SPECTRAL WAVE MODELLING IN TIDAL INLET SEAS: RESULTS FROM THE SBW WADDEN SEA PROJECT

2011 ◽  
Vol 1 (32) ◽  
pp. 44 ◽  
Author(s):  
Ap Van Dongeren ◽  
Andre Van der Westhuysen ◽  
Jacco Groeneweg ◽  
Gerbrant Van Vledder ◽  
Joost Lansen ◽  
...  
Keyword(s):  
Wave Height ◽  
Wave Breaking ◽  
Wadden Sea ◽  
Low Frequency ◽  
Wave Model ◽  
Finite Depth ◽  
Transformation Model ◽  
Wave Transformation ◽  
Sea Waves ◽  
Wave Conditions

Over the last five years a research program has been carried out to assess the performance of the spectral wave model SWAN in the Wadden Sea so that it may be used for the transformation of offshore wave conditions to wave boundary conditions near the sea defenses (dikes and dunes). The assessment was done on the basis of extensive wave measurements conducted in Ameland inlet and the Dutch Eastern Wadden Sea, as well as relevant data from lakes and estuaries. After a first round of assessment, we found that SWAN performed reasonably well for storm conditions but three aspects required further attention. Firstly, focusing on the main channel, SWAN formulations needed to be modified in order to eliminate overprediction of the significant wave height in opposing currents. Secondly, the primary spectral peak of North Sea waves penetrating into the inlet was underpredicted. Best results were obtained when the refraction of low-frequency waves was limited and the bottom friction coefficient was set at a lower value than the current default for wind seas. Thirdly, over the tidal flats the computed ratio of integral wave height over water depth showed an apparent upper limit using the conventional Battjes and Janssen (1978) depth-limited wave breaking formulation, because the wave growth over finite depth is hampered by the present formulation of depth-induced wave breaking. The problem has been solved using a new breaker formulation. All these improvements have lead to a wave transformation model with which reliable wave conditions in the Wadden Sea and related complex areas can be determined.

Research and Analysis on the Wave Transformation and Irregular Wave Breaking Criterion on the Shore

2016 ◽  
Vol 858 ◽  
pp. 354-358
Author(s):  
Tao You ◽  
Li Ping Zhao ◽  
Zheng Xiao ◽  
Lun Chao Huang ◽  
Xiao Rui Han
Keyword(s):  
Theoretical Model ◽  
Wave Height ◽  
Wave Breaking ◽  
Surf Zone ◽  
Breaking Waves ◽  
Wave Transformation ◽  
Breaking Wave ◽  
Height Distribution ◽  
Flume Experiments ◽  
Irregular Wave

Within the surf zone which is the region extending from the seaward boundary of wave breaking to the limit of wave uprush, breaking waves are the dominant hydrodynamics acting as the key role for sediment transport and beach profile change. Breaking waves exhibit various patterns, principally depending on the incident wave steepness and the beach slope. Based on the equations of conservation of mass, momentum and energy, a theoretical model for wave transformation in and outside the surf zone was obtained, which is used to calculate the wave shoaling, wave set-up and set down and wave height distributions in and outside the surf zone. The analysis and comparison were made about the breaking point location and the wave height variation caused by the wave breaking and the bottom friction, and about the wave breaking criterion under regular and irregular breaking waves. Flume experiments relating to the regular and irregular breaking wave height distribution across the surf zone were conducted to verify the theoretical model. The agreement is good between the theoretical and experimental results.

scholarly journals IRREGULAR WAVE TRANSFORMATION AFFECTED BY OPPOSING CURRENTS

1986 ◽  
Vol 1 (20) ◽  
pp. 53
Author(s):  
Shigeki Sakai ◽  
Kouestu Hiyamizu ◽  
Hiroshi Saeki
Keyword(s):  
Wave Height ◽  
Present Model ◽  
Surf Zone ◽  
Transformation Model ◽  
Irregular Waves ◽  
Wave Transformation ◽  
Irregular Wave ◽  
Sea Bed ◽  
Dimensionless Unit ◽  
Deep Water Wave

