scholarly journals Surface Drift Currents Induced by Waves and Wind in a Large Tank

2020 ◽  
Vol 50 (10) ◽  
pp. 3063-3073
Author(s):  
Vladislav Polnikov ◽  
Fangli Qiao ◽  
Hongyu Ma
Keyword(s):  
Friction Velocity ◽  
Wind Waves ◽  
Wave Spectrum ◽  
Stokes Drift ◽  
Wave Steepness ◽  
Measuring Surface ◽  
Mechanical Waves ◽  
Large Tank ◽  
First Time ◽  
Surface Drift

AbstractThe empirical features of surface drift currents induced by both mechanical and wind waves are presented. The measurements were made by using surface floats in a large tank with dimensions of 32.5 × 1 × 2 m3. Three cases were studied: (i) regular (narrowband) mechanical waves, (ii) irregular (wideband) mechanical waves, and (iii) wind waves. The measured surface drift currents induced by mechanical waves Ud are compared with the Stokes drift at the surface USt estimated by a well-known formula with an integral over the wave spectrum. In this case, the ratio Ud/USt varies in the range of 0.5–0.93 and slightly increases with decreasing wave steepness. No visible dependence on the breaking intensity is observed. In the case of wind waves, the wind-induced part of the surface drift Udw is compared with the friction velocity u*. In our measurements, the ratio Udw/u* varies systematically in the range of 0.65–1.2. Considering the percentage of wave breaking Br, the wave age A, and the wave steepness Ϭ, the parameterization of Udw was obtained in the form Udw = (Br + ϬA)u*, which corresponds to the observations with a mean error of 10%. For the first time, this ratio provides the dependence of wind-induced drift on the surface wave parameters. The obtained results and problems related to measuring surface drift currents are discussed.

Empirical Parameterization of the Wind-induced Drift Currents

2020 ◽  
Author(s):  
Vladislav Polnikov ◽  
Hongyu Ma
Keyword(s):  
Wind Waves ◽  
Wave Spectrum ◽  
Surface Wind ◽  
Wide Band ◽  
Stokes Drift ◽  
Wave Steepness ◽  
Mechanical Waves ◽  
Large Tank ◽  
First Time ◽  
Surface Drift

<p>Results of measurements of the drift currents induced by waves and wind at the wavy water surface are presented. The measurements were executed by means of surface floats in a large tank with the dimensions of 32.5x1x2 m<sup>3</sup>. Three cases were studied: (i) regular (narrow-band) mechanical waves; (ii) irregular (wide-band) mechanical waves; and (iii) wind waves.</p><p>The measured surface-drift currents induced by mechanical waves, U<sub>d</sub>, are compared with the Stokes drift at the surface, U<sub>St</sub>, estimated by the well-known formula with the integral over a wave spectrum. In this case, it was found that ratio U<sub>d</sub> / U<sub>St</sub> is varying in the range 0.5 – 0.93 and slightly growing with the decrease of wave steepness, having no visible dependence on the breaking intensity. These estimations are used to separate the wind-induced drift current, U<sub>dw</sub>, from the total drift at the presence of wind.</p><p>In the case of wind waves, the wind-induced part of the surface drift, U<sub>dw</sub>, is compared with the friction velocity, u<sub>*</sub>. In our measurements, the ratio U<sub>dw</sub> / u<sub>*</sub> varies systematically in the range 0.65 – 1.2. Taking into account the percentage of wave breaking, Br, the wave age, A, and the wave steepness, Ϭ = ak<sub>p</sub>, it was found the parameterization:  U<sub>dw</sub> = (Br + Ϭ A) u<sub>*</sub>, which corresponds to the observations with the mean error less than 10%. For the first time, this ratio provides the dependence of the surface wind drift on the surface wave parameters.</p>

scholarly journals Mutual Interaction between Surface Waves and Langmuir Circulations Observed in Wave-Resolving Numerical Simulations

2020 ◽  
Vol 50 (8) ◽  
pp. 2323-2339
Author(s):  
Yasushi Fujiwara ◽  
Yutaka Yoshikawa
Keyword(s):  
Surface Waves ◽  
Friction Velocity ◽  
Phase Speed ◽  
Mutual Interaction ◽  
Stokes Drift ◽  
Horizontal Shear ◽  
Budget Analysis ◽  
Vorticity Budget ◽  
Langmuir Circulations ◽  
The Waves

AbstractWave-resolving simulations of monochromatic surface waves and Langmuir circulations (LCs) under an idealized condition are performed to investigate the dynamics of wave–current mutual interaction. When the Froude number (the ratio of the friction velocity of wind stress imposed at the surface and wave phase speed) is large, waves become refracted by the downwind jet associated with LCs and become amplitude modulated in the crosswind direction. In such cases, the simulations using the Craik–Leibovich (CL) equation with a prescribed horizontally uniform Stokes drift profile are found to underestimate the intensity of LCs. Vorticity budget analysis reveals that horizontal shear of Stokes drift induced by the wave modulation tilts the wind-driven vorticity to the downwind direction, intensifying the LCs that caused the waves to be modulated. Such an effect is not reproduced in the CL equation unless the Stokes drift of the waves modulated by LCs is prescribed. This intensification mechanism is similar to the CL1 mechanism in that the horizontal shear of the Stokes drift plays a key role, but it is more likely to occur because the shear in this interaction is automatically generated by the LCs whereas the shear in the CL1 mechanism is retained only when a particular phase relation between two crossing waves is kept locked for many periods.

