scholarly journals Investigation of the mechanisms of sea spray generation induced by wind-wave interaction in laboratory conditions

2019 ◽  
Vol 213 ◽  
pp. 02036
Author(s):  
Alexander Kandaurov ◽  
Daniil Sergeev ◽  
Yuliya Troitskaya ◽  
Olga Ermakova
Keyword(s):  
High Speed ◽  
Wind Wave ◽  
Wave Interaction ◽  
Wave Crest ◽  
Applied Physics ◽  
Wave Flume ◽  
Wind Speeds ◽  
Laboratory Conditions ◽  
Academy Of Sciences

The paper presents the results of investigations of the mechanisms of spray of droplets generation within wind wave interaction obtained under laboratory conditions on the High-speed Wind-Wave Flume of the Institute of Applied Physics of the Russian Academy of Sciences. For the research, a multi-angle high-speed video system used together shadow method, including underwater illumination. The results allowed for the classification of mechanismsleading to the formation of droplets. Three main types of phenomena responsible for the generation of the spume droplets near the wave crest were specified: breakage of liquid ligaments, bursting of large submerged bubbles, and bag breakup. The last and less known mechanism claims to be dominant for high wind speeds and it was described in detail.

scholarly journals First air–sea gas exchange laboratory study at hurricane wind speeds

2013 ◽  
Vol 10 (6) ◽  
pp. 1971-1996
Author(s):  
K. E. Krall ◽  
B. Jähne
Keyword(s):  
Wave Breaking ◽  
High Speed ◽  
Wind Wave ◽  
Breaking Waves ◽  
Gas Transfer ◽  
Transfer Velocity ◽  
Wind Speeds ◽  
Hurricane Wind ◽  
Wide Range ◽  
Enhanced Surface

Abstract. In a pilot study conducted in October and November 2011, air–sea gas transfer velocities of the two sparingly soluble trace gases hexafluorobenzene and 1,4-difluorobenzene were measured in the unique High-Speed Wind-Wave Tank at Kyoto University, Japan. This air–sea interaction facility is capable of producing hurricane strength wind speeds of up to u10=67 m s−1. This constitutes the first lab study of gas transfer at such high wind speeds. The measured transfer velocities k600 spanned two orders of magnitude, lying between 11 cm h−1 and 1180 cm h−1 with the latter being the highest ever measured wind induced gas transfer velocity. The measured gas transfer velocities are in agreement with the only available dataset at hurricane wind speeds (McNeil and D'Asaro, 2007). The disproportionately large increase of the transfer velocities found at highest wind speeds indicates a new regime of air–sea gas transfer, which is characterized by strong wave breaking, enhanced turbulence and bubble cloud entrainment. It was found that tracers spanning a wide range of solubilities and diffusivities are needed to separate the effects of enhanced surface area and turbulence due to breaking waves from the effects of bubble and spray mediated gas transfer.

scholarly journals On the Interaction between Wind Stress and Waves: Wave Growth and Statistical Properties of Large Waves

2020 ◽  
Vol 50 (2) ◽  
pp. 383-397
Author(s):  
J. H. Lee ◽  
J. P. Monty
Keyword(s):  
Wind Speed ◽  
Wind Stress ◽  
Wave Interaction ◽  
Order Theory ◽  
Statistical Properties ◽  
Wave Crest ◽  
Strong Wind ◽  
Wave Growth ◽  
Wind Speeds ◽  
Local Wave

AbstractStatistical properties and development of wave fields with different wind forcings are investigated through parametric laboratory experiments. Thirty different, random sea states simulated using a JONSWAP spectrum are mechanically generated in deep-water conditions. Each of the random simulated sea states is exactly repeated but subjected to a range of different wind speeds to study the interaction between wind stress and the existing random sea state waves, especially the isolated effect of the wind stress on the largest waves. Wave crest distributions are sensitive to the wind at the extreme end such that there is an observed deviation from second-order theory for the largest (lowest probability) waves at high wind speed. Because the local wave steepness increases with wind speed, eventually reaching a breaking point, the growth of extreme waves (relative to the significant wave height) due to wind stress is shown to be limited by wave breaking. Even when large waves are breaking, the data reveal that amplitude modulation of wave groups is enhanced substantially as the wind speed increases due to the difference in growth rates between the highest and the lowest wave crests in a wave group. However, there is no evidence of an increase in modulation instability with the wind speed, suggesting that the wind–wave interaction under strong wind forcing dominates the wave growth mechanism over nonlinear wave interactions in a broadband wave field.