Transformation of irregular waves affected by opposing currents on a sloping sea bed was discussed, experimentally and theoretically. It was found that representative values of wave height, such as a significant wave height, are larger before breaking and the wave height decaying occurs more promptly in a surf zone as opposing currents become dominant, and that characteristics of a irregular wave transformation are determined by the dimensionless unit width discharge q* and the deep water wave steepness. This means that the effects of opposing currents on irregular wave transformation are qualitatively identical to that on the regular waves. A transformation model of irregular waves affected by opposing currents was presented. In the model, formulations for a regular wave transformation, in which the effects of opposing currents were taken into account, were applied to individual waves defined by zero-down" cross-method from irregular wave profiles. Comparisons between experimental results and the prediction by the model showed that the present model gives a good explanation for wave height distributions and the experimental finding that the surf zone is moved offshore by opposing currents.

scholarly journals THE EXACT SOLUTION OF THE HIGHEST WAVE DERIVED FROM A UNIVERSAL WAVE MODEL

1984 ◽  
Vol 1 (19) ◽  
pp. 70
Author(s):  
Yang Yih Chen ◽  
Frederick L.W. Tang
Keyword(s):  
Exact Solution ◽  
Solitary Wave ◽  
Gravity Wave ◽  
Wave Height ◽  
Water Depth ◽  
Series Solution ◽  
Wave Model ◽  
Finite Depth

The solitary wave is first established in this paper by extending the series solution of periodic gravity wave as the wavelength approaches to infinite. Then, the highest gravity wave of permanent type in finite depth of water is immediately analyzed. The maximum ratio of wave height to water depth is obtained as 0.85465')..., and the angle at the crest for the considered highest wave is estimated to be 90°.

scholarly journals ON SPECTRUM CALIBRATION FOR NEARSHORE WAVE TRANSFORMATION

2018 ◽  
pp. 50
Author(s):  
Zhong Peng ◽  
Jill Bradon
Keyword(s):  
Wave Height ◽  
Significant Wave Height ◽  
Wave Spectrum ◽  
Wave Model ◽  
Accurate Solution ◽  
Least Square ◽  
Wave Transformation ◽  
Wave Spectra ◽  
Wave Modelling ◽  
Spectrum Calibration

A ‘shape-focus’ method is proposed for wave spectrum calibration. In this method calibration factors at each frequency bin are derived from measured and modelled data using a least square error approach. Modelled wave spectra are calibrated using the shape-focus method and then applied to a SWAN wave model to simulate nearshore wave transformation. Nearshore wave spectra are then compared with measurements. Results show that spectrum calibration with the shape-focus method improves wave data accuracy significantly for both significant wave height and mean wave periods, thus provides a more accurate solution to calibrating wave spectra for nearshore wave modelling.

scholarly journals LABORATORY EXPERIMENTS OF BICHROMATIC WAVE GROUPS PROPAGATION ON A GENTLE SLOPE BEACH PROFILE AND ENERGY TRANSFER TO LOW AND HIGH FREQUENCY COMPONENTS

2017 ◽  
pp. 6 ◽  
Author(s):  
Enrique M Padilla ◽  
Jose M Alsina
Keyword(s):  
High Frequency ◽  
Wave Breaking ◽  
Low Frequency ◽  
Primary Wave ◽  
Wave Group ◽  
Wave Groups ◽  
Long Wave ◽  
Wave Conditions ◽  
Hf Wave ◽  
Nonlinear Energy

