scholarly journals Bubble production by air filament and cavity breakup in plunging breaking wave crests

2021 ◽  
Vol 929 ◽  
Author(s):  
Qiang Gao ◽  
Grant B. Deane ◽  
Lian Shen
Keyword(s):  
Surface Tension ◽  
Breaking Waves ◽  
Breaking Wave ◽  
Interface Instability ◽  
Interface Curvature ◽  
Rayleigh Taylor Instability ◽  
Air Cavities ◽  
Rayleigh Instabilities ◽  
Good Agreement

Air filaments and cavities in plunging breaking waves, generically cylinders, produce bubbles through an interface instability. The effects of gravity, surface tension and surface curvature on cylinder breakup are explored. A generalized dispersion relation is obtained that spans the Rayleigh–Taylor and Plateau–Rayleigh instabilities as cylinder radius varies. The analysis provides insight into the role of surface tension in the formation of bubbles from filaments and cavities. Small filaments break up into bubbles through a Plateau–Rayleigh instability driven through the action of surface tension. Large air cavities produce bubbles through a Rayleigh–Taylor instability driven by gravity and moderated by surface tension, which has a stabilizing effect. Surface tension, interface curvature and gravity are all important for cases between these two extremes. Predicted unstable mode wavenumber and bubble size show good agreement with direct numerical simulations of plunging breaking waves and air cylinders.

scholarly journals THE ROLE OF SURFACE TENSION IN BREAKING WAVES

1972 ◽  
Vol 1 (13) ◽  
pp. 22 ◽  
Author(s):  
Robert L. Miller
Keyword(s):  
Surface Tension ◽  
Natural Waters ◽  
Experimental Studies ◽  
Breaking Waves ◽  
Engineering Model ◽  
Constant Depth ◽  
Model Studies ◽  
Limit Form ◽  
Satisfactory Theory

Breaking criteria in the vicinity of the crest, such as limit crest angle and limit form, and larger dimensions such as limit height (H/L) and breaker height (Hb/db)» are found experimentally to be significantly affected by change in surface tension. A number of wave types were examined, including periodic waves, solitary waves, and standing waves, over both constant depth and uniform slopes. Variations in natural waters in some cases were found to be of equivalent magnitude to those induced for the experiments. The conclusion is drawn that surface tension should be taken into account in development of a satisfactory theory of breakers. It is also an important factor in experimental studies, particularly engineering model studies involving breaking waves.

scholarly journals NOISE CHARACTERISTICS OF SEA WAVES BASED ON ITS HEIGHT, PERIOD AND BREAKING WAVES

2020 ◽  
Vol 5 (2) ◽  
pp. 28-34
Author(s):  
Amron
Keyword(s):  
Pulse Duration ◽  
Breaking Waves ◽  
Breaking Wave ◽  
Interval Duration ◽  
Sea Waves ◽  
Noise Characteristics ◽  
Wave Parameters ◽  
Information And Communication ◽  
The Waves

ABSTRACT Wave sound is one of the sources of ambient noise in the waters which causes the role of sound as a transmission medium of information and communication becomes disrupted. The characteristics of wave noise can be influenced by their parameters, such as height and period of the waves and breaking waves. The study aimed to determine the characteristics of noise (intensity, frequency, pulse duration and interval duration) of waves based on its height, periods and breaking waves. Data acquisition for sound wave is obtained by hydrophones, visual of wave from CCTV cameras, and wave parameters is determined from ADCP data. Sound characteristics based its height, period and breaking waves were analyzed by Kruskal-Wallis analysis. The intensity of noise is affected by all wave parameters, while the pulse duration is significantly influenced by the changes in height and wave period, and the breaking waves velocity. Frequency of noise is only impacted by the breaking wave height. Other noise characteristics, the interval duration is not significantly influenced by all wave parameters.

The crushing of air cavities in a liquid

1992 ◽  
Vol 439 (1907) ◽  
pp. 611-626 ◽  
Keyword(s):  
Size Distribution ◽  
Breaking Waves ◽  
Breaking Wave ◽  
Size Distributions ◽  
Available Energy ◽  
Air Volume ◽  
Logarithmic Distribution ◽  
Bubble Sizes ◽  
Air Cavities ◽  
Satisfactory Theory

Although there is a growing amount of information on the distribution of bubble sizes in the upper layers of the ocean, no satisfactory theory for it has yet been given. In this paper we make a beginning with a theoretical model for the initial size distribution of bubbles generated by the shattering of a single air cavity, as in a breaking wave, when the bubbles are still close to the parent surface and before the distribution has been modified by buoyancy and convection. The expected size distribution depends upon the initial air volume and on the additional available energy. At small energies the probability density p ( a ) of bubble radii a is relatively narrow. At large energies the logarithmic distribution ap ( a ) tends to a certain unimodal form having a non-zero skewness. The width of the distribution at half its maximum is 2.16 octaves. Comparisons are made with both optical and acoustical measurements of the bubble size distributions from breaking waves in streams and in the ocean. A reasonable measure of agreement is found.