Wind-induced growth of water waves

1982 ◽  
Vol 123 ◽  
pp. 425-442 ◽  
Author(s):  
H. Mitsuyasu ◽  
T. Honda
Keyword(s):  
Growth Rate ◽  
Water Waves ◽  
Friction Velocity ◽  
Wind Wave ◽  
Wind Waves ◽  
Pure Water ◽  
Wave Flume ◽  
Wind Speeds ◽  
Wind Profiles ◽  
The Waves

Spatial growth of mechanically generated water waves under the action of wind has been measured in a laboratory wind-wave flume both for pure water and for water containing a surfactant (sodium lauryl sulphate, concentration 2.6 × 10−2%). I n the latter case, no wind waves develop on the surface of the mechanically generated waves as well as on the still water surface for wind speeds up to U10≈ 15 m/s, where U10 is the wind velocity at the height Z = 10 m. Therefore we can study the wind-induced growth of monochromatic waves without the effects of co-existing short wind waves. The mechanically generated waves grew exponentially under the action of the wind, with fetch in both cases. The measured growth rate β for the pure water can be fitted by β/f = 0.34(U*/C)2 0.1 [lsime ] U*/C [lsime ] 1.0, where f is the frequency of the waves, C is the corresponding phase velocity, and U, is the friction velocity obtained from vertical wind profiles. The effect of the wave steepness H/L on the dimensionless growth rate β/f is not clear, but seems to be small. For water containing the surfactant, the measured growth rate is smaller than that for pure water, but the friction velocity of the wind is also small, and the above relation between β/f and U*/C holds approximately if the measured friction velocity U* is used for the relation.

scholarly journals First laboratory study of air–sea gas exchange at hurricane wind speeds

Ocean Science ◽  
2014 ◽  
Vol 10 (2) ◽  
pp. 257-265 ◽  
Author(s):  
K. E. Krall ◽  
B. Jähne
Keyword(s):  
Wave Breaking ◽  
High Speed ◽  
Wind Wave ◽  
Gas Transfer ◽  
High Wind ◽  
Transfer Velocity ◽  
Data Set ◽  
Wind Speeds ◽  
Bubble Cloud ◽  
Hurricane Wind

Abstract. In a pilot study conducted in October and November 2011, air–sea gas transfer velocities of the two sparingly soluble trace gases hexafluorobenzene and 1,4-difluorobenzene were measured in the unique high-speed wind-wave tank at Kyoto University, Japan. This air–sea interaction facility is capable of producing hurricane strength wind speeds of up to u10 =67 m s−1. This constitutes the first lab study of gas transfer at such high wind speeds. The measured transfer velocities k600 spanned two orders of magnitude, lying between 11 cm h−1 and 1180 cm h−1 with the latter being the highest ever measured wind-induced gas transfer velocity. The measured gas transfer velocities are in agreement with the only available data set at hurricane wind speeds (McNeil and D'Asaro, 2007). The disproportionately large increase of the transfer velocities found at highest wind speeds indicates a new regime of air–sea gas transfer, which is characterized by strong wave breaking, enhanced turbulence and bubble cloud entrainment.

