Influence of initial film radius and film thickness on the rupture of foam films

2021 ◽  
Vol 6 (1) ◽  
Author(s):  
Maulik S. Shah ◽  
Chris R. Kleijn ◽  
Michiel T. Kreutzer ◽  
Volkert van Steijn
Keyword(s):  
Film Thickness ◽  
Foam Films ◽  
Initial Film

Simulation of Multi-Mode Film Boiling Using Level Set Method

2009 ◽  
Author(s):  
Vinesh H. Gada ◽  
Atul Sharma
Keyword(s):  
Film Thickness ◽  
Level Set ◽  
Taylor Instability ◽  
Viscous Force ◽  
Film Boiling ◽  
Inertia Force ◽  
Initial Film ◽  
Wall Superheat ◽  
Rayleigh Taylor Instability ◽  
Multi Mode

2D transient multi-mode film boiling simulation of water near critical pressure (p = 0.99pc = 21.9 MPa) on a heated horizontal surface is carried out using an in-house Level Set (LS) method based semi-explicit finite volume method code. The influence of initial vapor film thickness (yo) on the dominant instability mode is evaluated by carrying out simulations on domain having width greater than most dangerous Taylor wavelength i.e. LX = 4λd with y0 = 0.0425λd and 0.125λd at low wall superheat (ΔT = 2K). For lower initial film thickness, the viscous force dominated Rayleigh-Taylor instability is captured and the average bubble spacing is found close to the prediction made using lubrication theory i.e. λP = 2λc = 0.816λd. However, for higher initial film thickness, the inertia force dominated Taylor-Helmholtz mode of instability is found with the average bubble spacing close to λd. Simulations are carried out to check the existence of Rayleigh-Taylor instability on various domain width LX = 2λd, 3λd, 4λd and 6λd at yo = 0.0425λd and ΔT = 2K. The average bubble spacing for all domain widths is found to be less than 2λc indicating that the Rayleigh-Taylor instability is dominant.

Foam Films Stabilized by Dodecyl Maltoside. 1. Film Thickness and Free Energy of Film Formation

Langmuir ◽  
2004 ◽  
Vol 20 (15) ◽  
pp. 6352-6358 ◽  
Author(s):  
RM. Muruganathan ◽  
R. Krustev ◽  
H.-J. Müller ◽  
H. Möhwald ◽  
B. Kolaric ◽  
...  
Keyword(s):  
Free Energy ◽  
Film Thickness ◽  
Film Formation ◽  
Foam Films ◽  
Dodecyl Maltoside

scholarly journals The Non-Unicity of the Film Thickness in the Hydrodynamic Lubrication: Novel Approach Generating Equivalent Micro-Grooves and Roughness

2021 ◽  
Vol 26 (3) ◽  
pp. 44-61
Author(s):  
M. El Gadari ◽  
M. Hajjam
Keyword(s):  
Film Thickness ◽  
Reynolds Equation ◽  
Pressure Field ◽  
Hydrodynamic Lubrication ◽  
Hydrodynamic Pressure ◽  
New Approach ◽  
Initial Film ◽  
Surface Finishes ◽  
Novel Approach ◽  
The 1960S

Abstract Since the 1960s, all studies have assumed that a film thickness “h” provides a unique pressure field “p” by resolving the Reynolds equation. However, it is relevant to investigate the film thickness unicity under a given hydrodynamic pressure within the inverse theory. This paper presents a new approach to deduce from an initial film thickness a widespread number of thicknesses providing the same hydrodynamic pressure under a specific condition of gradient pressure. For this purpose, three steps were presented: 1) computing the hydrodynamic pressure from an initial film thickness by resolving the Reynolds equation with Gümbel’s cavitation model, 2) using a new algorithm to generate a second film thickness, 3) comparing and validating the hydrodynamic pressure produced by both thicknesses with the modified Reynolds equation. Throughout three surface finishes: the macro-shaped, micro-textured, and rough surfaces, it has been demonstrated that under a specific hydrodynamic pressure gradient, several film thicknesses could generate the same pressure field with a slight difference by considering cavitation. Besides, this paper confirms also that with different ratios of the averaged film thickness to the root mean square (RMS) similar hydrodynamic pressure could be generated, thereby the deficiency of this ratio to define the lubrication regime as commonly known from Patir and Cheng theory.

scholarly journals Molecular Dynamics Simulation on Thin-Film Lubrication of a Mixture of Three Alkanes

Materials ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 3689
Author(s):  
Run Du ◽  
Anying Zhang ◽  
Zhihua Du ◽  
Xiaoyu Zhang
Keyword(s):  
Thin Film ◽  
Molecular Dynamics ◽  
Film Thickness ◽  
Md Simulation ◽  
Dynamics Simulation ◽  
Thin Film Lubrication ◽  
Thickness Change ◽  
Density Peaks ◽  
Initial Film ◽  
Film Lubrication

