Climatologically Modeled Wave Field Analyses in the Western South Atlantic

2009 ◽  
Author(s):  
Eric Oliveira Ribeiro ◽  
Marcelo Andrioni ◽  
Renato Parkinson Martins ◽  
Guisela Grossmann Matheson ◽  
Jose´ Henrique Alves ◽  
...  
Keyword(s):  
High Pressure ◽  
Wave Field ◽  
Wave Height ◽  
Extreme Values ◽  
South Atlantic ◽  
Structure Design ◽  
Plant Design ◽  
Wave Direction ◽  
Pressure Center ◽  
Predominant Direction

Wave height, period and direction are basic parameters for designing off-shore structures. Besides this direct application, knowledge of the regional characteristics of a wave field can also help in the selection of optimal regions for wave power energy plant design and installation. A wave climatology based on data generated by a WAVEWATCH III model simulation (NOAA WW3) for the Brazilian coast was analyzed and validated against statistical values derived from opportunity vessel measurements. The hindcast covered the period from January 1997 to December 2005 in a region between 5°N – 40°S and 10°W – 65°W. The grid used was uniform with a 0.25° spacial resolution. The boundary conditions were obtained from NOAA WW3 operational model and the atmospheric forcing from NOAA GFS model. The model results were calibrated with field data and detailed information about the simulation can be obtained in Alves et al. (2008) and Alves et al. (in press). Monthly averages of significant height, period and wavelength were calculated using 3 hour time resolution fields. Since a simple mean direction has small physical representativeness, the predominant direction (moda) and associated persistency were obtained from the data. The results were then compared with values from the U.S. Navy Marine Climate Atlas of the World. This Atlas has four points located within the selected model grid region. These points showed good agreement with wave period, height and direction persistency based on the WW3 simulation results. The wave climatology showed that the predominant wave direction from April to July was from S and SE in southern Brazil, associated with swells related to cold fronts. The S and SE swells were also responsible for the largest mean wave height (2.1 m) observed in the climatology. Another result that was validated with the literature was the E and NE predominant wave direction during the austral summer. This phenomenon is associated with winds originated from the South Atlantic High Pressure Center, which is a semi permanent high pressure center near Trindade Island. The wave climate in northern Brazil showed a predominant direction from the N during January to March, associated with the northern hemisphere winter storms. During the remaining months of the year, the predominant wave direction is E and NE associated with trade winds. The model results are still in a processing phase to produce extreme values, which will be more useful for coastal and off-shore structure design.

Optimization of Segmented Wave-Maker Control to Generate Spatially Uniform Regular Waves in a Rounded-Rectangular Wave Basin

2021 ◽  
Author(s):  
Daichi Ota ◽  
Hidetaka Houtani ◽  
Hiroshi Sawada ◽  
Harukuni Taguchi
Keyword(s):  
Wave Field ◽  
Wave Height ◽  
Simulated Annealing Algorithm ◽  
Optimal Solution ◽  
Optimization Method ◽  
Linear Wave ◽  
Wave Direction ◽  
Wave Basin ◽  
Test Zone ◽  
Wave Maker

Abstract A wave field in a wave basin inevitably has spatial variation due to the wave’s cylindrical propagation property. Therefore, we aimed to develop an optimization method for the control of wave-makers to produce a spatially uniform wave field in a specified test zone inside a wave basin with an arbitrary arrangement of wave-makers. The optimization is based on the simulated annealing algorithm, a method for finding a globally optimal solution, which was combined with a numerical wave basin based on linear wave-maker theory. A wave generation experiment was performed in the actual sea model basin (80 m long, 40 m wide, and 4.5 m deep) at the National Maritime Research Institute to validate the proposed optimization method. A case study was conducted with a long-crested regular-wave with a wave height of 10 cm, wavelength of 4.0 m, and wave direction of 180 degrees, which corresponds to the longitudinal direction of the wave basin. A 40-m × 14-m test zone was set in the middle of the wave basin. The experimental results with and without the proposed optimization were compared, which confirmed that the spatial uniformity of the wave field was improved, and the coefficient of variation for the wave height in the test zone decreased from 0.127 to 0.029.

scholarly journals Directional Extreme Value Models in Wave Energy Applications

Atmosphere ◽  
2020 ◽  
Vol 11 (3) ◽  
pp. 274
Author(s):  
Flora Karathanasi ◽  
Takvor Soukissian ◽  
Kostas Belibassakis
Keyword(s):  
Wave Height ◽  
Wave Energy ◽  
Extreme Values ◽  
Extreme Value ◽  
Fourier Series Expansion ◽  
Accurate Estimation ◽  
Wave Direction ◽  
Extreme Wave ◽  
Energy Applications ◽  
Wide Range

A wide range of wave energy applications relies on the accurate estimation of extreme wave conditions, while some of them are frequently affected by directionality. For example, attenuators and terminators are the most common types of wave energy converters whose performance is highly influenced by their orientation with respect to the prevailing wave direction. In this work, four locations in the eastern Mediterranean Sea are selected with relatively high wave energy flux values and extreme wave heights are examined with wave direction as a covariate. The Generalized Pareto distribution is used to model the extreme values of wave height over a pre-defined threshold, with its parameters being expressed as a function of wave direction through Fourier series expansion. In order to be consistent with the analysis obtained from the independent fits for directional sectors, the estimation of parameters is based on a penalized maximum likelihood criterion that ensures a good agreement between the two approaches. The obtained results validate the integration of directionality in extreme value models for the examined locations and design values of significant wave height are provided with respect to direction for the 50- and 100-year return period with bootstrap confidence intervals.

scholarly journals ÁP DỤNG MÔ HÌNH SWAN DỰ BÁO TRƯỜNG SÓNG VEN BỜ BIỂN HẢI PHÒNG

2019 ◽  
Vol 19 (1) ◽  
pp. 41-48
Author(s):  
Le Duc Cuong
Keyword(s):  
Wave Field ◽  
Wave Height ◽  
Coastal Area ◽  
Rainy Season ◽  
Dry Season ◽  
Maximum Height ◽  
Wave Direction ◽  
Swan Model ◽  
Dominant Wave ◽  
Near Shore

This paper presents some results of studying the SWAN model, and application of SWAN model to simulate wave field representative of the rainy season and dry season in the coastal area of Hai Phong. During the dry season, the dominant wave direction is in a range from 60o to 100o, maximum height of waves near shore is in a range from 1,0 m to 1,5 m with wavelength of about 2,0 m to 5,0 m, maximum height of waves offshore is in a range from 2,0 m to 2,5 m with wavelength of about 6,0 m to 16 m. During the rainy season, wave height near shore is in a range from 0,2 m to 0,6 m, and that offshore is in a range from 0,8 m to 1,4 m, maximum height of waves is about 3,4 m, predominant wave directions in this season are E, SE and S. In this scenario that predicts waves generated by storms, wave height offshore is in a range from 8,0 m to 10 m with wavelength of about 60 m, and that near shore is in a range from 2,0 m to 4,0 m with wavelength of about 10–20 m.

The Concept of the Optimum Alignment of Discharge Pipelines Due to the Minimization of the Wave Forces

1992 ◽  
Vol 25 (9) ◽  
pp. 211-216
Author(s):  
A. Akyarli ◽  
Y. Arisoy
Keyword(s):  
Wave Height ◽  
Wave Force ◽  
Wave Forces ◽  
Wave Direction ◽  
Incoming Wave ◽  
Pipeline Route ◽  
Optimum Alignment ◽  
The Cost ