Satellite formation during bubble transition through an interface between immiscible liquids

2014 ◽  
Vol 744 ◽  
Author(s):  
E. Q. Li ◽  
S. A. Al-Otaibi ◽  
I. U. Vakarelski ◽  
S. T. Thoroddsen
Keyword(s):  
Surface Tension ◽  
Time Scales ◽  
High Speed ◽  
Triple Line ◽  
Capillary Waves ◽  
Immiscible Liquids ◽  
Low Viscosity ◽  
Lower Viscosity ◽  
Power Law Exponent ◽  
Pass Through

AbstractWhen a bubble rises to an interface between two immiscible liquids, it can pass through the interface, if this is energetically favourable, i.e. the bubble preferring the side of the interface with the lower air–liquid surface tension. Once the intermediate film between the bubble and the interface has drained sufficiently, the bubble makes contact with the interface, forming a triple-line and producing strong capillary waves which travel around the bubble and can pinch off a satellite on the opposite side, akin to the dynamics in the coalescence cascade. We identify the critical Ohnesorge numbers where such satellites are produced and characterize their sizes. The total transition time scales with the bubble size and differential surface tension, while the satellite pinch-off time scales with the capillary-inertial time of the pool liquid, which originally surrounds the bubble. We also use high-speed video imaging to study the motion of the neck of the contact. For low viscosity we show that it grows in time with a power-law exponent between 0.44 and 0.50, with a prefactor modified by the net sum of the three interfacial tensions. Increasing the viscosity of the receiving liquid drop drastically slows down the motion of the triple-line, when the Ohnesorge number exceeds ${\sim }$0.08. This differs qualitatively from the coalescence of two miscible drops of different viscosities, where the lower viscosity sets the coalescence speed. We thereby propose a strong resistance from the triple-line.

Numerical computations of the dynamics of the disintegration of a drop situated in an electric field

1969 ◽  
Vol 312 (1509) ◽  
pp. 277-289 ◽  
Keyword(s):  
Surface Tension ◽  
Electric Field ◽  
Cross Sections ◽  
High Speed ◽  
Computer Time ◽  
Capillary Waves ◽  
Experimental Measurements ◽  
Pronounced Increase ◽  
Spheroidal Shape ◽  
Spheroidal Drop

The marker-and-cell technique, which has recently been developed for modelling the dynamics of incompressible fluid flow by means of a high-speed computer, has been applied to a study of the instability of an uncharged liquid drop of radius R and surface tension T situated in an electric field of strength E . This problem, which is of considerable importance in certain cloud physical situations, was previously treated analytically by Taylor who assumed that the drop retained a spheroidal shape throughout the period of deformation until the instability point was attained. His calculated instability criteria, namely that E(R/T) ½ = 1.625 when the ratio of the semi-major to semi-minor axes a/b = 1.9, agree well with experimental measurements. The present numerical calculations permit a quantitative assessment to be made of the validity of the spheroidal assumption and, of greater importance, provide a description of the dynamics of the disintegration of a drop subjected to intense electrical forces. In order to conserve computer time the initial condition was assumed to be that a spheroidal drop of undistorted radius 0.2 cm and surface tension 70 dyn cm –1 , possessing a degree of deformation represented by a/b = 1.9, was introduced into a field of strength E = 9500 V cm –1 , which is 4% greater than the critical value deduced on the basis of the spheroidal assumption. Computed cross-sections through the axis of the drop at appropriate intervals of time illustrate the onset of instability at the poles of the drop and demonstrate that the spheroidal assumption provides an extremely accurate representation of the shape of a drop situated in an electric field. This latter conclusion is reinforced by the calculated distribution of pressure over the surface of a spheroidal drop introduced into a critical field. Calculated values of the outward velocity of the fluid at the poles of the disintegrating drop show that capillary waves generated on the surface increase with amplitude until the final stage of instability is initiated, whereupon the velocity increases extremely rapidly, culminating in the ejection of fluid from each pole of the drop, probably in the form of a jet which subsequently breaks up to produce a number of droplets. The corresponding inward velocities at the equatorial points undergo much less variation than the polar velocity and do not exhibit a particularly pronounced increase at the time of instability. The computations indicate that the velocity of ejection of fluid from the poles of the drops is of the order of 100 cm s –1 . This value is in excellent agreement with experimental measurements made by several workers.

