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Turbulent viscosity in natural surf zones ArchiMer
Grasso, Florent; Ruessink, B. G..
Waves breaking in the shallow surf zone near the shoreline inject turbulence into the water column that may reach the bed to suspend sediment. Breaking-wave turbulence in the surf zone is, however, poorly understood, which is one of the reasons why many process-based coastal-evolution models predict coastal change during severe storms inadequately. Here, we use data collected in two natural surf zones to derive a new parameterization for the stability function C-mu that determines the magnitude of the eddy viscosity nu(t) in two-equation turbulent-viscosity models, nu(t) = C(mu)k(2)/epsilon, where k is turbulent kinetic energy and epsilon is the turbulence dissipation rate. In both data sets, the ratio of turbulence production to dissipation is small...
Tipo: Text Palavras-chave: Eddy viscosity; Field measurements; Parameterization; Production; Surf zone; Turbulence.
Ano: 2012 URL: https://archimer.ifremer.fr/doc/00114/22512/20204.pdf
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Wave spectrum retrieval from airborne sunglitter images ArchiMer
Yurovskaya, Maria; Rascle, Nicolas; Kudryavtsev, Vladimir; Chapron, Bertrand; Marie, Louis; Molemaker, Jeroen.
Reconstruction and evolution of two-dimensional spectra of surface waves in the Gulf of Mexico are derived from airborne sun-glitter imagery. As the proposed method is based on a linear transfer function deduced from the shape of the sunglitter brightness, the absolute wavenumber elevation spectrum does not require any additional assumption or information about sky brightness, wind or wave energy. The detailed description of the airborne image processing method is given. As demonstrated, retrieved spectra agree well with nearby NDBC buoy data, both for spectrum shape, level and energy angular distribution. The 180-degree wave direction ambiguity, inherent to image-derived spectra, is eliminated by using cross-correlation analysis between two consecutive...
Tipo: Text Palavras-chave: Sunglitter; Sea surface waves; Directional wave spectrum; Aerial photography; Field measurements; Remote sensing observations; High resolution; Drone.
Ano: 2018 URL: https://archimer.ifremer.fr/doc/00465/57712/60174.pdf
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Directional short wind wave spectra derived from the sea surface photography ArchiMer
Yurovskaya, M. V.; Dulov, V. A.; Chapron, Bertrand; Kudryavtsev, V. N..
New field measurements of 2-D wave number short wind wave spectra in the wavelength range from few millimeters to few decimeters are reported and discussed. The measurement method is based on stereophotography and image brightness contrast processing. As found, the spectra of decimeter waves are almost isotropic and weakly dependent on the wind speed. Both directional anisotropy and wind sensitivity rapidly increase at wave numbers larger than 100 rad/m. These aspects are consistent with other previously reported optical and radar data. Following these new in situ measurements, a revision of a semiempirical model of short wind wave spectrum is suggested. This revised model can readily be implemented in other studies (radar scattering, air-sea interaction...
Tipo: Text Palavras-chave: Wave directional spectrum; Field measurements; Spectrum modeling; Gravity-capillary waves; Image processing.
Ano: 2013 URL: http://archimer.ifremer.fr/doc/00164/27566/25927.pdf
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