scholarly journals 3D Particle Tracking Velocimetry applied to droplets generated by breaking waves

2021 ◽  
Vol 1 (1) ◽  
Author(s):  
Reyna Guadalupe RAMIREZ DE LA TORRE ◽  
Atle Jensen
Keyword(s):  
Particle Tracking ◽  
Wave Breaking ◽  
Particle Tracking Velocimetry ◽  
Wave Train ◽  
Vertical Wall ◽  
Breaking Waves ◽  
Initial Distribution ◽  
Polar Regions ◽  
Droplet Sizes ◽  
The Impact

One of the environmental difficulties of exploring the polar regions is marine icing. The understanding of this phenomenon is important for the safety of installations, ships and people that operates in these environments. One of the main sources of marine icing is wave breaking. Therefore, experimental and field work has been conducted to understand the break-up of waves in different situations and some explanation have been proposed to the instabilities that create the spray formation. In this work, two different situations of wave breaking were studied: 1. Solitary waves were created and steepened by the use of a beach. The waves impacted on a vertical wall with different wall heights. 2. Violent plunging breakers were created by a focusing wave train and a sloping beach. The main objective of these experiments was to quantify the production of droplets from the impact by using Particle Tracking Velocimetry in 3 dimensions. It was found that the initial distribution of droplet sizes is similar in both experiments. These distributions are compared with previous studies, where the distribution of droplet sizes in different experimental cases were approximated by lognormal, Weibull or G-distributions respectively.

scholarly journals Suppression of Wind Ripples and Microwave Backscattering Due to Turbulence Generated by Breaking Surface Waves

2020 ◽  
Vol 12 (21) ◽  
pp. 3618
Author(s):  
Stanislav Ermakov ◽  
Vladimir Dobrokhotov ◽  
Irina Sergievskaya ◽  
Ivan Kapustin
Keyword(s):  
Remote Sensing ◽  
Surface Waves ◽  
Wave Breaking ◽  
Wave Train ◽  
Wind Waves ◽  
Breaking Waves ◽  
Doppler Spectrum ◽  
Strong Wave ◽  
Wave Maker ◽  
Radar Backscattering

The role of wave breaking in microwave backscattering from the sea surface is a problem of great importance for the development of theories and methods on ocean remote sensing, in particular for oil spill remote sensing. Recently it has been shown that microwave radar return is determined by both Bragg and non-Bragg (non-polarized) scattering mechanisms and some evidence has been given that the latter is associated with wave breaking, in particular, with strong breaking such as spilling or plunging. However, our understanding of mechanisms of the action of strong wave breaking on small-scale wind waves (ripples) and thus on the radar return is still insufficient. In this paper an effect of suppression of radar backscattering after strong wave breaking has been revealed experimentally and has been attributed to the wind ripple suppression due to turbulence generated by strong wave breaking. The experiments were carried out in a wind wave tank where a frequency modulated wave train of intense meter-decimeter-scale surface waves was generated by a mechanical wave maker. The wave train was compressed according to the gravity wave dispersion relation (“dispersive focusing”) into a short-wave packet at a given distance from the wave maker. Strong wave breaking with wave crest overturning (spilling) occurred for one or two highest waves in the packet. Short decimeter-centimeter-scale wind waves were generated at gentle winds, simultaneously with the long breaking waves. A Ka-band scatterometer was used to study microwave backscattering from the surface waves in the tank. The scatterometer looking at the area of wave breaking was mounted over the tank at a height of about 1 m above the mean water level, the incidence angle of the microwave radiation was about 50 degrees. It has been obtained that the radar return in the presence of short wind waves is characterized by the radar Doppler spectrum with a peak roughly centered in the vicinity of Bragg wave frequencies. The radar return was strongly enhanced in a wide frequency range of the radar Doppler spectrum when a packet of long breaking waves arrived at the area irradiated by the radar. After the passage of breaking waves, the radar return strongly dropped and then slowly recovered to the initial level. Measurements of velocities in the upper water layer have confirmed that the attenuation of radar backscattering after wave breaking is due to suppression of short wind waves by turbulence generated in the breaking zone. A physical analysis of the effect has been presented.