The Use of Styrenes as Embedding Media for Electron Microscopy

1971 ◽  
Vol 29 ◽  
pp. 488-489
Author(s):  
Edward D. De-Lamater ◽  
Eric Johnson ◽  
Thad Schoen ◽  
Cecil Whitaker
Keyword(s):  
Electron Microscopy ◽  
Surface Tension ◽  
Ultraviolet Light ◽  
Methyl Ethyl Ketone Peroxide ◽  
Methyl Ethyl ◽  
Styrene Polymerization ◽  
Radical Initiation ◽  
Tertiary Butyl ◽  
Low Viscosity ◽  
Free Radical Initiation

Monomeric styrenes are demonstrated as excellent embedding media for electron microscopy. Monomeric styrene has extremely low viscosity and low surface tension (less than 1) affording extremely rapid penetration into the specimen. Spurr's Medium based on ERL-4206 (J.Ultra. Research 26, 31-43, 1969) is viscous, requiring gradual infiltration with increasing concentrations. Styrenes are soluble in alcohol and acetone thus fitting well into the usual dehydration procedures. Infiltration with styrene may be done directly following complete dehydration without dilution.Monomeric styrenes are usually inhibited from polymerization by a catechol, in this case, tertiary butyl catechol. Styrene polymerization is activated by Methyl Ethyl Ketone peroxide, a liquid, and probably acts by overcoming the inhibition of the catechol, acting as a source of free radical initiation.Polymerization is carried out either by a temperature of 60°C. or under ultraviolet light with wave lengths of 3400-4000 Engstroms; polymerization stops on removal from the ultraviolet light or heat and is therefore controlled by the length of exposure.

scholarly journals Experimental investigation on spray characteristics of Jet A-1 and alternative aviation fuels

2021 ◽  
pp. 175682772110101
Author(s):  
Manish Kumar ◽  
Srinibas Karmakar ◽  
Sonu Kumar ◽  
Saptarshi Basu
Keyword(s):  
High Speed ◽  
Alternative Fuels ◽  
Droplet Formation ◽  
Spray Characteristics ◽  
Butyl Butyrate ◽  
Phase Doppler Interferometry ◽  
Alternative Aviation Fuels ◽  
Lower Viscosity ◽  
Fuel Jet ◽  
Atomization Characteristics

Potential alternative fuels that can mitigate environmental pollution from gas turbine engines (due to steep growth in the aviation sector globally) are getting significant attention. Spray behavior plays a significant role in influencing the combustion performance of such alternative fuels. In the present study, spray characteristics of Kerosene-based fuel (Jet A-1) and alternative aviation fuels such as butyl butyrate, butanol, and their blends with Jet A-1 are investigated using an air-blast atomizer under different atomizing air-to-fuel ratios. Phase Doppler Interferometry has been employed to obtain the droplet size and velocity distribution of various fuels. A high-speed shadowgraphy technique has also been adopted to make a comparison of ligament breakup characteristics and droplet formation of these alternative biofuels with that of Jet A-1. An effort is made to understand how the variation in fuel properties (mainly viscosity) influences atomization. Due to the higher viscosity of butanol, the SMD is higher, and the droplet formation seems to be delayed compared to Jet A-1. In contrast, the lower viscosity of butyl butyrate promotes faster droplet formation. The effects of the blending of these biofuels with Jet A-1 on atomization characteristics are also compared with that of Jet A-1.

scholarly journals Internal face finishing for a cooling channel using a fluid containing free abrasive grains

2021 ◽  
Author(s):  
Mitsugu Yamaguchi ◽  
Tatsuaki Furumoto ◽  
Shuuji Inagaki ◽  
Masao Tsuji ◽  
Yoshiki Ochiai ◽  
...  
Keyword(s):  
High Speed ◽  
Flow Behavior ◽  
Flow Simulation ◽  
Cooling Channel ◽  
H13 Steel ◽  
Channel Diameter ◽  
Abrasive Grains ◽  
Low Viscosity ◽  
Short Period ◽  
Internal Pressures