Experimental Study of Breaking Wave Impinging and Overtopping a Deck Structure

2016 ◽  
Author(s):  
Yun-Ta Wu ◽  
Kuang-An Chang
Keyword(s):  
High Speed ◽  
Bubbly Flow ◽  
Wave Interaction ◽  
Wave Structure ◽  
Breaking Waves ◽  
Breaking Wave ◽  
Floating Platform ◽  
Wave Flume ◽  
Image Velocimetry ◽  
Physical Insight

This paper presents an experimental work on a breaking wave impinging and overtopping a deck structure. Because the Particle Image Velocimetry (PIV) technique is known of unsuitable of applying in highly aerated flows such as breaking waves, a technology named Bubble Image Velocimetry (BIV) is adopted to quantify the turbulent velocity characteristics in the bubbly region. A high-speed camera is used to capture images during the wave-structure interaction event in the framework of BIV methodology and the images are subsequently processed using cross-correlation for velocity determination. A wave focusing method is employed to generate plunging breaker in a laboratory-scale wave flume, and the model structure is a horizontal, flat and rigid deck that can be considered as a representative of a coastal bridge or an offshore floating platform. The goal is to gain physical insight from the breaking wave interaction with a simplified structure through measuring the kinematics of the bubbly flow.

Rogue Waves in Wind Seas: An Experimental Model in an Annular Wind-Wave Flume

2017 ◽  
Author(s):  
A. Toffoli ◽  
D. Proment ◽  
H. Salman ◽  
J. Monbaliu ◽  
E. Stramignoni ◽  
...  
Keyword(s):  
Wave Field ◽  
Cross Sections ◽  
Wind Wave ◽  
Rogue Waves ◽  
Surface Elevation ◽  
Order Moment ◽  
Wave Flume ◽  
Wind Speeds ◽  
Resonant Wave ◽  
Development Regime

The probability of occurrence of rogue waves in wind-generated fields is investigated experimentally in an annular wind-wave flume. Unlike many experiments on rogue waves, where waves are mechanically generated, here the wave field is forced naturally by wind as it is in the ocean. The peculiar geometry of the flume makes waves propagating circularly in an unlimited-fetch condition. Water surface elevation was measured at specific cross-sections under the effect of different wind speeds to monitor the temporal evolution of the wave field. Results show that the kurtosis of the surface elevation, the fourth order moment of the probability density function and a measure of the percentage of extremes in a wave record, gradually increases in time with the evolution of the wave field. Deviations from Normal statistics are observed to be a function of wind speed. The maximum departure from Normality resembled the one induced by quasi-resonant wave-wave interactions and it is observed at the final stage of wave growth and immediately before reaching the fully development regime.

scholarly journals Investigation of the bag-breakup phenomena of the spray generation processes during wind-wave interaction in the laboratory experiments with optical methods

2021 ◽  
Vol 2127 (1) ◽  
pp. 012015
Author(s):  
A A Kandaurov ◽  
D A Sergeev ◽  
Yu I Troitskaya
Keyword(s):  
High Speed ◽  
Laboratory Experiments ◽  
Wind Wave ◽  
Wave Interaction ◽  
Optical Methods ◽  
Imaging Method ◽  
Thin Membrane ◽  
Spray Formation ◽  
High Speed Video ◽  
Shadow Imaging

Abstract Present paper devoted to the investigations with optical methods processes of artificially induced bag-breakup type of spray formation phenomenon within wind-wave interaction. Experiments were carried out on the Thermostratified Wind-Wave Tank of the IAP RAS. High-speed video filming with the shadow imaging method demonstrated that it was possible to artificially reproduce all the main stages of this phenomenon, which are also observed for the sporadically occurred ones: inflation of a thin membrane surrounded by a thicker rim, rupture of the membrane leading to the formation of small droplets, fragmentation of the rim with the formation of large droplets. Special processing of the images allowed us to estimate typical lifetimes and sizes of membrane for artificial bag-breakup events which turned out to be close to the same parameters for sporadically occurred ones.