Extreme long waves over a varying bathymetry

2019 ◽  
Vol 878 ◽  
pp. 481-501 ◽  
Author(s):  
James G. Herterich ◽  
Frédéric Dias
Keyword(s):  
Conformal Mapping ◽  
Wave Breaking ◽  
Breaking Strength ◽  
Vertical Wall ◽  
Breaking Waves ◽  
Long Waves ◽  
Amplitude Wave ◽  
One Dimensional ◽  
Wave Interference ◽  
Initial Wave

Recent modelling work has shown that abrupt bathymetric transitions can produce dramatic amplifications of long waves, under the influence of both nonlinearity and dispersion. Here, the evolution of wave packets towards a vertical wall over a varying bathymetry is investigated with a one-dimensional conformal-mapping spectral code. In this system, wave breaking, runup and reflection, wave interference and bathymetric effects are highlighted. Wave breaking is examined with respect to geometric, kinematic and energetic conditions, with consistent results. The breaking strength is characterized for spilling and plunging based on initial wave period and amplitude. Non-breaking waves are amplified by reflection, interference and the bathymetry leading to large runups. In a typical example inspired by a real-world bathymetry, the maximum runup amplification approaches a factor of 12 – large enough for a 3 m amplitude wave to overtop a 30 m cliff.

scholarly journals Observations of Breaking Waves and Energy Dissipation in Modulated Wave Groups

2018 ◽  
Vol 48 (12) ◽  
pp. 2937-2948 ◽  
Author(s):  
David W. Wang ◽  
Hemantha W. Wijesekera
Keyword(s):  
Energy Dissipation ◽  
Wave Height ◽  
Wave Breaking ◽  
Dissipation Rate ◽  
Breaking Waves ◽  
Wave Groups ◽  
Dissipation Rates ◽  
Local Wave ◽  
Tke Dissipation Rate ◽  
The Impact

AbstractIt has been recognized that modulated wave groups trigger wave breaking and generate energy dissipation events on the ocean surface. Quantitative examination of wave-breaking events and associated turbulent kinetic energy (TKE) dissipation rates within a modulated wave group in the open ocean is not a trivial task. To address this challenging topic, a set of laboratory experiments was carried out in an outdoor facility, the Oil and Hazardous Material Simulated Environment Test Tank (203 m long, 20 m wide, 3.5 m deep). TKE dissipation rates at multiple depths were estimated directly while moving the sensor platform at a speed of about 0.53 m s−1 toward incoming wave groups generated by the wave maker. The largest TKE dissipation rates and significant whitecaps were found at or near the center of wave groups where steepening waves approached the geometric limit of waves. The TKE dissipation rate was O(10−2) W kg−1 during wave breaking, which is two to three orders of magnitude larger than before and after wave breaking. The enhanced TKE dissipation rate was limited to a layer of half the wave height in depth. Observations indicate that the impact of wave breaking was not significant at depths deeper than one wave height from the surface. The TKE dissipation rate of breaking waves within wave groups can be parameterized by local wave phase speed with a proportionality breaking strength coefficient dependent on local steepness. The characterization of energy dissipation in wave groups from local wave properties will enable a better determination of near-surface TKE dissipation of breaking waves.

scholarly journals Wave Peel Tracking: A New Approach for Assessing Surf Amenity and Analysis of Breaking Waves

2021 ◽  
Vol 13 (17) ◽  
pp. 3372
Author(s):  
Michael Thompson ◽  
Ivan Zelich ◽  
Evan Watterson ◽  
Tom E. Baldock
Keyword(s):  
Wave Breaking ◽  
Objective Assessment ◽  
Breaking Waves ◽  
Assessment Method ◽  
Coastal Development ◽  
Gold Coast ◽  
New Wave ◽  
New Approach ◽  
Automated Method ◽  
The Impact

The creation and protection of surfing breaks along populated coastlines have become a consideration for many councils and governments as surfing breaks are a major driver of tourism. To assess the surf amenity of surfing breaks, a quantitative and objective assessment method is required. A new wave peel tracking (WPT) method has been developed using a shore-based camera to assess surf amenity by measuring and quantifying potential surfing ride rate, length, duration, speed and direction on a wave-by-wave basis. The wave peel (or “curl” below the wave peak) is the optimal surfing region on a wave, and each wave peel track represents a surfable ride. Wave peel regions are identified, classified and tracked using traditional and machine learning-based computer vision techniques. The methodology is validated by comparing the rectified wave peel tracks with GPS-measured tracks from surfers in the wave peel regions. The WPT methodology is evaluated with data from a reef and adjacent natural beach at the Gold Coast, Australia. The reef produced longer ride lengths than the nearshore region and showed a consistent breaking location along the reef crest. Spatial maps of the wave peel tracks show the influence of tides on the wave breaking patterns and intensity. The WPT algorithm provides a robust, automated method for quantifying surf amenity to provide baseline data for surf break conservation. The methodology has potential uses to verify numerical modelling of surf breaks and to assess the impact of coastal development on surf breaks.

