scholarly journals MODELLING WAVE INTERFERENCE PATTERNS USING THE SWAN MODEL

2018 ◽  
pp. 42
Author(s):  
Gal Akrish ◽  
Pieter Smit ◽  
Marcel Zijlema ◽  
Ad Reniers
Keyword(s):  
Transport Processes ◽  
Spectral Space ◽  
Wave Statistics ◽  
Wave Interference ◽  
Rapid Changes ◽  
Wave Heights ◽  
Wave Trains ◽  
Wave Models ◽  
Coastal Inlets ◽  
Mutually Independent

This study presents an efficient approach of resolving wave interference patterns in spectral wave models (e.g., SWAN). Such interference patterns, which frequently occur in coastal waters (e.g., near headlands, harbor entrances and coastal inlets), may lead to rapid changes in wave statistics, and thus, can affect wave-driven flow and transport processes. Therefore, prediction of wave conditions for coastal applications should account for these effects. Presently, operational wave models compute the mean wave properties by solving the action balance equation, which describes the transport of wave energy through geographic and spectral space, augmented with source terms to account for non-conservative and nonlinear processes. This model equation, initially intended for deep water conditions, is derived under the assumption that waves propagating at angles are mutually independent so that the wave field changes its mean properties (e.g. wave height) over many wavelengths. However in nearshore areas, the interaction of waves with variable bathymetry and currents can result in interference zones where crossing wave trains are statistically correlated and wave heights change rapidly.

scholarly journals Stochastic Modeling of Coherent Wave Fields over Variable Depth

2015 ◽  
Vol 45 (4) ◽  
pp. 1139-1154 ◽  
Author(s):  
P. B. Smit ◽  
T. T. Janssen ◽  
T. H. C. Herbers
Keyword(s):  
Transport Equation ◽  
Deterministic Model ◽  
Laboratory Data ◽  
Radiative Transport ◽  
Wave Statistics ◽  
Wave Interference ◽  
Coherent Wave ◽  
Homogeneous Wave ◽  
Radiative Transport Equation ◽  
Wave Models

AbstractRefractive focusing of swell waves can result in fast-scale variations in the wave statistics because of wave interference, which cannot be resolved by stochastic wave models based on the radiative transport equation. Quasi-coherent statistical theory does account for such statistical interferences and the associated wave inhomogeneities, but the theory has thus far been presented in a form that appears incompatible with models based on the radiative transfer equation (RTE). Moreover, the quasi-coherent theory has never been tested against field data, and it is not clear how the coherent information inherent to such models can be used for better understanding coastal wave and circulation dynamics. This study therefore revisits the derivation of quasi-coherent theory to formulate it into a radiative transport equation with a forcing term that accounts for the inhomogeneous part of the wave field. This paper shows how the model can be nested within (or otherwise used in conjunction with) quasi-homogeneous wave models based on the RTE. Through comparison to laboratory data, numerical simulations of a deterministic model, and field observations of waves propagating over a nearshore canyon head, the predictive capability of the model is validated. The authors discuss the interference patterns predicted by the model through evaluation of a complex cross-correlation function and highlight the differences with quasi-homogeneous predictions. These results show that quasi-coherent theory can extend models based on the RTE to resolve coherent interference patterns and standing wave features in coastal areas, which are believed to be important in nearshore circulation and sediment transport.

scholarly journals Comprehensive Wind and Wave Statistics and Extreme Values for Design and Analysis of Marine Structures in the Adriatic Sea

2021 ◽  
Vol 9 (5) ◽  
pp. 522
Author(s):  
Marko Katalinić ◽  
Joško Parunov
Keyword(s):  
Adriatic Sea ◽  
Extreme Values ◽  
Wave Climate ◽  
Offshore Structures ◽  
Model Parameters ◽  
Peak Period ◽  
Significant Wave ◽  
Wave Statistics ◽  
Wave Heights ◽  
Almost All

Wind and waves present the main causes of environmental loading on seagoing ships and offshore structures. Thus, its detailed understanding can improve the design and maintenance of these structures. Wind and wave statistical models are developed based on the WorldWaves database for the Adriatic Sea: for the entire Adriatic Sea as a whole, divided into three regions and for 39 uniformly spaced locations across the offshore Adriatic. Model parameters are fitted and presented for each case, following the conditional modelling approach, i.e., the marginal distribution of significant wave height and conditional distribution of peak period and wind speed. Extreme significant wave heights were evaluated for 20-, 50- and 100-year return periods. The presented data provide a consistent and comprehensive description of metocean (wind and wave) climate in the Adriatic Sea that can serve as input for almost all kind of analyses of ships and offshore structures.

An Experimental Study of Shallow Water Wave Statistics on Mild Bed Slopes

2011 ◽  
Author(s):  
Vasiliki Katsardi ◽  
Chris Swan
Keyword(s):  
Water Depth ◽  
Measured Data ◽  
Intermediate Water ◽  
Statistical Distributions ◽  
Spectral Bandwidth ◽  
Peak Period ◽  
Wave Statistics ◽  
Wave Heights ◽  
Bed Slope ◽  
Water Depths

This paper describes a new series of laboratory observations, undertaken in a purpose built wave flume, in which a number of scaled simulations of realistic ocean spectra were allowed to evolve over a range of mild bed slopes. The purpose of the study was to examine the distribution of wave heights and its dependence on the local water depth, d, the local bed slope, m, and the nature of the input spectrum; the latter considering variations in the spectral peak period, Tp, the spectral bandwidth and the wave steepness. The results of the study show that for mild bed slopes the statistical distributions of wave heights are effectively independent of both the bed slope and the spectral bandwidth. However, the peak period plays a very significant role in the sense that it alters the effective water depth. Following detailed comparisons with the measured data, the statistical distributions for wave heights in relatively deep water are found to be in reasonable agreement with the Forristall [1] and Glukhovskii [2] distributions. For intermediate water depths, the Battjes & Groenendijk [3] distribution works very well. However, for the shallowest water depths none of the existing distributions provides good agreement with the measured data; all leading to an over-estimate of the largest wave heights.

Statistics of Wave Crests From Models vs. Measurements

2002 ◽  
Author(s):  
Marc Prevosto ◽  
Geoerge Z. Forristall
Keyword(s):  
Parametric Models ◽  
Wave Crest ◽  
Wave Statistics ◽  
Irregular Wave ◽  
Analysis Phase ◽  
Main Emphasis ◽  
Wave Models ◽  
Intercomparison Study ◽  
Crest Height

The analysis phase of the Wave Crest Sensor Intercomparison Study (WACSIS) focussed on the interpretation of the wave data collected by the project during the winter of 1997–98. Many aspects of wave statistics have been studied, but the main emphasis has been on crest height distributions, and recommendations for crest heights to be used in air gap calculations. In this paper we first describe comparisons of the crest height distributions derived from the sensors (radars, wave staffs, laser) and from simulations based on 3D second order irregular wave models. These comparisons permit us to make conclusions on the quality of these models and to qualify the ability of some sensors to measure the crest heights accurately. In the second part two new parametric models of the crest height distributions are discussed and their superiority to standard parametric models is demonstrated.

Studies of Extreme Energy Localizations With Smoothed Particle Hydrodynamics

2015 ◽  
Author(s):  
Ayan Moitra ◽  
Christopher Chabalko ◽  
Balakumar Balachandran
Keyword(s):  
Smoothed Particle Hydrodynamics ◽  
Ocean Waves ◽  
Breaking Wave ◽  
Wave Focusing ◽  
Wave Interference ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
Wave Heights ◽  
The Waves ◽  
Wave Phenomena

Smoothed particle hydrodynamics (SPH) is used to simulate hydrodynamic waves and wave phenomena including focusing from wave interference. This Lagrangian based method can be used to naturally simulate hydrodynamic free surfaces, including the free surface of a breaking wave. A virtual wave tank is simulated where wave motions can be excited from either side. Wave focusing is observed at the tank center, where the waves interfere. As a measure of the interference, the wave heights that result from focusing are presented. Certain types of wave focusing are thought to lead to large ocean waves. The efficacy of SPH in modeling wave focusing is critical to further understanding and predicting extreme wave phenomena with SPH.

Non-Linear Calculation of Tailored Wave Trains for Experimental Investigation of Extreme Structure Behaviour

2004 ◽  
Author(s):  
Gu¨nther F. Clauss ◽  
Janou Hennig ◽  
Christian E. Schmittner ◽  
Walter L. Ku¨hnlein
Keyword(s):  
Experimental Investigation ◽  
Wave Propagation ◽  
Wave Structure ◽  
Linear Wave ◽  
Advantages And Disadvantages ◽  
Non Linear ◽  
Linear Wave Propagation ◽  
Precise Prediction ◽  
Wave Trains ◽  
Wave Models

The experimental investigation of extreme wave/structure interaction scenarios puts high demands on wave generation and calculation. This paper presents different approaches for modelling non-linear wave propagation. Results of numerical simulations from two different numerical wave tanks are compared to models tests. A further approach uses analytical wave models which are combined with empirical terms to allow a fast and precise prediction of non-linear wave propagation for day-to-day use. All approaches can be used either separately or in combination — depending on their particular purpose. As an application, different special wave scenarios — both academic and realistic — are generated and validated by measurements. The advantages and disadvantages of the presented methods are discussed in detail with regard to their appropriate use for investigations of extreme structure behaviour.

scholarly journals MEASUREMENT OF INCIDENT WAVE HEIGHT IN COMPOSITE WAVE TRAINS

1974 ◽  
Vol 1 (14) ◽  
pp. 21
Author(s):  
Ake Sandstrom
Keyword(s):  
Wave Height ◽  
Incident Wave ◽  
Wave Train ◽  
Wave Length ◽  
Wave Theory ◽  
Arithmetic Mean ◽  
Reflected Waves ◽  
Wave Heights ◽  
Wave Trains ◽  
Composite Wave

