Wavelength and frequency of axis-switching phenomenon formed over rectangular and elliptical liquid jets

2019 ◽  
Vol 119 ◽  
pp. 144-154 ◽  
Author(s):  
A. Jaberi ◽  
M. Tadjfar
Keyword(s):  
Liquid Jets ◽  
Switching Phenomenon ◽  
Axis Switching

Comparative study on interfacial oscillations of rectangular and elliptical liquid jets

2020 ◽  
Vol 234 (7) ◽  
pp. 1272-1286 ◽  
Author(s):  
Amin Jaberi ◽  
Mehran Tadjfar
Keyword(s):  
Aspect Ratio ◽  
Weber Number ◽  
High Speed ◽  
Nozzle Geometry ◽  
Liquid Jets ◽  
High Speed Photography ◽  
Aspect Ratios ◽  
Water Jets ◽  
Switching Phenomenon ◽  
Axis Switching

The instability characteristics and flow structures of water jets injected from rectangular and elliptical nozzles with aspect ratios varying from 2 to 6 were experimentally studied and compared. Shadowgraph technique was employed for flow visualization, and structures on the liquid jet surface were captured using high speed photography. It was found that disturbances originating from the nozzle geometry initially perturbed the liquid column, and then, at high jet velocities, disturbances generated within the flow dominated the jet surface. It was also found that rectangular nozzles introduced more disturbances into the flow than the elliptical ones. The characteristic parameters of axis-switching phenomenon including wavelength, frequency, and amplitude were measured and compared. Axis-switching wavelength was found to increase linearly with Weber number. Also, the wavelengths of rectangular jets were longer than the elliptical jets. Further, the frequency of axis-switching was shown to be reduced with increase of both Weber number and aspect ratio. It was observed that the axis-switching amplitude increased monotonically, reached a peak, and then decreased gradually. It was also found that the axis-switching amplitude varied with Weber number. At lower values of Weber number, the rectangular nozzles had higher amplitude than the elliptical nozzles. However, at higher values of Weber number, this relation was reversed, and the elliptical nozzles had the higher axis-switching amplitudes. This reversal Weber number decreased with the orifice aspect ratio. The reversal Weber number for aspect ratio of 4 was about 289, and it had decreased to 144 for the aspect ratio of 6.

Numerical Simulation of Breakup of Elliptical Liquid Jet in Still Air

2012 ◽  
Author(s):  
Ehsan Farvardin ◽  
Ali Dolatabadi
Keyword(s):  
Numerical Simulation ◽  
Three Dimensional ◽  
Liquid Jets ◽  
Liquid Jet ◽  
Breakup Length ◽  
Aspect Ratios ◽  
Switching Phenomenon ◽  
Dimensional Simulation ◽  
Axis Switching ◽  
Recent Experimental Work

Numerical simulation of liquid jets ejecting from a set of elliptical jets with different aspect ratios between 1 (circular) to 3.85 is performed for several Weber numbers ranging 15 to 330. The axis-switching phenomenon and breakup length of the jets are characterized by means of a Volume of Fluid (VOF) method together with a dynamic mesh refinement model. This three dimensional simulation is compared with a recent experimental work and the results agree well. It is concluded that at Weber numbers less than 100, the breakup length of the liquid jet increases, reaches a peak and then decreases suddenly.

Numerical Simulation of the Breakup of Elliptical Liquid Jet in Still Air

2013 ◽  
Vol 135 (7) ◽  
Author(s):  
Ehsan Farvardin ◽  
Ali Dolatabadi
Keyword(s):  
Numerical Simulation ◽  
Three Dimensional ◽  
Liquid Jets ◽  
Liquid Jet ◽  
Breakup Length ◽  
Aspect Ratios ◽  
Switching Phenomenon ◽  
Dimensional Simulation ◽  
Axis Switching ◽  
Recent Experimental Work

The numerical simulation of liquid jets ejecting from a set of elliptical orifices with different aspect ratios between 1 (circular) and 3.85 is performed for several Weber numbers, ranging from 15 to 330. The axis-switching phenomenon and breakup length of the jets are characterized by means of a volume of fluid (VOF) method, together with a dynamic mesh refinement model. This three-dimensional simulation is compared with a recent experimental work and the results agree well. It is concluded that for Weber numbers ranging from 15 to 100, by increasing the Weber number, the breakup length of the liquid jet increases, reaches a peak, and then decreases suddenly.

Studies of magnetic axis switching phenomenon in magnetite

2007 ◽  
Vol 442 (1-2) ◽  
pp. 83-85 ◽  
Author(s):  
G. Król ◽  
J. Kusz ◽  
Z. Tarnawski ◽  
Z. Kąkol ◽  
A. Kozłowski ◽  
...  
Keyword(s):  
Magnetic Axis ◽  
Switching Phenomenon ◽  
Axis Switching

Axis-switching and breakup of rectangular liquid jets

2020 ◽  
Vol 126 ◽  
pp. 103242 ◽  
Author(s):  
Mohammad Reza Morad ◽  
Mahdi Nasiri ◽  
Ghobad Amini
Keyword(s):  
Liquid Jets ◽  
Axis Switching