On the Role of Marangoni Effects on the Critical Heat Flux for Pool Boiling of Binary Mixtures

1996 ◽  
Vol 118 (1) ◽  
pp. 103-109 ◽  
Author(s):  
W. R. McGillis ◽  
V. P. Carey
Keyword(s):  
Surface Tension ◽  
Heat Flux ◽  
Binary Mixtures ◽  
Critical Heat Flux ◽  
Full Range ◽  
Pool Boiling ◽  
Marangoni Effect ◽  
Restoring Force ◽  
Marangoni Effects

The Marangoni effect on the critical heat flux (CHF) condition in pool boiling of binary mixtures has been identified and its effect has been quantitatively estimated with a modified model derived from hydrodynamics. The physical process of CHF in binary mixtures, and models used to describe it, are examined in the light of recent experimental evidence, accurate mixture properties, and phase equilibrium revealing a correlation to surface tension gradients and volatility. A correlation is developed from a heuristic model including the additional liquid restoring force caused by surface tension gradients. The CHF condition was determined experimentally for saturated methanol/water, 2-propanol/water, and ethylene glycol/water mixtures, over the full range of concentrations, and compared to the model. The evidence in this study demonstrates that in a mixture with large differences in surface tension, there is an additional hydrodynamic restoring force affecting the CHF condition.

scholarly journals Cavitation Bubble Cloud Break-Off Mechanisms at Micro-Channels

Fluids ◽  
2021 ◽  
Vol 6 (6) ◽  
pp. 215
Author(s):  
Paul McGinn ◽  
Daniel Pearce ◽  
Yannis Hardalupas ◽  
Alex Taylor ◽  
Konstantina Vogiatzaki
Keyword(s):  
Cavitation Bubble ◽  
Cavitation Inception ◽  
Wave Dynamics ◽  
Bubble Cloud ◽  
Cloud Dynamics ◽  
Micro Channels ◽  
Physical Insight ◽  
Cloud Process ◽  
Good Agreement

This paper provides new physical insight into the coupling between flow dynamics and cavitation bubble cloud behaviour at conditions relevant to both cavitation inception and the more complex phenomenon of flow “choking” using a multiphase compressible framework. Understanding the cavitation bubble cloud process and the parameters that determine its break-off frequency is important for control of phenomena such as structure vibration and erosion. Initially, the role of the pressure waves in the flow development is investigated. We highlight the differences between “physical” and “artificial” numerical waves by comparing cases with different boundary and differencing schemes. We analyse in detail the prediction of the coupling of flow and cavitation dynamics in a micro-channel 20 m high containing Diesel at pressure differences 7 MPa and 8.5 MPa, corresponding to cavitation inception and "choking" conditions respectively. The results have a very good agreement with experimental data and demonstrate that pressure wave dynamics, rather than the “re-entrant jet dynamics” suggested by previous studies, determine the characteristics of the bubble cloud dynamics under “choking” conditions.

scholarly journals Characteristics of Breaking Wave Forces on Piles over a Permeable Seabed

2021 ◽  
Vol 9 (5) ◽  
pp. 520
Author(s):  
Zhenyu Liu ◽  
Zhen Guo ◽  
Yuzhe Dou ◽  
Fanyu Zeng
Keyword(s):  
Wave Breaking ◽  
Stokes Equations ◽  
Slope Angle ◽  
Wave Force ◽  
Breaking Waves ◽  
Offshore Wind ◽  
Secondary Wave ◽  
Wave Forces ◽  
Breaking Wave ◽  
Breaking Wave Forces

Most offshore wind turbines are installed in shallow water and exposed to breaking waves. Previous numerical studies focusing on breaking wave forces generally ignored the seabed permeability. In this paper, a numerical model based on Volume-Averaged Reynolds Averaged Navier–Stokes equations (VARANS) is employed to reveal the process of a solitary wave interacting with a rigid pile over a permeable slope. Through applying the Forchheimer saturated drag equation, effects of seabed permeability on fluid motions are simulated. The reliability of the present model is verified by comparisons between experimentally obtained data and the numerical results. Further, 190 cases are simulated and the effects of different parameters on breaking wave forces on the pile are studied systematically. Results indicate that over a permeable seabed, the maximum breaking wave forces can occur not only when waves break just before the pile, but also when a “secondary wave wall” slams against the pile, after wave breaking. With the initial wave height increasing, breaking wave forces will increase, but the growth can decrease as the slope angle and permeability increase. For inclined piles around the wave breaking point, the maximum breaking wave force usually occurs with an inclination angle of α = −22.5° or 0°.

scholarly journals Theoretical Insight into the Reversal of Chemoselectivity in Diels-Alder Reactions of α,β-Unsaturated Aldehydes and Ketones Catalyzed by Brønsted and Lewis Acids

Organics ◽  
2021 ◽  
Vol 2 (1) ◽  
pp. 38-49
Author(s):  
Lakhdar Benhamed ◽  
Sidi Mohamed Mekelleche ◽  
Wafaa Benchouk
Keyword(s):  
Lewis Acids ◽  
Major Product ◽  
Diels Alder ◽  
Unsaturated Ketone ◽  
Unsaturated Aldehydes ◽  
Aldehydes And Ketones ◽  
Theoretical Insight ◽  
Insight Into ◽  
Good Agreement

Experimentally, a reversal of chemoselectivity has been observed in catalyzed Diels–Alder reactions of α,β-unsaturated aldehydes (e.g., (2E)-but-2-enal) and ketones (e.g., 2-hexen-4-one) with cyclopentadiene. Indeed, using the triflimidic Brønsted acid Tf2NH as catalyst, the reaction gave a Diels–Alder adduct derived from α,β-unsaturated ketone as a major product. On the other hand, the use of tris(pentafluorophenyl)borane B(C6F5)3 bulky Lewis acid as catalyst gave mainly the cycloadduct of α,β-unsaturated aldehyde as a major product. Our aim in the present work is to put in evidence the role of the catalyst in the reversal of the chemoselectivity of the catalyzed Diels–Alder reactions of (2E)-but-2-enal and 2-Hexen-4-one with cyclopentadiene. The calculations were performed at the ωB97XD/6-311G(d,p) level of theory and the solvent effects of dichloromethane were taken into account using the PCM solvation model. The obtained results are in good agreement with experimental outcomes.

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