scholarly journals Analysis of the effect of fish oil on wind waves and implications for air–water interaction studies

Ocean Science ◽  
2019 ◽  
Vol 15 (3) ◽  
pp. 725-743 ◽  
Author(s):  
Alvise Benetazzo ◽  
Luigi Cavaleri ◽  
Hongyu Ma ◽  
Shumin Jiang ◽  
Filippo Bergamasco ◽  
...  
Keyword(s):  
Fish Oil ◽  
Water Surface ◽  
Wind Waves ◽  
Surface Current ◽  
Capillary Waves ◽  
Long Waves ◽  
Clean Water ◽  
Oily Water ◽  
The One ◽  
Generation Of Wind Waves

Abstract. Surfactant layers with viscoelastic properties floating on the water surface dampen short gravity-capillary waves. Taking advantage of the known virtue of fish oil to still angry seas, a laboratory study has been made to analyse wind-wave generation and the interaction between wind waves, paddle waves, and airflow. This was done in a tank containing a thin fish-oil film uniformly spread on the water surface. The research was aimed, on the one hand, at quantifying for the first time the effectiveness of this surfactant at impeding the generation of wind waves and, on the other, at using the derived conditions to disentangle relevant mechanisms involved in the air–sea interaction. In particular, our main interest concerned the processes acting on the wind stress and on the wave growth. With oil on the water surface, we have found that in the wind-only condition (no paddle waves) the wave field does not grow from the rest condition. This equilibrium is altered by irregular paddle (long) waves, the generation and evolution of short waves (in clean water and with oil) being modified by their interaction with the orbital velocity of the long waves and their effect on the airflow. Paddle waves do grow under the action of wind, the amount being similar in clean and oily water conditions, a fact we ascribe to the similar distortion of the wind vertical profile in the two cases. We have also verified that the wind-supported stress on the oily water surface was able to generate a surface current, whose magnitude turns out to be comparable to the one in clean water. We stress the benefits of experiments with surfactants to explore in detail the physics at, and the exchanges across, the wavy and non-wavy air–water interface.

scholarly journals Fish oil in a wave tank: a look at the air-water response

2018 ◽  
Author(s):  
Alvise Benetazzo ◽  
Luigi Cavaleri ◽  
Hongyu Ma ◽  
Shumin Jiang ◽  
Filippo Bergamasco ◽  
...  
Keyword(s):  
Fish Oil ◽  
Water Surface ◽  
Wind Waves ◽  
Surface Current ◽  
Capillary Waves ◽  
Clean Water ◽  
Oily Water ◽  
Rest Condition ◽  
Water Response ◽  
The One

Abstract. Surfactant layers with viscoelastic properties floating on the water surface damp short gravity-capillary waves. Inspired by the known virtue of fish oil to still angry seas, a laboratory study has been made on wind wave generation and on the interaction between wind-waves, paddle-waves and airflow in a tank containing a thin fish oil film uniformly spread on the water surface. According to the Marangoni resonance-type damping mechanism, for oily surfaces the energy dissipation process is quite selective in wavenumbers, but its effects are not, since it spreads (although to a lesser extent) towards longer and shorter waves via nonlinear interactions and modification of the airflow profile. With a thin layer of oil on the surface, it is rather peculiar that in the wind-only condition (no paddle waves) the wave field does not grow from the rest condition. This equilibrium was altered by paddle (longer) waves, the generation and evolution of short waves (in clean water and with oil) being modified by their interaction with the orbital velocity of the longer waves and their effect on the airflow. Paddle waves did grow under the action of wind, how much being similar in clean and oily water conditions, a fact we ascribe to the similar distortion of the wind profile in the two cases. We have also found that wind-supported stress on the oily water surface was able to generate a surface current, whose magnitude turns out to be comparable to the one in clean water. Our results expand previous investigations on the same topic. We stress the benefit of experiments with surfactants to explore in detail the physics at, and the exchanges across, the wavy and no-wavy air-water interface.

