Numerical Investigation of Spectral Evolution of Wind Waves. Part I: Wind-Input Source Function

2010 ◽  
Vol 40 (4) ◽  
pp. 656-666 ◽  
Author(s):  
K. N. Tsagareli ◽  
A. V. Babanin ◽  
D. J. Walker ◽  
I. R. Young
Keyword(s):  
Field Data ◽  
Source Function ◽  
Source Term ◽  
Wind Waves ◽  
The Novel ◽  
Spectral Evolution ◽  
Input Source ◽  
Wind Input ◽  
Strong Winds ◽  
Lake George

Abstract This paper is dedicated to the investigation and calibration of the parameterized form for the wind-input source term Sin proposed earlier on the basis of field observations at Lake George, Australia. The main objective of this study was to obtain spectral forms for the wind-input source function Sin, which incorporates the novel observation-based features and at the same time satisfies the important physical constraint that the total integrated wind input must agree with independently observed magnitudes of the wind stress. Within this approach, a new methodology, a dynamic self-adjusting routine, was developed for correction of the wind-input source function Sin. This correction involves a frequency-dependent adjustment to the growth rate γ( f ), based on extrapolations from field data. The model results also show that light winds require higher-rate adjustments of the wind input than strong winds.

scholarly journals Adjusting of Wind Input Source Term in WAVEWATCH III Model for the Middle-Sized Water Body on the Basis of the Field Experiment

2016 ◽  
Vol 2016 ◽  
pp. 1-13 ◽  
Author(s):  
Alexandra Kuznetsova ◽  
Georgy Baydakov ◽  
Vladislav Papko ◽  
Alexander Kandaurov ◽  
Maxim Vdovin ◽  
...  
Keyword(s):  
Wind Speed ◽  
Field Experiment ◽  
Water Body ◽  
Source Term ◽  
Wind Waves ◽  
Surface Wind ◽  
Simulated Data ◽  
Wavewatch Iii ◽  
Input Source ◽  
Wind Input

Adjusting of wind input source term in numerical model WAVEWATCH III for the middle-sized water body is reported. For this purpose, the field experiment on Gorky Reservoir is carried out. Surface waves are measured along with the parameters of the airflow. The measurement of wind speed in close proximity to the water surface is performed. On the basis of the experimental results, the parameterization of the drag coefficient depending on the 10 m wind speed is proposed. This parameterization is used in WAVEWATCH III for the adjusting of the wind input source term within WAM 3 and Tolman and Chalikov parameterizations. The simulation of the surface wind waves within tuned to the conditions of the middle-sized water body WAVEWATCH III is performed using three built-in parameterizations (WAM 3, Tolman and Chalikov, and WAM 4) and adjusted wind input source term parameterizations. Verification of the applicability of the model to the middle-sized reservoir is performed by comparing the simulated data with the results of the field experiment. It is shown that the use of the proposed parameterizationCD(U10)improves the agreement in the significant wave heightHSfrom the field experiment and from the numerical simulation.

Ocean Wave Non-Linearity and Wind Input in Directional Seas: Energy Input During Wave-Group Focussing

2018 ◽  
Author(s):  
Thomas A. A. Adcock ◽  
Paul H. Taylor
Keyword(s):  
Energy Input ◽  
Wind Waves ◽  
Rogue Waves ◽  
Wave Group ◽  
Spectral Evolution ◽  
Wave Groups ◽  
Small Influence ◽  
Non Linear ◽  
Linear Effects ◽  
Wind Input

There has been speculation that energy input (wind) can play an important role in the formation of rogue waves in the open ocean. Here we examine the role energy input can play by adding energy to the modified non-linear Schrödinger equation. We consider NewWave type wave-groups with spectra which are realistic for wind waves. We examine the case where energy input is added to the group as the wave-group focuses. We consider whether this energy input can cause significant non-linear effects to the subsequent spatial and spectral evolution. For the parameters considered here we find this to have only a small influence.

scholarly journals Wave boundary layer model in SWAN revisited

2018 ◽  
Author(s):  
Jianting Du ◽  
Rodolfo Bolaños ◽  
Xiaoli Guo Larsén ◽  
Mark Kelly
Keyword(s):  
Source Function ◽  
Wind Profile ◽  
Source Terms ◽  
Original Source ◽  
Input Source ◽  
Mean Wave Period ◽  
Wind Input ◽  
Wave Induced ◽  
The Impact ◽  
Wave Boundary

