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

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.

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.

scholarly journals Studies of the Magnetic Axis Switching in Magnetite

2006 ◽  
Vol 109 (4-5) ◽  
pp. 601-605 ◽  
Author(s):  
G. Król ◽  
J. Kusz ◽  
Z. Tarnawski ◽  
Z. Kąkol ◽  
W. Tabiś ◽  
...  
Keyword(s):  
Magnetic Axis ◽  
Axis Switching

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.

Characteristics of a supersonic elliptic jet

2016 ◽  
Vol 120 (1225) ◽  
pp. 495-519 ◽  
Author(s):  
S.M. Aravindh Kumar ◽  
E. Rathakrishnan
Keyword(s):  
Near Field ◽  
Pressure Ratio ◽  
Major Axis ◽  
Pressure Gradients ◽  
Free Jet ◽  
Plane Normal ◽  
Switching Phenomenon ◽  
Pitot Pressure ◽  
Elliptical Jet ◽  
Axis Switching

ABSTRACTComparative mixing of a Mach 2 elliptical free jet from a convergent-divergent elliptic nozzle with an aspect ratio of 2:1 in the presence of adverse and marginally favourable pressure gradients has been studied experimentally. It is found that the mixing of the elliptical jet is higher than that for the equivalent circular jet at all the levels of expansion. The decay of elliptic jet is significantly higher than the equivalent circular jet in all three zones of the jet field – the core, characteristic decay and fully developed regions. The reason for the faster decay of the elliptic jet is found to be the continuous variation in the size of the mixing-promoting vortices shed from the nozzle exit owing to its azimuthal asymmetry. The evolution of the jet and its axis-switching phenomenon has been studied using iso-pitot pressure contours taken at different axial locations in the plane normal to the jet axis. As expected, the elliptic jet spreads faster along the minor axis plane than the major axis plane, leading to axis-switching at all the levels of expansion studied. The axis-switching of the elliptic jet shifts upstream with increase in nozzle pressure ratio (NPR) from 4 to 5; from 5 to 7, it shifts downstream. But at marginally under-expanded condition of NPR 8, the axis-switching is found to shift slightly upstream. The occurrence of axis-switching in the elliptic jet indicates enhanced near-field mixing, compared to the equivalent circular jet. The shadowgraph pictures of the jet reveal that the waves prevailing in the elliptic jet are significantly weaker than those in the circular jet.

Mixing and Combustion Characteristics of a Side Dump Combustor With Noncircular Fuel Injectors

1994 ◽  
Author(s):  
T. M. Liou ◽  
L. Chen
Keyword(s):  
Numerical Study ◽  
Three Dimensional ◽  
Reacting Flows ◽  
Combustion Characteristics ◽  
Combustion Model ◽  
Mean Velocity ◽  
Dump Combustor ◽  
Aspect Ratios ◽  
Switching Phenomenon ◽  
Axis Switching

A numerical study of the mixing and combustion characteristics of an axial jet issued from rectangular injectors of different aspect ratios (3 and 1/3) in a three-dimensional side-dump combustor is presented. The Reynolds number based on the bulk mean velocity and combustor duct height was 5.9×104 and the momentum ratio of the axial-fuel jet to the side-air jets was 0.2. A two equation k-ε turbulence model incorporating with a two-step finite-rate combustion model was adopted to simulate the nonreacting and reacting flows in a side-dump combustor. The computed nonreacting flow pattern was verified by the available experimental data. A comparison between the reacting and nonreacting flow patterns was made. The axis switching phenomenon previously observed for the unconfined or confined noncircular jets was examined in detail for the present side-dump combustor. It was found that the axis switching phenomenon was incomplete and that the aspect ratio had weak effects on the turbulent mixing and combustion in the ducted rocket combustor under the investigated conditions.

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.

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