mode of the airassist type is considered in the calculation. The model accounts for secondary breakup of drops and the stochastic Lagrangian treatment of spray. The calculation of spray evaporation addresses both droplet heat-up and steady-state mechanisms, and fuel vapor concentration is based on the partial pressure concept. An enhanced evaporation model has been developed that accounts for multicomponent, finite mass diffusivity and conductivity effects, and addresses near-critical evaporation. The presents investigation involved predictions of flow and spray characteristics of two distinctively different fuel atomizers under both nonreacting and reacting conditions. The predictions of the continuous phase velocity components and the spray mean drop sizes agree well with the detailed measurements obtained for the two atomizers, which indicates the model accounts for key aspects of atomization. The model also provides insight into ligament formation and breakup at the atomizer exit and the initial drop sizes formed in the atomizer near field region where measurements are difficult to obtain. The calculations of the reacting spray show the fuel-rich region occupied most of the spray volume with two-peak radial gas temperature profiles. The results also provided local concentrations of unburned hydrocarbon (UHC) and carbon monoxide (CO) in atomizer flowfield, information that could support the effort to reduce emission levels of gas turbine combustors.

Longitudinal Aerodynamics of a Canard Guided Spin Stabilized Projectile

2012 ◽  
Vol 443-444 ◽  
pp. 719-723
Author(s):  
Xiu Ling Ji ◽  
Hai Peng Wang ◽  
Shi Ming Zeng ◽  
Chen Yang Jia
Keyword(s):  
Normal Force ◽  
Navier Stokes ◽  
Test Case ◽  
Aerodynamic Coefficients ◽  
Number Range ◽  
Detailed Understanding ◽  
Pitch Moment ◽  
Spinning Projectile ◽  
Mach 3 ◽  
Viable Approach

Navier–Stokes simulation is performed on a canard guided spinning projectile for different attack angles and circumferential position angles of canard over the Mach number range of 1.8–2.2. The computational Magnus moment coefficients of test case are validated with available experimental data of a Secant-Ogive-Cylinder-Boattail (SOCBT) configuration at Mach 3, demonstrating that the method can provide an accurate and viable approach for this problem. The aim of the present study is to provide a detailed understanding of the effects of canard with different circumferential position angles on longitudinal aerodynamic coefficients at three supersonic speeds and various angles of attack. And the results show that normal force coefficients and pitch moment coefficients vary periodically with the circumferential position angles of canard.

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