High Speed Rotating Shafts Design Algorithm

1993 ◽  
Author(s):  
Po Kee Wong
Keyword(s):  
Spectrum Analysis ◽  
High Speed ◽  
Wave Spectrum ◽  
Vibrational Modes ◽  
Elastic Rod ◽  
Design Algorithm ◽  
The Public ◽  
Rotating Shafts ◽  
First Time

Abstract This paper reveals an invention for the first time to the public about the fundamental concepts for the design of high speed rotating shafts based on the wave spectrum analysis of the vibrational modes of elastic circular rods and shells that was completed in 1967, even though the Pochhammer-Chree-Love solution of the transversal (n = 1) vibration of a solid elastic rod was originated by Pochhammer in 1876.

Covariate Extreme Value Analysis Using Wave Spectral Partitioning

2020 ◽  
Vol 37 (5) ◽  
pp. 873-888 ◽  
Author(s):  
Jesús Portilla-Yandún ◽  
Edwin Jácome
Keyword(s):  
Extreme Values ◽  
Wind Waves ◽  
Spectral Energy Distribution ◽  
Wave Spectrum ◽  
Wave Climate ◽  
Extreme Value ◽  
Extreme Value Analysis ◽  
Spectral Energy ◽  
Value Analysis ◽  
Spectral Partitioning

AbstractAn important requirement in extreme value analysis (EVA) is for the working variable to be identically distributed. However, this is typically not the case in wind waves, because energy components with different origins belong to separate data populations, with different statistical properties. Although this information is available in the wave spectrum, the working variable in EVA is typically the total significant wave height Hs, a parameter that does not contain information of the spectral energy distribution, and therefore does not fulfill this requirement. To gain insight in this aspect, we develop here a covariate EVA application based on spectral partitioning. We observe that in general the total Hs is inappropriate for EVA, leading to potential over- or underestimation of the projected extremes. This is illustrated with three representative cases under significantly different wave climate conditions. It is shown that the covariate analysis provides a meaningful understanding of the individual behavior of the wave components, in regard to the consequences for projecting extreme values.

scholarly journals Effect of Variations in Water Level and Wave Steepness on the Robustness of Wave Overtopping Estimation

2020 ◽  
Vol 8 (2) ◽  
pp. 63
Author(s):  
Nils B. Kerpen ◽  
Karl-Friedrich Daemrich ◽  
Oliver Lojek ◽  
Torsten Schlurmann
Keyword(s):  
Water Level ◽  
Wave Spectrum ◽  
Water Environment ◽  
Physical Modelling ◽  
Storm Surges ◽  
Water Levels ◽  
Coastal Protection ◽  
Wave Steepness ◽  
Wave Overtopping

The wave overtopping discharge at coastal defense structures is directly linked to the freeboard height. By means of physical modelling, experiments on wave overtopping volumes at sloped coastal structures are customarily determined for constant water levels and static wave steepness conditions (e.g., specific wave spectrum). These experiments are the basis for the formulation of empirically derived and widely acknowledged wave overtopping estimations for practical design purposes. By analysis and laboratory reproduction of typical features from exemplarily regarded real storm surge time series in German coastal waters, the role of non-stationary water level and wave steepness were analyzed and adjusted in experiments. The robustness of wave overtopping estimation formulae (i.e., the capabilities and limitations of such a static projection of dynamic boundary conditions) are outlined. Therefore, the classic static approach is contrasted with data stemming from tests in which both water level and wave steepness were dynamically altered in representative arrangements. The analysis reveals that mean overtopping discharges for simple sloping structures in an almost deep water environment could be robustly estimated for dynamic water level changes by means of the present design formulae. In contrast, the role of dynamic changes of the wave steepness led to a substantial discrepancy of overtopping volumes by a factor of two. This finding opens new discussion on methodology and criteria design of coastal protection infrastructure under dynamic exposure to storm surges and in lieu of alterations stemming from projected sea level rise.

scholarly journals Random wave-driven drag forces on near-bed vegetation in shallow water based on deepwater wind conditions

2019 ◽  
Vol 233 (4) ◽  
pp. 1287-1290
Author(s):  
Dag Myrhaug
Keyword(s):  
Shallow Water ◽  
Drag Force ◽  
Wind Waves ◽  
Wave Spectrum ◽  
Random Wave ◽  
Random Waves ◽  
Coastal Zones ◽  
Drag Forces ◽  
Mean Wind Speed ◽  
Wave Induced

