Energy dissipation through wind-generated breaking waves

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.

Download Full-text

Estimating Energy Dissipation Rate from Breaking Waves Using Polarimetric SAR Images

Sensors ◽

10.3390/s20226540 ◽

2020 ◽

Vol 20 (22) ◽

pp. 6540

Author(s):

Rafael D. Viana ◽

João A. Lorenzzetti ◽

Jonas T. Carvalho ◽

Ferdinando Nunziata

Keyword(s):

Energy Dissipation ◽

Total Energy ◽

Dissipation Rate ◽

Temporal Distribution ◽

Wave Model ◽

Breaking Waves ◽

Fast Response ◽

Energy Dissipation Rate ◽

Sar Data ◽

Total Energy Dissipation

The total energy dissipation rate on the ocean surface, ϵt (W m−2), provides a first-order estimation of the kinetic energy input rate at the ocean–atmosphere interface. Studies on the spatial and temporal distribution of the energy dissipation rate are important for the improvement of climate and wave models. Traditional oceanographic research normally uses remote measurements (airborne and platforms sensors) and in situ data acquisition to estimate ϵt; however, those methods cover small areas over time and are difficult to reproduce especially in the open oceans. Satellite remote sensing has proven the potential to estimate some parameters related to breaking waves on a synoptic scale, including the energy dissipation rate. In this paper, we use polarimetric Synthetic Aperture Radar (SAR) data to estimate ϵt under different wind and sea conditions. The used methodology consisted of decomposing the backscatter SAR return in terms of two contributions: a polarized contribution, associated with the fast response of the local wind (Bragg backscattering), and a non-polarized (NP) contribution, associated with wave breaking (Non-Bragg backscattering). Wind and wave parameters were estimated from the NP contribution and used to calculate ϵt from a parametric model dependent of these parameters. The results were analyzed using wave model outputs (WAVEWATCH III) and previous measurements documented in the literature. For the prevailing wind seas conditions, the ϵt estimated from pol-SAR data showed good agreement with dissipation associated with breaking waves when compared to numerical simulations. Under prevailing swell conditions, the total energy dissipation rate was higher than expected. The methodology adopted proved to be satisfactory to estimate the total energy dissipation rate for light to moderate wind conditions (winds below 10 m s−1), an environmental condition for which the current SAR polarimetric methods do not estimate ϵt properly.

Download Full-text

Spectrally Resolved Energy Dissipation Rate and Momentum Flux of Breaking Waves

Journal of Physical Oceanography ◽

10.1175/2007jpo3762.1 ◽

2008 ◽

Vol 38 (6) ◽

pp. 1296-1312 ◽

Cited By ~ 77

Author(s):

Johannes R. Gemmrich ◽

Michael L. Banner ◽

Chris Garrett

Keyword(s):

Energy Dissipation ◽

Wave Field ◽

Wave Energy ◽

Dissipation Rate ◽

Momentum Flux ◽

Phase Speed ◽

Breaking Waves ◽

Energy Dissipation Rate ◽

Small Scale ◽

Breaking Wave

Abstract Video observations of the ocean surface taken from aboard the Research Platform FLIP reveal the distribution of the along-crest length and propagation velocity of breaking wave crests that generate visible whitecaps. The key quantity assessed is Λ(c)dc, the average length of breaking crests per unit area propagating with speeds in the range (c, c + dc). Independent of the wave field development, Λ(c) is found to peak at intermediate wave scales and to drop off sharply at larger and smaller scales. In developing seas breakers occur at a wide range of scales corresponding to phase speeds from about 0.1 cp to cp, where cp is the phase speed of the waves at the spectral peak. However, in developed seas, breaking is hardly observed at scales corresponding to phase speeds greater than 0.5 cp. The phase speed of the most frequent breakers shifts from 0.4 cp to 0.2 cp as the wave field develops. The occurrence of breakers at a particular scale as well as the rate of surface turnover are well correlated with the wave saturation. The fourth and fifth moments of Λ(c) are used to estimate breaking-wave-supported momentum fluxes, energy dissipation rate, and the fraction of momentum flux supported by air-entraining breaking waves. No indication of a Kolmogorov-type wave energy cascade was found; that is, there is no evidence that the wave energy dissipation is dominated by small-scale waves. The proportionality factor b linking breaking crest distributions to the energy dissipation rate is found to be (7 ± 3) × 10−5, much smaller than previous estimates.

Download Full-text

The Features of Energy Dissipation of Spilling and Plunging Breaking Waves

Springer Proceedings in Earth and Environmental Sciences - Physical and Mathematical Modeling of Earth and Environment Processes (2018) ◽

10.1007/978-3-030-11533-3_27 ◽

2019 ◽

pp. 278-286

Author(s):

V. V. Volkova ◽

Ya. V. Saprykina

Keyword(s):

Energy Dissipation ◽

Breaking Waves

Download Full-text

Energy Dissipation by Breaking Waves

Journal of Physical Oceanography ◽

10.1175/1520-0485(1994)024<2041:edbbw>2.0.co;2 ◽

1994 ◽

Vol 24 (10) ◽

pp. 2041-2049 ◽

Cited By ~ 92

Author(s):

W. Kendall Melville

Keyword(s):

Energy Dissipation ◽

Breaking Waves

Download Full-text

OIL DROPLET SIZE DISTRIBUTION AS A FUNCTION OF ENERGY DISSIPATION RATE IN AN EXPERIMENTAL WAVE TANK

International Oil Spill Conference Proceedings ◽

10.7901/2169-3358-2008-1-621 ◽

2008 ◽

Vol 2008 (1) ◽

pp. 621-626 ◽

Cited By ~ 16

Author(s):

Zhengkai Li ◽

Kenneth Lee ◽

Thomas King ◽

Michel C. Boufadel ◽

Albert D. Venosa

Keyword(s):

Energy Dissipation ◽

Size Distribution ◽

Dissipation Rate ◽

Droplet Size Distribution ◽

Breaking Waves ◽

Energy Dissipation Rate ◽

Wave Tank ◽

Chemical Dispersant ◽

Dispersed Oil ◽

Dispersant Effectiveness

ABSTRACT The U.S. National Research Council (NRC) Committee on Understanding Oil Spill Dispersants: Efficacy and Effects (2005) identified two factors that require further investigation in chemical oil dispersant efficacy studies: 1) quantification of mixing energy at sea as energy dissipation rate and 2) dispersed particle size distribution. To fully evaluate the significance of these factors, a wave tank facility was designed and constructed to conduct controlled oil dispersion studies. A factorial experimental design was used to study the dispersant effectiveness as a function of energy dissipation rate for two oils and two dispersants under three different wave conditions, namely regular non-breaking waves, spilling breakers, and plunging breakers. The oils tested were weathered MESA and fresh ANS crude. The dispersants tested were Corexit 9500 and SPC 1000 plus water for no-dispersant control. The wave tank surface energy dissipatation rates of the three waves were determined to be 0.005, 0.1, and 1 m2/s3, respectively. The dispersed oil concentrations and droplet size distribution, measured by in-situ laser diffraction, were compared to quantify the chemical dispersant effectiveness as a function of energy dissipation rate. The results indicate that high energy dissipation rate of breaking waves enhanced chemical dispersant effectiveness by significantly increasing dispersed oil concentration and reducing droplet sizes in the water column (p <0.05). The presence of dispersants and breaking waves stimulated the oil dispersion kinetics. The findings of this research are expected to provide guidance to disperant application on oil spill responses.

Download Full-text