This work presents a first analysis of experimental data studying the influence of the frequency bandwidth on the propagation of bichromatic wave groups over a constant 1:100 beach slope. The use of a large spatial cross-shore resolution and Bi-Spectral analysis techniques allows the identification of nonlinear energy transfers along the propagation of wave groups. During wave-group shoaling, nonlinear coupling between the primary wave frequencies results in a larger growth of superharmonics for narrow-banded wave conditions, increasing the skewness of the wave and leading to eventual instabilities and earlier high frequency (hf) wave breaking compared to the broad-banded wave condition. Regarding the growth of low frequency (lf) component, the data analysis has shown a larger growth of the incident bound long wave (IBLW) for broad-banded wave conditions. It is generally assumed that the transferred energy from the primary wave components to subharmonics does not affect the short wave energy budget. Here, the opposite is hypothesised, and a larger growth of the IBLW for broad-banded wave conditions is accompanied of a larger reduction of the primary wave components, a reduced growth of hf components and, consequently, a reduction in the growth of hf wave asymmetry during wave group shoaling. Conversely for narrow-banded wave conditions, a reduced IBLW growth is associated with a larger growth of hf wave asymmetry. After hf wave breaking, within the low frequency domain (lf), the IBLW decays slightly for narrow-banded conditions, consistent with a reduction in radiation stress forcing. This involves a nonlinear energy transfer from the wave group frequency back to hf components. The remaining lf energy, Outgoing Free Long Wave (OFLW), reflects back at the shoreline. However, for broad-banded wave conditions, strong dissipation and minimal reflection of lf components occurs close to the shoreline, which might be caused by lf wave breaking.

scholarly journals Assessing the Performance of the Dissipation Parameterizations in WAVEWATCH III Using Collocated Altimetry Data

2009 ◽  
Vol 39 (11) ◽  
pp. 2800-2819 ◽  
Author(s):  
Georgia D. Kalantzi ◽  
Christine Gommenginger ◽  
Meric Srokosz
Keyword(s):  
Wave Height ◽  
Wave Breaking ◽  
Source Term ◽  
Wave Spectrum ◽  
Wave Model ◽  
North Indian Ocean ◽  
Altimeter Data ◽  
Wave Direction ◽  
Wavewatch Iii ◽  
The North

Abstract Wave-breaking dissipation is one of the least understood processes implemented in contemporary wave models. Significant effort has been put in its parameterization, but it has not proven to be totally satisfactory, either theoretically or practically. In this work, the WAVEWATCH III (version 2.22; Tolman) wave model is used to evaluate the two wind input/dissipation source term packages that it includes: (i) Wave Model (WAM) cycle 3 (WAMDIG) and (ii) Tolman and Chalikov. Global model outputs were obtained under the same wind forcing for the two dissipation formulations and were collocated in space and time in the north Indian Ocean with Ocean Topography Experiment (TOPEX) altimeter data. The performance of the model was assessed by evaluating the statistical behavior of the collocated datasets. The parameters examined were significant wave height, wind speed, wind direction, wave direction, wave height for fully developed seas, and energy loss due to wave breaking. From the results, the behavior of the input/dissipation formulations in specific wind and wave conditions was identified; that is, the results give insight to the way the two source term packages “work” and how they respond to local wind sea or swell. Specifically, both of the packages were unable to perform adequately during a season when the area can be mostly affected by swell. However, the results confirmed that the examination of only integral spectral wave parameters does not give information on the inherent physical characteristics of the formulations. Further study, on the basis of point spectra, is necessary to examine the formulations’ performance across the wave spectrum.

scholarly journals Radar Remote Sensing Estimates of Waves and Wave Forcing at a Tidal Inlet

2015 ◽  
Vol 32 (4) ◽  
pp. 842-854 ◽  
Author(s):  
Guillermo M. Díaz Méndez ◽  
Merrick C. Haller ◽  
Britt Raubenheimer ◽  
Steve Elgar ◽  
David A. Honegger
Keyword(s):  
Remote Sensing ◽  
Wave Height ◽  
Wave Breaking ◽  
Tidal Inlet ◽  
Wave Transformation ◽  
Radar Remote Sensing ◽  
Wave Forcing ◽  
X Band ◽  
Mean Square Errors

