The mechanism of bubble detachment from a wall at zero and negative gravity

1976 ◽  
Vol 77 (2) ◽  
pp. 313-320 ◽  
Author(s):  
G. Malcotsis
Keyword(s):  
Surface Tension ◽  
Vertical Wall ◽  
Two Dimensions ◽  
Gravity Force ◽  
Zero Gravity ◽  
Air Bubbles ◽  
Subcooled Boiling ◽  
Vapour Bubble ◽  
Approximate Representation ◽  
Bubble Detachment

An experiment has been carried out in which air bubbles were caused to grow isothermally at a vertical wall between two closely spaced horizontal plates. The experiment gives an approximate representation in two dimensions for the growth of a vapour bubble at a wall under some conditions of subcooled boiling in zero gravity. Although the effect of gravity was virtually eliminated in the experiment, it was found that a bubble could still detach itself from the wall, apparently owing to the effects of surface tension and inertia.Also, bubbles were seen to detach from a wall despite the presence of a slight gravity force directed to oppose such detachment.

‘Effervescent’ atomization in two dimensions

2013 ◽  
Vol 714 ◽  
pp. 361-392 ◽  
Author(s):  
H. Lhuissier ◽  
E. Villermaux
Keyword(s):  
Nucleation Rate ◽  
Model Experiment ◽  
Drop Size ◽  
Surface Concentration ◽  
Two Dimensions ◽  
Air Bubbles ◽  
Two Dimensional ◽  
Atomization Process ◽  
Nucleation Sites ◽  
Size Dispersion

AbstractA planar Savart water sheet uniformly seeded with small air bubbles in a large surface concentration is studied as a model experiment of the so-called ‘effervescent’ atomization process. This two-dimensional setup allows for a quantitative observation of all the steps of the sheet’s disintegration into a collection of disjointed droplets. The bubbles are heterogeneous nucleation sites which puncture the sheet with holes. The dynamics of the opening of holes competes with the simultaneous nucleation rate of new holes in a statistically stationary fashion. The liquid constituting the sheet is then transiently concentrated in a web of ligaments of various lengths and diameters, at the junction between adjacent holes. Their breakup produces the final spray. We provide a complete description of the ligament web statistics when nucleation is synchronous, and we show that the drop size dispersion from the breakup of a single ligament is responsible for the shape of the overall spray drop size distribution.

Surface tension effects in the zero gravity inflow of a drop into a fluid

2000 ◽  
Vol 15 (2) ◽  
pp. 331-334 ◽  
Author(s):  
S. Residori ◽  
E. Pampaloni ◽  
P.K. Buah-Bassuah ◽  
F.T. Arecchi
Keyword(s):  
Surface Tension ◽  
Zero Gravity

On the Impedance of Statically-Balanced Mechanisms

2011 ◽  
Author(s):  
Qi Lu ◽  
Wenwu Xiu ◽  
Ou Ma
Keyword(s):  
Dynamic Effect ◽  
Gravity Force ◽  
Mechanical Resistance ◽  
Zero Gravity ◽  
Reduced Gravity ◽  
Simulation Fidelity ◽  
Input Motion ◽  
Optimal Set ◽  
Inertia Forces ◽  
Impedance Property

Statically-balanced technology is often used to compensate partial or full gravity force exerting on a mechanism in order to reduce the effort of driving the mechanism. Since such compensation is static, when a statically-balanced mechanism is used for dynamic applications, it will still have impedance (mechanical resistance to input motion) because the mechanism still subjects to the inertia forces although the gravity force has been compensated. Such a dynamic effect is undesirable for many applications, especially for those required to physically interact with humans and hence, the impedance property needs to be fully understood and possibly minimized in the design and/or operation of a statically-balanced mechanism. This paper studies the impedance property of passive statically-balanced mechanisms. Based on the study result, optimization strategies are proposed in order to optimize the operation of a statically-balanced mechanism. The strategies are then applied to a spring-based reduced-gravity simulation mechanism to figure out an optimal set of configurations in the workspace where the mechanism has the lowest impedance and the highest zero-gravity simulation fidelity.

scholarly journals Numerical study of surface tension effects on bubble detachment in a submerged needle

2015 ◽  
Author(s):  
J. Eshraghi ◽  
E. Kosari ◽  
P. Hadikhani ◽  
A. Amini ◽  
M. Ashjaee ◽  
...  
Keyword(s):  
Surface Tension ◽  
Numerical Study ◽  
Bubble Detachment

scholarly journals The Latest Method for Surface Tension Determination: Experimental Validation

Energies ◽  
2020 ◽  
Vol 13 (14) ◽  
pp. 3629
Author(s):  
Tomasz Janusz Teleszewski ◽  
Andrzej Gajewski
Keyword(s):  
Surface Tension ◽  
Heat Exchange ◽  
Closed Form ◽  
Laplace Equation ◽  
Experimental Validation ◽  
Reference Data ◽  
New Method ◽  
Air Bubbles ◽  
Inflection Points

