Non-Gaussian properties of second-order wave orbital velocity

Alberto Alberello; Amin Chabchoub; Odin Gramstad; Alexander V. Babanin; Alessandro Toffoli

doi:10.1016/j.coastaleng.2016.01.001

Non-Gaussian properties of second-order wave orbital velocity

Alberto Alberello, Amin Chabchoub, Odin Gramstad, Alexander V. Babanin, Alessandro Toffoli

Research output: Contribution to journal › Article › peer-review

15 Citations (Scopus)

Abstract

A stochastic second-order wave model is applied to assess the statistical properties of wave orbital velocity in random sea states below the water surface. Directional spreading effects as well as the dependency of the water depth are investigated by means of a Monte-Carlo approach. Unlike for the surface elevation, sub-harmonics dominate the second-order contribution to orbital velocity. We show that a notable set-down occurs for the most energetic and steepest groups. This engenders a negative skewness in the temporal evolution of the orbital velocity. A substantial deviation of the upper and lower tails of the probability density function from the Gaussian distribution is noticed; velocities are faster below the wave trough and slower below the wave crest when compared with linear theory predictions. Second-order nonlinearity effects strengthen with reducing the water depth, while weaken with the broadening of the wave spectrum. The results are confirmed by laboratory data. Corresponding experiments have been conducted in a large wave basin taking into account the directionality of the wave field. As shown, laboratory data are in very good agreement with the numerical prediction.

Original language	English
Pages (from-to)	42-49
Number of pages	8
Journal	Coastal Engineering
Volume	110
Early online date	4 Feb 2016
DOIs	https://doi.org/10.1016/j.coastaleng.2016.01.001
Publication status	Published - 1 Apr 2016
Externally published	Yes

Keywords

Second-order
Wave orbital motion
Wave statistics

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10.1016/j.coastaleng.2016.01.001

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title = "Non-Gaussian properties of second-order wave orbital velocity",

abstract = "A stochastic second-order wave model is applied to assess the statistical properties of wave orbital velocity in random sea states below the water surface. Directional spreading effects as well as the dependency of the water depth are investigated by means of a Monte-Carlo approach. Unlike for the surface elevation, sub-harmonics dominate the second-order contribution to orbital velocity. We show that a notable set-down occurs for the most energetic and steepest groups. This engenders a negative skewness in the temporal evolution of the orbital velocity. A substantial deviation of the upper and lower tails of the probability density function from the Gaussian distribution is noticed; velocities are faster below the wave trough and slower below the wave crest when compared with linear theory predictions. Second-order nonlinearity effects strengthen with reducing the water depth, while weaken with the broadening of the wave spectrum. The results are confirmed by laboratory data. Corresponding experiments have been conducted in a large wave basin taking into account the directionality of the wave field. As shown, laboratory data are in very good agreement with the numerical prediction.",

keywords = "Second-order, Wave orbital motion, Wave statistics",

author = "Alberto Alberello and Amin Chabchoub and Odin Gramstad and Babanin, {Alexander V.} and Alessandro Toffoli",

note = "Funding Information: This work was supported by the Swinburne University of Technology Postgraduate Research Award (SUPRA). Experiments were funded by the E.U. 7 th Framework Programme through the Integrated Infrastructure Initiative HYDRALAB IV (Contract No. 022441 ). A.A. and A.T. thank Miguel Onorato for valuable discussions on wave orbital motions. A.C. acknowledges support from the Burgundy Region and The Association of German Engineers (VDI). A.C. is an International Research Fellow of the Japan Society for the Promotion of Science (JSPS). Publisher Copyright: {\textcopyright} 2016 Elsevier B.V.",

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AU - Alberello, Alberto

AU - Chabchoub, Amin

AU - Gramstad, Odin

AU - Babanin, Alexander V.

AU - Toffoli, Alessandro

N1 - Funding Information: This work was supported by the Swinburne University of Technology Postgraduate Research Award (SUPRA). Experiments were funded by the E.U. 7 th Framework Programme through the Integrated Infrastructure Initiative HYDRALAB IV (Contract No. 022441 ). A.A. and A.T. thank Miguel Onorato for valuable discussions on wave orbital motions. A.C. acknowledges support from the Burgundy Region and The Association of German Engineers (VDI). A.C. is an International Research Fellow of the Japan Society for the Promotion of Science (JSPS). Publisher Copyright: © 2016 Elsevier B.V.

PY - 2016/4/1

Y1 - 2016/4/1

N2 - A stochastic second-order wave model is applied to assess the statistical properties of wave orbital velocity in random sea states below the water surface. Directional spreading effects as well as the dependency of the water depth are investigated by means of a Monte-Carlo approach. Unlike for the surface elevation, sub-harmonics dominate the second-order contribution to orbital velocity. We show that a notable set-down occurs for the most energetic and steepest groups. This engenders a negative skewness in the temporal evolution of the orbital velocity. A substantial deviation of the upper and lower tails of the probability density function from the Gaussian distribution is noticed; velocities are faster below the wave trough and slower below the wave crest when compared with linear theory predictions. Second-order nonlinearity effects strengthen with reducing the water depth, while weaken with the broadening of the wave spectrum. The results are confirmed by laboratory data. Corresponding experiments have been conducted in a large wave basin taking into account the directionality of the wave field. As shown, laboratory data are in very good agreement with the numerical prediction.

AB - A stochastic second-order wave model is applied to assess the statistical properties of wave orbital velocity in random sea states below the water surface. Directional spreading effects as well as the dependency of the water depth are investigated by means of a Monte-Carlo approach. Unlike for the surface elevation, sub-harmonics dominate the second-order contribution to orbital velocity. We show that a notable set-down occurs for the most energetic and steepest groups. This engenders a negative skewness in the temporal evolution of the orbital velocity. A substantial deviation of the upper and lower tails of the probability density function from the Gaussian distribution is noticed; velocities are faster below the wave trough and slower below the wave crest when compared with linear theory predictions. Second-order nonlinearity effects strengthen with reducing the water depth, while weaken with the broadening of the wave spectrum. The results are confirmed by laboratory data. Corresponding experiments have been conducted in a large wave basin taking into account the directionality of the wave field. As shown, laboratory data are in very good agreement with the numerical prediction.

KW - Second-order

KW - Wave orbital motion

KW - Wave statistics

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VL - 110

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JO - Coastal Engineering

JF - Coastal Engineering

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ER -

Non-Gaussian properties of second-order wave orbital velocity

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Keywords

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