Abstract. In this study we extend the work presented in Du et al. (2017) to make the WBLM applicable for real cases by improving the wind input and white-capping dissipation source functions. Improvement via the new source terms includes three aspects. First, the WBLM wind-input source function is developed by considering the impact of wave-induced wind profile variation on the estimation of wave growth rate. Second, the white-capping dissipation source function is revised to be not explicitly dependent on wind speed for real wave simulations. Third, several improvements are made to the numerical WBLM algorithm, which increase the model's numerical stability and computational efficiency. The improved WBLM wind-input and white-capping dissipation source functions are calibrated through idealized fetch-limited and depth-limited studies, and validated in real wave simulations during two North Sea storms. The new WBLM source terms show better performance in the simulation of significant wave height and mean wave period than the original source terms.

scholarly journals Balanced source terms for wave generation within the Hasselmann equation

2017 ◽  
Vol 24 (4) ◽  
pp. 581-597 ◽  
Author(s):  
Vladimir Zakharov ◽  
Donald Resio ◽  
Andrei Pushkarev
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Source Term ◽  
Similarity Analysis ◽  
Source Terms ◽  
Self Similarity ◽  
The World ◽  
Theoretical Predictions ◽  
Input Source ◽  
Wind Input

Abstract. The new Zakharov–Resio–Pushkarev (ZRP) wind input source term Zakharov et al.(2012) is examined for its theoretical consistency via numerical simulation of the Hasselmann equation. The results are compared to field experimental data, collected at different sites around the world, and theoretical predictions based on self-similarity analysis. Consistent results are obtained for both limited fetch and duration limited statements.

scholarly journals On ZRP wind input term consistency in Hasselmann equation

2016 ◽  
Author(s):  
Vladimir Zakharov ◽  
Donald Resio ◽  
Andrei Pushkarev
Keyword(s):  
Experimental Data ◽  
Time Domain ◽  
Source Term ◽  
Similarity Analysis ◽  
Self Similarity ◽  
The World ◽  
Theoretical Predictions ◽  
Input Source ◽  
Wind Input ◽  
Good Agreement

Abstract. The new ZRP wind input source term (Zakharov et al., 2012) is checked for its consistency via numerical simulation of Hasselmann equation. The results are compared to field experimental data, collected at different sites around the world, and theoretical predictions of self-similarity analysis. Good agreement is obtained for limited fetch and time domain statements.

Wave-Follower Field Measurements of the Wind-Input Spectral Function. Part II: Parameterization of the Wind Input

2006 ◽  
Vol 36 (8) ◽  
pp. 1672-1689 ◽  
Author(s):  
Mark A. Donelan ◽  
Alexander V. Babanin ◽  
Ian R. Young ◽  
Michael L. Banner
Keyword(s):  
Water Waves ◽  
Source Function ◽  
Field Measurements ◽  
Wave Steepness ◽  
Outer Flow ◽  
Wide Range ◽  
Input Source ◽  
Wind Input ◽  
Wave Induced ◽  
The Waves

Abstract Nearly all of the momentum transferred from wind to waves comes about through wave-induced pressure acting on the slopes of waves: known as form drag. Direct field measurements of the wave-induced pressure in airflow over water waves are difficult and consequently rare. Those that have been reported are for deep water conditions and conditions in which the level of forcing, measured by the ratio of wind speed to the speed of the dominant (spectral peak) waves, is quite weak, U10/cp < 3. The data reported here were obtained over a large shallow lake during the Australian Shallow Water Experiment (AUSWEX). The propagation speeds of the dominant waves were limited by depth and the waves were correspondingly steep. This wider range of forcing and concomitant wave steepness revealed some new aspects of the rate of wave amplification by wind, the so-called wind input source function, in the energy balance equation for wind-driven water waves. It was found that the exponential growth rate parameter (fractional energy increase per radian) depended on the slope of the waves, ak, vanishing as ak → 0. For very strong forcing a condition of “full separation” occurs, where the airflow detaches from the crests and reattaches on the windward face leaving a separation zone over the leeward face and the troughs. In a sense, the outer flow does not “see” the troughs and the resulting wave-induced pressure perturbation is much reduced, leading to a reduction in the wind input source function relative to that obtained by extrapolation from more benign conditions. The source function parameterized on wave steepness and degree of separation is shown to be in agreement with previous field and laboratory data obtained in conditions of much weaker forcing and wave steepness. The strongly forced steady-state conditions of AUSWEX have enabled the authors to define a generalized wind input source function that is suitable for a wide range of conditions.