Capillary–gravity and capillary waves generated in a wind wave tank: observations and theories

1995 ◽  
Vol 289 ◽  
pp. 51-82 ◽  
Author(s):  
Xin Zhang
Keyword(s):  
Power Law ◽  
Gravity Waves ◽  
Water Surface ◽  
Wind Wave ◽  
Wind Waves ◽  
Capillary Waves ◽  
Fourth Power ◽  
Two Dimensional ◽  
Short Waves ◽  
Surface Gradient

Short water surface waves generated by wind in a water tunnel have been measured by an optical technique that provides a synoptic picture of the water surface gradient over an area of water surface (Zhang & Cox 1994). These images of the surface gradient can be integrated to recover the shape of the water surface and find the two-dimensional wavenumber spectrum. Waveforms and two-dimensional structures of short wind waves have many interesting features: short and steep waves featuring sharp troughs and flat crests are very commonly seen and most of the short waves are far less steep than the limiting wave forms; waveforms that resemble capillary–gravity solitons are observed with a close match to the form theoretically predicted for potential flows (Longuet-Higgins 1989); capillaries are mainly found as parasitics on the downwind faces of gravity waves, and the longest wavelengths of those parasitic capillaries found are less than 1 cm; the phenomenon of capillary blockage (Phillips 1981) on dispersive freely travelling short waves is also observed. The spectra of short waves generated by low winds show a characteristic dip at the transition wavenumber between the gravity and capillary regimes, and the dip becomes filled in as the wind increases. The spectral cut-off at high wavenumbers shows a power law behaviour with an exponent of about minus four. The wavenumber of the transition from the dip to the cut-off is not sensitive to the change of wind speed. The minus fourth power law of the extreme capillary wind wave spectrum can be explained through a model of energy balances. The concept of an equilibrium spectrum is still useful. It is shown that the dip in the spectrum of capillary–gravity waves is a result of blockage of both capillary–gravity wind waves and parasitic capillary waves.

Generation of Wind Waves in Large Streams

2020 ◽  
Vol 24 (1) ◽  
pp. 518-525
Author(s):  
Eshev S.S.– DSc ◽  
I.X. Gayimnazarov ◽  
А.R. Rakhimov ◽  
Latipov Sh. A
Keyword(s):  
Wind Waves ◽  
Generation Of Wind Waves

Wave Buoy Performance in Short and Long Waves, Evaluated Using Tests on a Hexapod

2018 ◽  
Author(s):  
Sanne van Essen ◽  
Kevin Ewans ◽  
Jason McConochie
Keyword(s):  
Degrees Of Freedom ◽  
Wind Waves ◽  
Long Waves ◽  
Normal Operation ◽  
Period Range ◽  
Multiple Degrees Of Freedom ◽  
Hydrodynamic Response ◽  
Vertical Displacements ◽  
Internal Integration ◽  
Offshore Wave

Offshore wave conditions can be measured using wave buoys, which are generally designed for wind waves. Longer waves (swell or bound second-order waves) are very relevant for certain maritime structures. The accuracy of the instrumentation in a typical wave buoy in long and short waves was therefore studied, and it was investigated if the buoy can be applied in longer waves. A Waverider buoy was placed on a hexapod, which applied regular and irregular prescribed motions in multiple degrees of freedom. The hydrodynamic response of the buoy in waves and the effect of its mooring system were not evaluated; the buoy was assumed to follow the orbital motions of a wave and to rotate with its slope. The tests showed that the buoy sensors measure accelerations and rotations with periods between 1.5 and 35 s very well. Vertical displacements derived from the accelerations by the buoy are accurate for the period range of 2 to 20 s. In longer waves, the motions are significantly underestimated, even though the accelerations are accurately measured. This will not lead to large errors in normal operation, as the energy of such long waves is generally low. This explains why the buoy also performs well when it is subjected to irregular motions (less than 2% error in the significant wave height of a half-hour measurement in realistic irregular sea states with peak periods between 5 and 20 s can be expected). It can be concluded that the buoy accurately measures accelerations. The accuracy of the derived displacements decreases when very long swell wave energy (> 20 s) is present. Review of the internal integration procedure may be considered when there is a specific interest in measuring longer waves.

scholarly journals 4DVAR HF radar assimilation South of Africa

2020 ◽  
Author(s):  
Xavier Couvelard ◽  
Christophe Messager ◽  
Pierrick Penven ◽  
Phillipe Lattes
Keyword(s):  
Complex Dynamics ◽  
Surface Current ◽  
Hf Radar ◽  
Detailed Knowledge ◽  
Oceanic Circulation ◽  
Geostrophic Currents ◽  
Area Of Interest ◽  
Covered Area ◽  
The One ◽  
Gas Fields