This article provides a simple analytical method for giving estimates of random wave-driven drag forces on near-bed vegetation in shallow water from deepwater wind conditions. Results are exemplified using a Pierson–Moskowitz model wave spectrum for wind waves with the mean wind speed at the 10 m elevation above the sea surface as the parameter. The significant value of the drag force within a sea state of random waves is given, and an example typical for field conditions is presented. This method should serve as a useful tool for assessing random wave-induced drag force on vegetation in coastal zones and estuaries based on input from deepwater wind conditions.

scholarly journals Searching for chaotic deterministic features in laboratory water surface waves

2000 ◽  
Vol 7 (1/2) ◽  
pp. 37-48 ◽  
Author(s):  
M. Joelson ◽  
Th. Dudok de Wit ◽  
Ph. Dussouillez ◽  
A. Ramamonjiarisoa
Keyword(s):  
Surface Waves ◽  
Water Surface ◽  
Wind Waves ◽  
Theoretical Models ◽  
Resonant Interactions ◽  
Mechanical Waves ◽  
Random Character ◽  
Nonlinear Features ◽  
Low Dimensional ◽  
Laboratory Water

Abstract. The dynamic evolution of laboratory water surface waves has been studied within the framework of dynamical systems with the aim to identify stochastic or deterministic nonlinear features. Three different regimes are considered: pure wind waves, pure mechanical waves and mixed (wind and mechanical) waves. These three regimes show different dynamics. The results on wind waves do not clearly support the recently proposed idea that a deterministic Stokes-like component dominate the evolution of such waves; they are more appropriately described by a similarity-like approach that includes a random character. Cubic resonant interactions are clearly identified in pure mechanical waves using tricoherence functions. However, detailed aspects of the interactions do not fully agree with existing theoretical models. Finally, a deterministic motion is observed in mixed waves, which therefore are best described by a low dimensional nonlinear deterministic process.

scholarly journals Wind Sea and Swell Separation of 1D Wave Spectrum by a Spectrum Integration Method*

2012 ◽  
Vol 29 (1) ◽  
pp. 116-128 ◽  
Author(s):  
Paul A. Hwang ◽  
Francisco J. Ocampo-Torres ◽  
Héctor García-Nava
Keyword(s):  
Integration Method ◽  
Wave Spectrum ◽  
Peak Frequency ◽  
External Information ◽  
Wave Steepness ◽  
Wave Age ◽  
Wide Range ◽  
Wave Development ◽  
Wave Conditions ◽  
Wind Sea

Abstract In an earlier paper by Wang and Hwang, a wave steepness method was introduced to separate the wind sea and swell of the 1D wave spectrum without relying on external information, such as the wind speed. Later, the method was found to produce the unreasonable result of placing the swell–sea separation frequency higher than the wind sea peak frequency. Here, the following two factors causing the erratic performance are identified: (a) the wave steepness method defines the swell–sea separation frequency to be equal to the wind sea peak frequency with a wave age equal to one, and, (b) for more mature wave conditions, the peak frequency of the wave steepness function may not continue monotonic downshifting in high winds if the high-frequency portion of the wave spectrum has a spectral slope milder than −5. Conceptually, the swell–sea separation frequency should be placed between the swell and wind sea peak frequencies rather than at the wind sea peak frequency. Furthermore the wind sea wave age can vary over a considerable range, thus factor a above can lead to incorrect results. Also, because the slope of the wind sea equilibrium spectrum is typically close to −4, factor b becomes a serious restriction in more mature wave conditions. A spectrum integration method generalized from the wave steepness method is presented here for wind sea and swell separation of the 1D wave spectrum without requiring external information. The new spectrum integration method works very well over a wide range of wind wave development stages in the ocean.

Submillimeter Wave Spectrum of HS34SH

1989 ◽  
Vol 44 (8) ◽  
pp. 718-722 ◽  
Author(s):  
P. Mittler ◽  
G. Winnewisser ◽  
K. M. T. Yamada
Keyword(s):  
Wave Spectrum ◽  
Submillimeter Wave ◽  
Rotational Spectrum ◽  
Rotational Constants ◽  
Complete Set ◽  
First Time

Abstract The rotational spectrum of 34S-substituted disulfane, HS34SH, has been measured between 60 and 420 GHz, yielding for the first time the rotational constants A = 146694.949 MHz, B = 6779.018 MHz and C = 6776.339 MHz, together with a complete set of J4 and J6 distortion constants.

The Influence of Waves on Oil Spill Behavior

2009 ◽  
Author(s):  
Jung L. Lee ◽  
D. Y. Lee ◽  
I. H. Kim
Keyword(s):  
Oil Spill ◽  
Prediction Accuracy ◽  
Wind Waves ◽  
Wave Model ◽  
Stokes Drift ◽  
Wavelength Modulation ◽  
Operational Model ◽  
Mild Slope Equation ◽  
Linear Waves ◽  
Non Linear

In the present study, we include the wind generated wave module to improve the prediction accuracy of oil spill behavior under the stormy sea condition. The wind waves are simulated by using a new concept of wavelength modulation to enhance broader application of hyperbolic wave model of mild-slope equation type. The Hebei Spirit oil spill movements are accounted for by including the Stokes drift due to weakly non linear waves and simulated with an efficient operational model of GUI environments.

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