AbstractThe time and space variability of wave transformation through a tidal inlet is investigated with radar remote sensing. The frequency of wave breaking and the net wave breaking dissipation at high spatial resolution is estimated using image sequences acquired with a land-based X-band marine radar. Using the radar intensity data, transformed to normalized radar cross section σ0, the temporal and spatial distributions of wave breaking are identified using a threshold developed via the data probability density function. In addition, the inlet bathymetry is determined via depth inversion of the radar-derived frequencies and wavenumbers of the surface waves using a preexisting algorithm (cBathy). Wave height transformation is calculated through the 1D cross-shore energy flux equation incorporating the radar-estimated breaking distribution and bathymetry. The accuracy of the methodology is tested by comparison with in situ wave height observations over a 9-day period, obtaining correlation values R = 0.68 to 0.96, and root-mean-square errors from 0.05 to 0.19 m. Predicted wave forcing, computed as the along-inlet gradient of the cross-shore radiation stress was onshore during high-wave conditions, in good agreement (R = 0.95) with observations.

scholarly journals A MODEL IN FREQUENCY DOMAIN FOR TRANSFORMATION OF FULLY DISPERSIVE NONLINEAR WAVES

2018 ◽  
pp. 60
Author(s):  
Samira Ardani ◽  
James M. Kaihatu
Keyword(s):  
Frequency Domain ◽  
Evolution Equations ◽  
Wave Model ◽  
Multiple Scale ◽  
Transformation Model ◽  
Wave Transformation ◽  
Numerical Verification ◽  
Resonant Interactions ◽  
Dispersive Model ◽  
Mathematical Derivation

In this study, mathematical derivation and numerical verification of a wave transformation model in frequency domain is discussed. This wave model is fully dispersive and nonlinear; and is derived based on the WKB assumptions. Transforming the problem into the frequency domain and using multiple scale analysis in space and perturbation theory, the model is expanded up to second order in wave steepness. This fully dispersive nonlinear wave model is a set of evolution equations which explicitly contains quadratic near-resonant interactions. The comparison between the presented model, the existing fully dispersive model and a nearshore model with different set of laboratory and field data shows that the presented model provides significant improvements particularly at higher frequencies.

scholarly journals A LABORATORY AND FIELD STUDY ON 2DH SPECTRAL WAVE TRANSFORMATION IN MUDDY ENVIRONMENTS

2012 ◽  
Vol 1 (33) ◽  
pp. 39
Author(s):  
Mohsen Soltanpour ◽  
S. Abbas Haghshenas ◽  
Tomoya Shibayama
Keyword(s):  
Wave Spectrum ◽  
Field Measurements ◽  
Wave Model ◽  
Transformation Model ◽  
Wave Transformation ◽  
S Wave ◽  
North West ◽  
The North ◽  
Wave Basin ◽  
The Persian Gulf

The present paper offers a set of wave basin experiments on muddy beds together with field measurements data at Hendijan Mud Coast in the north-west corner of the Persian Gulf in order to investigate the 2DH spectral wave transformation over muddy beds. A dissipation model was added to REF/DIF S wave model to develop a numerical wave spectrum transformation model for muddy beaches. The proposed model was utilized to analyze the experimental and field measurements data on muddy beds. The simulated wave spectra over-mud bed are in fair agreement with the measurements.

scholarly journals A NUMERICAL MODEL OF NEARSHORE CURRENTS DUE TO IRREGULAR WAVES

1988 ◽  
Vol 1 (21) ◽  
pp. 83 ◽  
Author(s):  
Masataka Yamaguchi
Keyword(s):  
Numerical Model ◽  
Water Level ◽  
Wave Height ◽  
Wave Model ◽  
Irregular Waves ◽  
Wave Transformation ◽  
Level Variation ◽  
Water Level Variation ◽  
Mean Water Level ◽  
Nearshore Currents

This paper presents a numerical model of nearshore currents due to irregular waves. The radiation stress is estimated by a current-depth refraction model for irregular waves, in which the energy dissipation due to wave breaking is modeled through the use of a saturated frequency spectrum in shallow water. The model is in reasonable agreement with measured wave height, mean water level variation and observed nearshore current patterns. Next, the model is applied to the computation of wave transformation and nearshore currents on a uniformly sloping beach and on model topographies with complicated contour lines. Comparison with the results based on a regular wave model shows that wave irregularity has a smoothing effect on cross-shore distributions of wave height, mean water level variation and longshore currents, but that it does not have much effect on nearshore current patterns.

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