Source Term Balance for Finite Depth Wind Waves

2000 ◽  
Author(s):  
Ian R. Young ◽  
Michael L. Banner ◽  
Mark M. Donelan
Keyword(s):  
Source Term ◽  
Wind Waves ◽  
Finite Depth

scholarly journals Global characteristics of auroral Hall currents derived from the Swarm constellation: dependences on season and IMF orientation

2017 ◽  
Vol 35 (6) ◽  
pp. 1249-1268 ◽  
Author(s):  
Tao Huang ◽  
Hermann Lühr ◽  
Hui Wang
Keyword(s):  
Magnetic Field ◽  
Hall Current ◽  
Flow Direction ◽  
Magnetic Activity ◽  
The Novel ◽  
Polar Cap ◽  
Magnetic Field Data ◽  
Electrojet Current ◽  
Wind Input ◽  
The Imf

Abstract. On the basis of field-aligned currents (FACs) and Hall currents derived from high-resolution magnetic field data of the Swarm constellation, the average characteristics of these two current systems in the auroral regions are comprehensively investigated by statistical methods. This is the first study considering both current types determined simultaneously by the same spacecraft in both hemispheres. The FAC distribution, derived from the novel Swarm dual-spacecraft approach, reveals the well-known features of Region 1 (R1) and Region 2 (R2) FACs. At high latitudes, Region 0 (R0) FACs appear on the dayside. Their flow direction, up or down, depends on the orientation of the interplanetary magnetic field (IMF) By component. Of particular interest is the distribution of auroral Hall currents. The prominent auroral electrojets are found to be closely controlled by the solar wind input, but we find no dependence of their intensity on the IMF By orientation. The eastward electrojet is about 1.5 times stronger in local summer than in winter. Conversely, the westward electrojet shows less dependence on season. As to higher latitudes, part of the electrojet current is closed over the polar cap. Here the seasonal variation of conductivity mainly controls the current density. During local summer of the Northern Hemisphere, there is a clear channeling of return currents over the polar cap. For positive (negative) IMF By a dominant eastward (westward) Hall current circuit is formed from the afternoon (morning) electrojet towards the dawn side (dusk side) polar cap return current. The direction of polar cap Hall currents in the noon sector depends directly on the orientation of the IMF By. This is true for both signs of the IMF Bz component. Comparable Hall current distributions can be observed in the Southern Hemisphere but for opposite IMF By signs. Around the midnight sector the westward substorm electrojet is dominating. As expected, it is highly dependent on magnetic activity, but it shows only little response to season and IMF By polarity. An important finding is that all the IMF By dependences of FACs and Hall currents practically disappear in the dark winter hemisphere.

Implementing New Nonlinear Term in Third Generation Wave Models

2014 ◽  
Author(s):  
Odin Gramstad ◽  
Alexander Babanin
Keyword(s):  
Kinetic Equation ◽  
Spread Spectrum ◽  
Time Scale ◽  
Source Term ◽  
Wave Spectrum ◽  
Wave Model ◽  
Third Generation ◽  
Spectral Evolution ◽  
Linear Interaction ◽  
Wavewatch Iii

The non-linear interaction term is one of the three key source functions in every third-generation spectral wave model. An update of physics of this term is discussed. The standard statistical/phase-averaged description of the nonlinear transfer of energy in the wave spectrum (wave-turbulence) is based on Hasselmann’s kinetic equation [1]. In the derivation of the kinetic equation (KE) it is assumed that the evolution takes place on the slow O(ε−4) time scale, where ε is the wave steepness. This excludes the effects of near-resonant quartet interactions that may lead to spectral evolution on the ‘fast’ O(ε−2) time scale. Generalizations of the KE (GKE) that enable description of spectral evolution on the O(ε−2) time scale [2–4] are discussed. The GKE, first solved numerically in [4], is implemented as a source term in the third generation wave model WAVEWATCH-III. The new source term (GKE) is tested and compared to the other nonlinear-interaction source terms in WAVEWATCH-III; the full KE (WRT method) and the approximate DIA method. It is shown that the GKE gives similar results to the KE in the case of a relatively broad banded and directional spread spectrum, while it shows somewhat larger difference in the case of a more narrow banded spectrum with narrower directional distribution. We suggest that the GKE may be a suitable replacement to the KE in situations where ‘fast’ spectral evolution takes place.

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