A method is proposed for measurement of the incident wave height in a composite wave train. The composite wave train is assumed to consist of a superposition of regular incident and reflected waves with the same wave period. An approximate value of the incident wave height is obtained as the arithmetic mean of the wave heights measured "by two gauges separated a quarter of a wave length. The accuracy of the method in relation to the location of the gauges and the wave parameters is investigated using linear and second order wave theory. Results of the calculations are presented in diagrams.

scholarly journals WAVE STATISTICS ALONG THE NORTHERN COAST OF EGYPT

1974 ◽  
Vol 1 (14) ◽  
pp. 5
Author(s):  
M. Manohar ◽  
I.E. Mobarek ◽  
A. Morcos ◽  
H. Rahal
Keyword(s):  
Nile Delta ◽  
Spectral Band ◽  
Northern Coast ◽  
Wave Statistics ◽  
Wave Measurements ◽  
Narrow Spectral Band ◽  
Wave Heights ◽  
Significant Wave Heights ◽  
Nile Delta Coast ◽  
Comprehensive Study

As a forerunner of a comprehensive study of wave and energy climate of the Nile Delta coast covering a period of more than 50 years, wave measurements taken in 3 locations along the coast in the year 1972 were statistically analysed. Shortcut methods based on statistical approach were used to analyse the wave records enabling quicker analysis. Spectral analysis of the wave records indicates narrow spectral band similar to Raleigh distribution. The histograms and frequency distribution curves of significant wave heights, and the relationships between various statistical prarameters such as H , H,,,„, H,,„ and H also max 1/10' 1/3 rms agree closely with Raleigh distribution curves and parameters enabling the use of Raleigh distribution function in subsequent studies. Finally since the wave characteristics and wave energy climates are most important in the analysis of coastline changes, they are drawn from the data obtained from the analysis.

scholarly journals Comparison of Design Wave Heights Determined on the Basis of Long- and Short-term Measurement Data

2018 ◽  
Vol 65 (2) ◽  
pp. 123-142
Author(s):  
Marek Szmytkiewicz ◽  
Piotr Szmytkiewicz ◽  
Tomasz Marcinkowski
Keyword(s):  
Measurement Data ◽  
Research Station ◽  
Short Term ◽  
Wave Data ◽  
Wave Parameters ◽  
Wave Heights ◽  
Short And Long Term ◽  
Wave Trains ◽  
Coastal Research

AbstractThe objective of this study is to determine differences between design wave heights determined on the basis of short- and long-term wave trains. Wave parameters measured over a period of 7.47 years in the vicinity of Coastal Research Station Lubiatowo were used as short-term wave data, while wave parameters determined through the so-called wave reconstruction for a period of 44 years for the same region and depth were used as long-term wave data. The results of the calculations lead to the conclusions the significant wave height distributions obtained for short and long-term wave data are similar.

Physics-Based Approach to Wave Statistics and Probability

2013 ◽  
Author(s):  
Alexander V. Babanin
Keyword(s):  
Extreme Events ◽  
Modulational Instability ◽  
Probability Distributions ◽  
Rayleigh Distribution ◽  
Order Theory ◽  
Second Order ◽  
Ocean Engineering ◽  
Actual Distribution ◽  
Wave Statistics ◽  
Wave Heights

Design criteria in ocean engineering, whether this is one in 50 years or one in 5000 years event, are hardly ever based on measurements, and rather on statistical distributions of relevant metocean properties. Of utmost interest is the tail of these distributions, that is rare events such as the highest waves with low probability. Engineers have long since realised that the superposition of linear waves with narrow-banded spectrum as depicted by the Rayleigh distribution underestimates the probability of extreme wave crests, and is not adequate for wave heights either, which is a critical shortcoming as far as the engineering design is concerned. Ongoing theoretical and experimental efforts have been under way for decades to address this issue. Here, we will concentrate on short-term statistics, i.e. probability of crests/heights of individual waves. Typical approach is to treat all possible waves in the ocean or at a particular location as a single ensemble for which some comprehensive solution can be found. The oceanographic knowledge, however, now indicates that no single and united comprehensive solution is possible. Probability distributions in different physical circumstances should be different, and by combining them together the inevitable scatter is introduced. The scatter and the accuracy will not improve by increasing the bulk data quality and quantity, and it hides the actual distribution of extreme events. The groups have to be separated and their probability distributions treated individually. The paper offers a review of physical conditions, from simple one-dimensional trains of free waves to realistic two-dimensional wind-forced wave fields, in order to understand where different probability distributions can be expected. If the wave trains/fields in the wave records are stable, distributions for the second-order waves should serve well. If modulational instability is active, rare extreme events not predicted by the second-order theory should become possible. This depends on wave steepness, bandwidth and directionality. Mean steepness also defines the wave breaking and therefore the upper limit for wave heights in this group of conditions. Under hurricane-like circumstances, the instability gives way to direct wind forcing, and yet another statistics is to be expected.

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