Whitecap coverage measurements in laboratory modeling of wind-wave interaction in presence of induced wave breaking

2021 ◽  
Author(s):  
Alexander Kandaurov ◽  
Yuliya Troitskaya ◽  
Vasiliy Kazakov ◽  
Daniil Sergeev
Keyword(s):  
Wave Breaking ◽  
Water Surface ◽  
High Speed ◽  
Wind Wave ◽  
Wave Train ◽  
Side Wall ◽  
Channel Cross Section ◽  
Whitecap Coverage ◽  
Wave Channel ◽  
Manual Processing

<p>Whitecap coverage were retrieved from high-speed video recordings of the water surface obtained on the unique laboratory faculty The Large Thermostratified Test Tank with wind-wave channel (cross-section from 0.7×0.7 to 0.7×0.9 m<sup>2</sup> at the end, 12 m fetch, wind velocity up to 35 m/s, U<sub>10</sub> up to 65 m/s). The wind wave was induced using a wave generator installed at the beginning of the channel (a submerged horizontal plate, frequency 1.042 Hz, amplitude 93 mm) working in a pulsed operation (three periods). Wave breaking was induced in working area by a submerged plate (1.2×0.7 m<sup>2</sup>, up to 12 depth, AOA -11,7°). Experiments were carried out for equivalent wind velocities U<sub>10</sub> from 17.8 to 40.1 m/s. Wire wave gauge was used to control the shape and phase of the incident wave.</p><p>To obtain the surface area occupied by wave breaking, we used two Cygnet CY2MP-CL-SN cameras with 50 mm lenses. The cameras are installed above the channel at a height of 273 cm from the water surface, separated by 89 cm. The image scale was 302 μm/px, the size of the image obtained from each camera is 2048x1088 px<sup>2</sup>, which corresponds to 619x328 mm<sup>2</sup> (the long side of the frame along the channel). The shooting was carried out with a frequency of 50 Hz, an exposure time of 3 ms, 250 frames were recorded for each wave train. To illuminate the image areas to the side of the measurement area, a diffuse screen was placed on the side wall, which was illuminated by powerful LED lamps to create a uniform illumination source covering the entire side wall of the section.</p><p>Using specially developed software for automatic detection of areas of wave breaking, the values of the whitecap coverage area were obtained. Automatic image processing was performed using morphological analysis in combination with manual processing of part of the frames for tweaking the algorithm parameters: for each mode, manual processing of several frames was performed, based on the results of which automatic algorithm parameters were selected to ensure that the resulting whitecap coverage corresponded. Comparison of images obtained from different angles made it possible to detect and exclude areas of glare on the surface from the whitecap coverage.</p><p>The repeatability of the created wave breakings allows carrying out independent measurements for the same conditions, for example the parameters of spray generation will give estimations of the average number of fragmentation events per unit area of the wave breaking area.</p><p>The work was supported by the RFBR grants 21-55-50005 and 20-05-00322 (conducting an experiment), President grant for young scientists МК-5503.2021.1.5 (software development) and the RSF grant No. 19-17-00209 (data processing).</p>

Experimental Wave Flume Tests in ROV-Wave Interaction Effects on the Line Tension for a Work Class ROV in Splash Zone

2021 ◽  
Author(s):  
Michael Binsar Lubis ◽  
Mehrdad Kimiaei
Keyword(s):  
Time History ◽  
Wave Interaction ◽  
Line Tension ◽  
Irregular Waves ◽  
Splash Zone ◽  
Remotely Operated Vehicle ◽  
Wave Flume ◽  
Flume Tests ◽  
Tension Time ◽  
Work Class

Abstract Integrity and stability of Remotely Operated Vehicle (ROV) when passing through the splash zone is one of the main concerns in the design of an ROV-umbilical system. Due to the lightweight nature of ROV in water, the umbilical experiences repetitive rapid transitions between slack and taut as the ROV travels through the splash zone. These rapid transitions induce tension spikes in the umbilical, namely snap forces, that can endanger the launch and recovery of an ROV. Therefore, it is important to ensure that the tension spikes do not exceed the safe working load of the umbilical. In this study, launch and recovery of a deep-water work class ROV are experimentally investigated using a 1:10 scaled ROV model through a series of wave flume tests. Different regular and irregular waves are generated in the flume while the ROV model is hung over the flume in four different positions. The tension time-history in the line is measured and recorded using a load cell at the top-end of the line. A simplified numerical model for launch and recovery of the ROV is developed and the numerical results are compared with the experimental ones. It is shown that the presented simplified model can be accurately used for analysis of launch and recovery of the ROV.

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