AbstractIn die-casting and injection molding, a conformal cooling channel is applied inside the dies and molds to reduce the cycle time. When the internal face of the channel is rough, both cooling performance and tool life are negatively affected. Many methods for finishing the internal face of such channels have been proposed. However, the effects of the channel diameter on the flow of a low-viscosity finishing media and its finishing characteristics for H13 steel have not yet been reported in the literature. This study addresses these deficiencies through the following: the fluid flow in a channel was computationally simulated; the flow behavior of abrasive grains was observed using a high-speed camera; and the internal face of the channel was finished using the flow of a fluid containing abrasive grains. The flow velocity of the fluid with the abrasive grains increases as the channel diameter decreases, and the velocity gradient is low throughout the channel. This enables reduction in the surface roughness for a short period and ensures uniform finishing in the central region of the channel; however, over polishing occurs owing to the centrifugal force generated in the entrance region, which causes the form accuracy of the channel to partially deteriorate. The outcomes of this study demonstrate that the observational finding for the finishing process is consistent with the flow simulation results. The flow simulation can be instrumental in designing channel diameters and internal pressures to ensure efficient and uniform finishing for such channels.

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.

Gliding Flight of the White-Backed Vulture Gyps Africanus

1971 ◽  
Vol 55 (1) ◽  
pp. 13-38 ◽  
Author(s):  
C. J. PENNYCUICK
Keyword(s):  
High Speed ◽  
Lift Coefficient ◽  
The Body ◽  
East African ◽  
Induced Drag ◽  
Gliding Flight ◽  
Vertical Speed ◽  
Statistical Sense ◽  
Pass Through ◽  
Comparison Measurements

1. Glide-comparison measurements were made on ten species of East African soaring birds using a Schleicher ASK-14 powered sailplane. Horizontal and vertical speed differences between bird and glider were measured by a photographic method, and used to estimate the bird's horizontal and vertical speeds relative to the air. The analysis refers to the white-backed vulture, since by far the largest number of measurements was obtained on this species. 2. A regression analysis using a two-term approximation to the glide polar yielded an implausibly high estimate of induced drag, which was attributed to a lack of observations at lift coefficients above 0.72. An amended glide polar was constructed assuming elliptical lift distribution and a maximum lift coefficient of 1.6 to define the low-speed end, while the high-speed end was made to pass through the mean horizontal and sinking speeds of all the experimental points. This curve gave a minimum sinking speed of 0.76 m/s at a forward speed of 10 m/s, and a best glide ratio of 15.3:1 at 13 m/s. It did not differ significantly (in the statistical sense) from the original regression curve. 3. In comparing the estimated circling performance, based on the amended glide polar, with that of the ASK-14, it was concluded that the rates of sink of both should be comparable, but that the glider would require thermals with radii about 4.3 times as great as those needed to sustain the birds. The conclusions are consistent with experience of soaring in company with birds. 4. In an attempt to assess the adaptive significance of the low-aspect-ratio wings of birds specializing in thermal soaring, the white-backed vulture's circling performance was compared with that of an ‘albatross-shaped vulture’, an imaginary creature having the same mass as a white-backed vulture, combined with the body proportions of a wandering albatross. It appears that the real white-back would be at an advantage when trying to remain airborne in thermals with radii between 14 and 17 m, but that the albatross-shaped vulture would climb faster in all wider thermals; on account of its much better maximum glide ratio, it should also achieve higher cross-country speeds. It is concluded that the wing shape seen in vultures and storks is not an adaptation to thermal soaring as such, but is more probably a compromise dictated by take-off and landing requirements. 5. The doubts recently expressed by Tucker & Parrott (1970) about the results and conclusions of Raspet (1950a, b; 1960) are re-inforced by the present experience.

Quantitative Analysis of Reynolds and Navier–Stokes Based Modeling Approaches for Isothermal Newtonian Elastohydrodynamic Lubrication

2021 ◽  
Vol 143 (12) ◽  
Author(s):  
Leoluca Scurria ◽  
Tommaso Tamarozzi ◽  
Oleg Voronkov ◽  
Dieter Fauconnier
Keyword(s):  
High Speed ◽  
Stokes Equations ◽  
Thickness Distribution ◽  
Elastohydrodynamic Lubrication ◽  
Lubricant Film ◽  
Secondary Flows ◽  
Navier Stokes ◽  
Shear Stresses ◽  
Low Viscosity ◽  
Fluid Film Thickness