We used the COMPASS forcefield to perform molecular dynamics (MD) simulation of a mixture composed of three alkanes as the lubricant for the thin-film lubrication. The viscosity of the lubrication film in the non-working state, the final film thickness, and density distribution were investigated. The results reveal that the viscosity error among different initial film thicknesses in the non-working state is within 5%, which confirms the applicability of the model and the forcefield. The viscosity decreases oscillating as temperature increases. Whatever the initial film thickness is, the film thickness change rate with respect to pressure load is almost the same. When pressure increases, the density peaks increase. As the initial film thickness increases, the normalized thicknesses of adsorption and ordered layers decrease. In nanoscale, the density predicted by the MD simulation is higher than the prediction of the Tait equation, even if the adsorption layers is excluded.

Heat Transfer During Drop Impact Onto Wetted Heated Smooth and Structured Substrates: Experimental and Theoretical Study

2010 ◽  
Author(s):  
Tatiana Gambaryan-Roisman ◽  
Mete Budakli ◽  
Ilia V. Roisman ◽  
Peter Stephan
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Film Thickness ◽  
Spray Cooling ◽  
Drop Impact ◽  
Interface Temperature ◽  
Heated Plate ◽  
Initial Film ◽  
Impact Parameters ◽  
Heated Plates

Spray cooling is a very effective means of heat removal from hot surfaces. Its efficiency can be further improved using structured wall surfaces. One of the fundamental processes governing spray cooling is an impact of a single cold droplet onto a heated wetted wall. The hydrodynamics of drop impact governs the transient heat transport in the film and in the wall. We study hydrodynamics and heat transfer during impact of a single drop onto heated smooth and structured heated plates. The temperature distribution in the heated plates has been measured with seven thermocouples. The splash dynamics and the evolution of interface temperature distribution have been visualized using high-speed infrared thermography. The film thickness evolution in the inner region has been measured using chromatic confocal imaging technique. Initial film thickness and drop impact parameters have been varied in the experiments. The evolution of the temperature distribution at the liquid-gas interface and the instationary temperature distribution in the heated plate depend on the initial film thickness, impact parameters and the plate topography. A self-similar analytical solution of the full Navier-Stokes equations and of the energy equation is obtained for the velocity and temperature fields in the spreading film. The theory allows prediction of the contact temperature and the residual film thickness.

Model Study on the Oil Stiction of a Discharge Reed Valve in Compressors

2017 ◽  
Vol 140 (2) ◽  
Author(s):  
Fumitaka Yoshizumi ◽  
Yasuhiro Kondoh ◽  
Takahiro Moroi ◽  
Shinji Tamano ◽  
Yohei Morinishi
Keyword(s):  
Film Thickness ◽  
Simulation Model ◽  
Contact Area ◽  
Delay Time ◽  
Bubble Radius ◽  
Oil Viscosity ◽  
Cavitation Model ◽  
Oil Film ◽  
Initial Film ◽  
Reed Valve

In a discharge reed valve for compressors, the oil stiction by the oil film between the reed and the valve seat is investigated experimentally, and a simulation model is developed. Through a model experiment, the initial oil film thickness is measured by an interferometry method, and the valve displacement and the bore pressure are measured from the stiction to the valve opening. The opening delay time together with the initial oil film thickness is measured while changing the contact area and the oil species. In the simulation model, the deformation of the reed and the pressure of the oil film as a result of cavitation are coupled. In order to take into account the tensile stress in the oil film, a cavitation model directly simulating the expansion of cavitation bubbles is developed (herein, dynamic cavitation model). In the experiment, a smaller contact area, a larger initial film thickness, and a smaller oil viscosity yield a shorter delay. In the simulation, the dynamic cavitation model is advantageous in representing the experimental delay time. In particular, with respect to the relationship between the initial film thickness and the delay time, the dynamic cavitation model with an initial bubble radius that depends on the oil film thickness yields results similar to the experimental results.

A Hybrid Film Thickness Evaluation Scheme Based on Multi-Channel Interferometry and Contact Mechanics

1999 ◽  
Vol 122 (1) ◽  
pp. 16-22 ◽  
Author(s):  
J. Lord ◽  
A. Jolkin ◽  
R. Larsson ◽  
O. Marklund
Keyword(s):  
Refractive Index ◽  
Film Thickness ◽  
Contact Region ◽  
Thickness Measurement ◽  
Interesting Phenomenon ◽  
Thickness Profile ◽  
Thickness Determination ◽  
Evaluation Scheme ◽  
Initial Film ◽  
Correction Scheme