The highest effectiveness of heat exchange is under boiling; hence, surface tension is an important parameter and should be determined when new liquid substances are created. The most popular methods are based on numerically solving the Young–Laplace equation by applying the Bashforth and Adams algorithm, which fails at the poles and at the inflection points. The newest algorithm is based on the closed-form expressions that define a drop or bubble. It gives the accurate solutions for the fully created drops or bubbles. To validate it, the surface tension value is determined for the air bubbles in water and compared with the reference data. Because the relative discrepancies are extremely small, the new method may be thought of as positively validated.

scholarly journals A Review on Bubble Stability in Fresh Concrete: Mechanisms and Main Factors

Materials ◽  
2020 ◽  
Vol 13 (8) ◽  
pp. 1820 ◽  
Author(s):  
Xiaohui Zeng ◽  
Xuli Lan ◽  
Huasheng Zhu ◽  
Haichuan Liu ◽  
Hussaini Abdullahi Umar ◽  
...  
Keyword(s):  
Surface Tension ◽  
Influencing Factors ◽  
Fresh Concrete ◽  
Foam Stability ◽  
Current Trend ◽  
Surface Elasticity ◽  
Air Bubbles ◽  
Huge Impact ◽  
The Stability ◽  
Air Liquid Interface

In order to improve the stability of air bubbles in fresh concrete, it is of great significance to have a better understanding of the mechanisms and main influencing factors of bubble stability. In the present review, the formation and collapse process of air bubbles in fresh concrete are essentially detailed; and the advances of major influencing factors of bubble stability are summarized. The results show that the surface tension of air–liquid interface exerts a huge impact on bubble stability by reducing surface free energy and Plateau drainage, as well as increasing the Gibbs surface elasticity. However, surface tension may not be the only determinant of bubble stability. Both the strength of bubble film and the diffusion rate of air through the membrane may also dominate bubble stability. The application of nano-silica is a current trend and plays a key role in ameliorating bubble stability. The foam stability could be increased by 6 times when the mass fraction of nano-particle reached 1.5%.

Effects of Gravity, Shear and Surface Tension in Internal Condensing Flows: Results From Direct Computational Simulations

2004 ◽  
Vol 126 (5) ◽  
pp. 676-686 ◽  
Author(s):  
Q. Liang ◽  
X. Wang ◽  
A. Narain
Keyword(s):  
Surface Tension ◽  
Normal Gravity ◽  
Numerical Solutions ◽  
Vertical Channel ◽  
Film Condensation ◽  
Vapor Flow ◽  
Zero Gravity ◽  
Pressure Drops ◽  
Condensing Flows ◽  
Internal Condensing Flows

The paper presents accurate numerical solutions of the full two-dimensional governing equations for steady and unsteady laminar/laminar internal condensing flows. The results relate to issues of better design and integration of condenser-sections in thermal management systems (looped heat pipes, etc.). The flow geometry, in normal or zero gravity, is chosen to be the inside of a channel with film condensation on one of the walls. In normal gravity, film condensation is on the bottom wall of a tilted (from vertical to horizontal) channel. It is found that it is important to know whether the exit conditions are constrained or unconstrained because nearly incompressible vapor flows occur only for exit conditions that are unconstrained. For the incompressible vapor flow situations, a method for computationally obtaining the requisite exit condition and associated stable steady/quasi-steady solutions is given here and the resulting solutions are shown to be in good agreement with some relevant experimental data for horizontal channels. These solutions are shown to be sensitive to the frequency and amplitude of the various Fourier components that represent the ever-present and minuscule transverse vibrations (standing waves) of the condensing surface. Compared to a vertical channel in normal gravity, shear driven zero gravity cases have much larger pressure drops, much slower wave speeds, much larger noise sensitive wave amplitudes that are controlled by surface tension, and narrower flow regime boundaries within which vapor flow can be considered incompressible. It is shown that significant enhancement in wave-energy and/or heat-transfer rates, if desired, are possible by designing the condensing surface noise to be in resonance with the intrinsic waves.

scholarly journals Reflection of water waves in the presence of surface tension by a nearly vertical porous wall

1998 ◽  
Vol 39 (3) ◽  
pp. 308-317 ◽  
Author(s):  
A. Chakrabarti ◽  
T. Sahoo
Keyword(s):  
Surface Tension ◽  
Water Waves ◽  
Vertical Wall ◽  
Porous Wall ◽  
Finite Depth ◽  
Regularity Property ◽  
Positive Real ◽  
First Order ◽  
The Subject ◽  
First Order Correction

AbstractIn the present paper the problem of reflection of water waves by a nearly vertical porous wall in the presence of surface tension has been investigated. A perturbational approach for the first-order correction has been employed as compared with the corresponding vertical wall problem. A mixed Fourier transform together with the regularity property of the transformed function along the positive real axis has been used to obtain the potential functions along with the reflection coefficients up to first order. Whilst the problem of water of infinite depth is the subject matter of the present paper, a similar approach is applicable to problems associated with water of finite depth.

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