Flow Characteristics of Water Jets Discharging From Rectangular and Elliptical Injectors

2018 ◽  
Author(s):  
Amin Jaberi ◽  
Mehran Tadjfar
Keyword(s):  
Weber Number ◽  
Flow Characteristics ◽  
Maximum Amplitude ◽  
Qualitative Description ◽  
Jet Flows ◽  
Reference Case ◽  
Cross Sectional ◽  
Water Jets ◽  
Switching Phenomenon ◽  
Axis Switching

The flow and breakup characteristics of water jets issuing from rectangular and elliptical injectors into still atmosphere were experimentally compared. Injectors were of the same cross-sectional area and a circular injector was also employed as the reference case. Digital images taken by a diffused backlight technique were processed to extract the main characteristics of the jet column at different jet velocities. The measurements were carried out for mass flow rates varying from 2 L/h to 120 L/h with small enough steps at low speeds to capture Rayleigh regime. Aside from the qualitative description of the jet flows, stability curve was plotted to make a comparison between different jets. The comparison revealed that the ellipse jet is the first one to reach the critical Weber number, while the circular jet remains laminar at higher velocities than the other two jets. Moreover, axis-switching phenomenon was carefully studied as the common characteristic of rectangular and elliptical jets. The wavelength and maximum amplitude of axis-switching were measured at different flow conditions and the results were compared. Though the axis-switching wavelength of both jets demonstrated a linear increment with Weber number, the rectangular jet was found to increase with a higher slope. Furthermore, the non-dimensional maximum amplitude of axis-switching showed an approximate behavior.

Entrance length effects on the flow features of rectangular liquid jets

2020 ◽  
pp. 095441002096844
Author(s):  
MH Aliyoldashi ◽  
M Tadjfar ◽  
A Jaberi
Keyword(s):  
Experimental Study ◽  
High Speed ◽  
Liquid Surface ◽  
Fluid Flows ◽  
Liquid Jets ◽  
High Speed Photography ◽  
Entrance Length ◽  
Flow Features ◽  
Flow Visualizations ◽  
Axis Switching

An experimental study was carried out to investigate the effects of entrance length on the main characteristics of rectangular liquid jets discharged into the stagnant atmosphere. Six rectangular nozzles, all with the same aspect ratio of 3 but with different entrance length ratios ranging from 3.3 to 60 were constructed. The physics of the fluid flows was visualized by the aid of backlight shadowgraph technique and high speed photography. Flow visualizations revealed that in the mid-range of Weber numbers, the perturbations induced over the liquid surface remarkably depended on the entrance length ratio. Moreover, the characteristics of the axis-switching instability of rectangular liquid jets were measured. It was found that axis-switching wavelength was independent of the entrance length, while the amplitude of axis-switching was directly influenced. For entrance length ratios smaller than 10, the amplitude was increased with increase of entrance length, whereas for entrance length ratios higher than 10, this trend was reversed. Measurements of breakup length also showed that the transition of flow regimes was not perceptibly affected by the entrance length.

Axis-Switching Behavior of Liquid Jets Issued from Non-Circular Nozzles Under Low-Intermediate Pressure

2021 ◽  
Vol 37 (2) ◽  
pp. 367-378
Author(s):  
Lin Hua ◽  
Hong Li ◽  
Yue Jiang
Keyword(s):  
Deformation Process ◽  
High Speed ◽  
Sprinkler Irrigation ◽  
High Speed Photography ◽  
Irrigation Systems ◽  
Intermediate Pressure ◽  
Water Jets ◽  
Switching Phenomenon ◽  
Circular Jets ◽  
Axis Switching

HighlightsThe flow behavior of water jets discharged from different orifices was investigated.High-speed photography (HSP) was used to obtain surface structures and spread characteristics of water jets.The deformation process in axis switching related to the corner vortices effect of non-circular jets was researched by numerical simulation.The axis switching of non-circular jets enhances entrainment ability of the jet.ABSTRACT. Low-intermediate pressure sprinkler irrigation systems are important research topics in the field of water-saving irrigation. Non-circular nozzles improve spray uniformity at lower pressures and are key components of sprinkler irrigation systems. In this article, the behavior of discharged water jets from nozzles with circular, square, and equilateral triangular orifices designed with the same flow rate was investigated. High-speed photography (HSP) was used to capture jet characteristics in the near field (z<20D). The largest spread angle was obtained for the square jet, which was on average 37% larger than that of the circular jet. In addition, numerical simulations were performed to analyze the axis-switching process using the large-eddy simulation (LES) method and the coupled level-set and volume of fluid (CLSVOF) method. The axis-switching phenomenon was observed in non-circular jets, in which surrounding air mixed with the jet and promoted the formation of thin diaphragm structures. The deformation process that occurs in axis switching is described according to the simulated vorticity and velocity fields. The research results suggest the axis-switching phenomenon is induced by corner vortex motions produced by the polygonal orifice, which accelerate the decay of the axial velocity and increase the jet entrainment rate. Thus, the effect of corner vortices should be considered in the design of polygonal nozzles. Keywords: Axis switching, High-speed photography, Liquid jet, Low-intermediate pressure sprinkler irrigation, Non-circular nozzle, Numerical simulation.

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