A hybrid evaluation scheme for EHL film thickness determination is proposed and discussed. The film thickness profile in the contact region is measured using interferograms produced with a novel multi channel interferometry method. Since the refractive index distribution in the contact is pressure-dependent, and the initial film thickness profile will be evaluated assuming atmospheric pressure, a refractive index correction scheme is employed. The correction scheme is based on the Lorenz-Lorentz equation and a pressure-density relation together with a numerical pressure solver taking the initial film thickness measurement as input. The film thickness determination scheme is applied to an interesting phenomenon that can be observed at sliding conditions when the discrepancy occurred in the form of a deep and large dimple in the conjunction. Such a dimple appeared instead of the conventional plateau. The phenomenon was studied under different degrees of sliding. The detailed film thickness maps and pressure distributions for highly loaded EHL conjunctions at high degrees of sliding are produced using a hybrid evaluation scheme. The results are analyzed and discussed. [S0742-4787(00)00301-5]

scholarly journals About the Inverse Theory and the Non-Unicity of the Film Thickness: Novel Approach Generating Equivalent Micro-Grooves and Roughness

2021 ◽  
Author(s):  
Mhammed ELGADARI ◽  
HAJJAM Mohamed
Keyword(s):  
Film Thickness ◽  
Reynolds Equation ◽  
Pressure Field ◽  
Hydrodynamic Pressure ◽  
Inverse Theory ◽  
New Approach ◽  
Initial Film ◽  
Surface Finishes ◽  
Novel Approach ◽  
The 1960S

Abstract Since the 1960s, all studies have assumed that a film thickness “h” provides a unique pressure field “p” by resolving the Reynolds equation. However, it is relevant to investigate the film thickness unicity under a given hydrodynamic pressure within the inverse theory. This paper presents a new approach to deduce from an initial film thickness a widespread number of thicknesses providing the same hydrodynamic pressure under a specific condition of gradient pressure. For this purpose, three steps were presented: 1) computing the hydrodynamic pressure from an initial film thickness by resolving the Reynolds equation with Gümbel’s cavitation model, 2) using a new algorithm to generate a second film thickness, 3) comparing and validating the hydrodynamic pressure produced by both thicknesses with the modified Reynolds equation. Throughout three surface finishes: the macro-shaped, micro-textured, and rough surfaces, it has been demonstrated that under a specific hydrodynamic pressure gradient, several film thicknesses could generate the same pressure field with a slight difference by considering cavitation. Besides, this paper confirms also that different ratios of the averaged film thickness by the root mean square (RMS) similar hydrodynamic pressure could be generated, thereby the deficiency of this ratio to define the lubrication regime as commonly known with Patir and Cheng theory.

Crystallization kinetics of water on graphite

2018 ◽  
Vol 20 (34) ◽  
pp. 21856-21863 ◽  
Author(s):  
Ryutaro Souda ◽  
Takashi Aizawa
Keyword(s):  
Film Thickness ◽  
Crystallization Kinetics ◽  
Deposition Temperature ◽  
Nucleation And Growth ◽  
Graphite Substrate ◽  
Initial Film ◽  
Kinetics Of

The nucleation and growth of water crystallites on a graphite substrate are discussed in terms of the initial film thickness, deposition temperature, and effects of adspecies.

Investigation on Process Dependence of Self-Assembled Metal Nanocrystals

2002 ◽  
Vol 737 ◽  
Author(s):  
Chungho Lee ◽  
Zengtao Liu ◽  
Edwin C. Kan
Keyword(s):  
Electron Microscope ◽  
Film Thickness ◽  
Process Parameters ◽  
Scanning Transmission Electron Microscope ◽  
Oxide Semiconductor ◽  
Mos Capacitors ◽  
Metal Nanocrystals ◽  
Initial Film ◽  
Nanocrystal Formation ◽  
Substrate Doping

ABSTRACTWe report the systematic characterization of metal nanocrystal formation on ultra-thin tunnel gate oxide (2∼3nm) for memory applications. To get a high density and small average size of nanocrystals, the process parameters including annealing temperature, initial film thickness, and substrate doping are investigated for Au, Ag, and Pt nanocrystal formation with Si nanocrystal structure as control samples. The observation of nanocrystal formation by scanning electron microscope (SEM) shows that annealing below melting temperature of deposited film contributes to the reshaping of nanocrystals, while the initial film thickness to actual nanocrystal growth. In addition, the Schottky charge effect from substrate doping is not negligible if the tunnel oxide is thin. Controlling the process parameters, Au, Ag, and Pt nanocrystals of 4.0×1011cm-2, 2.8×1011cm-2, and 2.4×1011cm-2 can be formed with mean size of 6.2nm, 6.6nm, and 8.0nm, respectively. The observation of nanocrystals by scanning transmission electron microscope (STEM) shows that nanocrystals are spherical and crystalline. Metal contamination to the Si/SiO2 interface is also closely monitored with many process recipes of metal nanocrystal formation on 2∼3nm oxide showing atomically clean interface. Electrical evaluation of nanocrystal formation is carried out by C-V measurements of metal-oxide-semiconductor (MOS) capacitors with embedded metal nanocrystals.

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