Abstract The oceanic circulation south of Africa is characterized by a complex dynamics with a strong variability due to the presence of the Agulhas current and numerous eddies. The area of interest of this paper, is also the location of several natural gas fields under seafloor which are targeted for drilling and exploitation.The complex and powerful ocean currents induce significant issues for ship operations at the surface as well as under the surface for deep sea operations. Therefore, the knowledge of the state of the currents and the ability to forecast them in a realistic manner could greatly enforce the safety of various marine operation. Following this objective an array of HF radar systems was deployed to allow a detailed knowledge of the Agulhas currents and its associated eddy activity. It is shown in this study that 4DVAR assimilation of HF radar allow to represent the surface circulation more realistically. Two kind of experiments have been performed, a one-month analysis and two days forecast. The one-month 4DVAR experiment have been compared to geostrophic currents issued from altimeters and highlight an important improvement of the geostrophic currents. Furthermore, despite the restricted size of the area covered with HF radar, we show that the solution is improved almost in the whole domain, mainly upstream and downstream of the HF radar's covered area. We also show that while benefits of the assimilation on the surface current intensity is significantly reduced in the first 6 hours of the forecast, the correction in direction persists after 48 hours.

scholarly journals Efektivitas Saringan Abu Sekam Padi untuk Menurunkan Kekeruhan pada Air Sungai Martapura

2019 ◽  
Vol 15 (2) ◽  
pp. 647
Author(s):  
Syarifudin A. ◽  
Imam Santoso
Keyword(s):  
Drinking Water ◽  
River Water ◽  
Rice Husk ◽  
Rice Husk Ash ◽  
Preliminary Test ◽  
Quality Standard ◽  
Clean Water ◽  
Research Needs ◽  
The One ◽  
Number Of Bacteria

Abstract: The Effectiveness of Rice Husk Ash Filter to Reduce Turbidity of Martapura River Water. Martapura River water is used by people living on riverbanks for cooking, washing, bathing, and others. The main problem of Martapura river water is the turbidity which is relatively high so it needs to be processed first before use. The preliminary test conducted on August 15, 2016 shows the value of turbidity of Martapura river water at 38.9 NTU. This research was an experimental research with the one group pretest and posttest design which aimed to determine the effectiveness of the filter to reduce the turbidity of Martapura river water. The medium used was rice husk ash with variation of thickness were 13 cm, 26 cm, and 39 cm. The effectiveness of filtration was determined by comparing the turbidity of water filtered with standards. The turbidity of Martapura river water before filtered was 35.7 NTU. After filtered by 13 cm, 26 cm and 39 cm filter, the turbidity of water decreased consecutive to 2.97 NTU, 1.17 NTU, and 0.95 NTU, with decreasing percentages respectively of 91.7%, 96.7% and 97.3%. All filtered water showed turbidity fulfilled both the standar of clean water and drinking water so that rice husk ash filter was effective decreased turbidity of Martapura river water. Filtered water is recommended to be cooked first to boil when used for drinking water because the number of bacteria of Coli has not been studied. Further research needs to be conducted by adding other parameters according to water quality standard

Pilgrim Trust Lecture, Molecular layers

1939 ◽  
Vol 170 (940) ◽  
pp. 1-39 ◽  
Keyword(s):  
Surface Tension ◽  
Olive Oil ◽  
Water Surface ◽  
Organic Molecules ◽  
Critical Thickness ◽  
Clean Water ◽  
Oily Contamination ◽  
Molecular Layers ◽  
Modern Work

If fragments of camphor are placed upon a clean water surface they move about vigorously and may even be made to propel toy boats. The late Lord Rayleigh (1890 a, 1890 c) found that these movements stopped rather abruptly if the surface tension of the water was lowered by 21 dynes/cm. by oily contamination of the surface. The amount of olive oil needed for this purpose was surprisingly small, corresponding to a thickness of only 16 A (16 x 10 -8 cm.). Miss Pockels (1891) proved that any amount of olive oil less than enough to give a critical thickness of about 10 A had no effect whatever on the surface tension of water, but above this limit the surface tension decreased rapidly as the amount of oil was increased. Only 5 g. of olive oil would be needed to cover an acre of water surface with a film of this critical thickness. Miss Pockels also showed that accidental contamination of the surface, which had previously complicated nearly all observations of surface-tension phenomena, could be eliminated by using a trough filled to the brim with water, and sweeping impurities off the surface by the motion of barriers which rested on the edges of the trough. This use of movable barriers to confine films, to compress them or to remove them from the surface, laid the foundation for nearly all the modern work with films on water. The early theories of surface tension had been developed by physicists (Thomas Young 1805; Laplace, Gauss, etc.) who either treated liquids as continuous fluids between whose elements of volume forces acted, or considered only spherical molecules which exerted upon one another forces that varied as a function of the distance between molecular centres. Such theories naturally could not take into account the wealth of knowledge that had been accumulated by organic chemists regarding the structures of organic molecules.

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