Abstract When simulating elastohydrodynamic lubrication, two main approaches are usually followed to predict the pressure and fluid film thickness distribution throughout the contact. The conventional approach relies on the Reynolds equation to describe the thin lubricant film, which is coupled to a Boussinesq description of the linear elastic deformation of the solids. A more accurate, yet a time-consuming method is the use of computational fluid dynamics in which the Navier–Stokes equations describe the flow of the thin lubricant film, coupled to a finite element solver for the description of the local contact deformation. This investigation aims at assessing both methods for different lubrication conditions in different elastohydrodynamic lubrication (EHL) regimes and quantify their differences to understand advantages and limitations of both methods. This investigation shows how the results from both approaches deviate for three scenarios: (1) inertial contributions (Re > 1), i.e., thick films, high speed, and low viscosity; (2) high shear stresses leading to secondary flows; and (3) large deformations of the solids leading to inaccuracies of the Boussinesq equation.

The Aerodynamic Characteristics of the Pantograph When the Train Passes Through the Tunnel

2017 ◽  
Author(s):  
Dilong Guo ◽  
Wen Liu ◽  
Junhao Song ◽  
Ye Zhang ◽  
Guowei Yang
Keyword(s):  
High Speed ◽  
Aerodynamic Force ◽  
Maximum Amplitude ◽  
Aerodynamic Characteristics ◽  
High Speed Train ◽  
Expansion Waves ◽  
Compression And Expansion ◽  
High Speed Trains ◽  
Current Characteristics ◽  
Pass Through

The aerodynamic force acting on the pantograph by the airflow is obviously unsteady and has a certain vibration frequency and amplitude, while the high-speed train passes through the tunnel. In addition to the unsteady behavior in the open-air operation, the compressive and expansion waves in the tunnel will be generated due to the influence of the blocking ratio. The propagation of the compression and expansion waves in the tunnel will affect the pantograph pressure distribution and cause the pantograph stress state to change significantly, which affects the current characteristics of the pantograph. In this paper, the aerodynamic force of the pantograph is studied with the method of the IDDES combined with overset grid technique when high speed train passes through the tunnel. The results show that the aerodynamic force of the pantograph is subjected to violent oscillations when the pantograph passes through the tunnel, especially at the entrance of the tunnel, the exit of the tunnel and the expansion wave passing through the pantograph. The changes of the pantograph aerodynamic force can reach a maximum amplitude of 106%. When high-speed trains pass through tunnels at different speeds, the aerodynamic coefficients of the pantographs are roughly the same.

Excitation of standing gravity-capillary waves at an interface between two immiscible liquids by a periodic sequence of ultrasound pulses

2016 ◽  
Vol 24 (2) ◽  
pp. 155-160 ◽  
Author(s):  
A. P. Brysev ◽  
F. Zoueshtiagh ◽  
P. Pernod ◽  
V. L. Preobrazhensky ◽  
S. V. Diwakar ◽  
...  
Keyword(s):  
Capillary Waves ◽  
Periodic Sequence ◽  
Immiscible Liquids

scholarly journals Asymptotic Analysis of Nonlinear Resonance Interaction of Capillary Waves of Arbitrary Symmetry on Moving Charged Jet at Multimode Initial Deformation

2021 ◽  
Vol 57 (3) ◽  
pp. 72-82
Author(s):  
S. Shiryaeva ◽  
Keyword(s):  
Surface Tension ◽  
Nonlinear Resonance ◽  
Radial Electric Field ◽  
Resonant Interaction ◽  
Capillary Waves ◽  
Initial Deformation ◽  
Physical Parameters ◽  
Dimensionless Amplitude ◽  
Material Environment ◽  
The Waves

The problem of research of a nonlinear resonance between capillary waves on a surface of the charged jet at multimode initial deformation moving regarding the material environment is considered. It is shown in analytical asymptotic calculations of the second order on the dimensionless amplitude of oscillations that on a surface of a jet an internal nonlinear resonant interaction of capillary waves of any symmetry, both degenerate and secondary combinational, takes place. Positions of resonances depend on physical parameters of the system: the values of the coefficient of a surface tension and of the radial electric field at a surface of a jet, the velocity of its movement regarding the material environment, the values of the wave and azimuthal numbers of the interacting waves, a range of the waves defining initial deformation.

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