Particle Tracking Velocimetry Measurement of Bubble-Bubble Interaction

2003 ◽  
Author(s):  
Masa-aki Ashihara ◽  
Atsuhide Kitagawa ◽  
Masa-aki Ishikawa ◽  
Akihiro Nakashinchi ◽  
Yuichi Murai ◽  
...  
Keyword(s):  
Multiphase Flow ◽  
Particle Tracking ◽  
Particle Tracking Velocimetry ◽  
Volume Fraction ◽  
Vertical Wall ◽  
Measurement Data ◽  
Vertical Direction ◽  
Interaction Patterns ◽  
Bubble Interaction ◽  
Sliding Bubbles

Bubble-bubble interaction is a quite fundamental issue to understand multiphase flow dynamics and to improve mathematical models of dispersed multiphase flow for higher volume fraction of dispersion. In this study, the bubble-bubble interaction is measured using Particle Tracking Velocimetry (PTV) in various environments. First, bubbles sliding on a vertical wall are measured using 2-D PTV. Second, the free rising bubbles in an unbounded space are measured applying 3-D PTV. Third, the simultaneous measurement for gas and liquid phases in the layer of wall-sliding bubbles is carried out. The measurement data have shown that the average bubble-bubble interaction patterns in the wall-sliding bubbles and in the free rising bubbles were attractive in the vertical direction and repulsive in the horizontal direction. The relation between the carrier phase flow structure and the bubbles’ motion is detected to explain the mechanism of the bubble-bubble interaction.

scholarly journals LARGE-SCALE AND SMALL-SCALE EFFECTS IN WAVE BREAKING INTERACTION ON VERTICAL WALL ATTACHED WITH LARGE RECURVE PARAPET

2020 ◽  
pp. 22
Author(s):  
Rajendran Ravindar ◽  
V Sriram ◽  
Stefan Schimmels ◽  
Dimitris Stagonas
Keyword(s):  
Wave Breaking ◽  
Large Scale ◽  
Impact Force ◽  
Scale Effects ◽  
Vertical Wall ◽  
Impact Pressure ◽  
Scale Model ◽  
Small Scale ◽  
Scaling Method ◽  
The Impact

Two sets of experiments on the vertical wall attached with recurve parapets performed at 1:1 and 1:8 scale are compared to study the influence of scale, model and laboratory effects. The small-scale (1:8) experiment scaled to large-scale (1:1) using Froude scaling, and Cuomo et al. (2010) method are compared. Comparing both the methods for scaling impact pressure, Cuomo et al. (2010) predicts well in the impact zone, whereas Froude scaling is better in the up-rushing zone. In estimating integrated impact force, Froude scaling method over-estimates compared to Cuomo et al. (2010). Overall, Cuomo et al. (2010) work better for scaling up impact pressure and forces compared to Froude scaling method. These preliminary observations are based on one type of recurved parapets only.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/w9WipBjMWzw

Impact of New Slamming Wave Design Method on the Structural Dynamics of a Classic, Modern and Future Offshore Wind Turbine

2017 ◽  
Author(s):  
Johan M. Peeringa ◽  
Koen W. Hermans
Keyword(s):  
Wind Turbine ◽  
Wave Train ◽  
Breaking Waves ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Breaking Wave ◽  
Wave Loads ◽  
Wave Load ◽  
Wave Impact ◽  
The Impact

In the WiFi-JIP project, the impact of steep (and breaking) waves on a monopile support structure was studied. Observations during model tests showed that large tower top accelerations occur due to a slamming wave. Using experiments and simulations results, a new formulation of the design load for a slamming wave was developed. Instead of the embedded stream function, as applied in industry, the wave train is generated with the nonlinear potential flow code Oceanwave3D. On the wave train a set of conditions is applied to find the individual waves, that are closest to the prescribed breaking wave and most likely cause a slamming impact. To study the effect of the new slamming load formulation on different sized offshore wind turbines, aero-hydroelastic simulations were performed on a classic 3MW wind turbine, a modern 4MW wind turbine and a future 10MW wind turbine. The simulations are performed with and without a slamming wave load. The slamming has a clear effect on the tower top acceleration. Accelerations due to the wave impact are highest for the 3MW model at the tower top and at 50m height. A serious tower top acceleration of almost 7m/s2 due to wave slamming is found for the 3MW turbine. This is an increase of 474% compared with the case of Morison wave loads only.

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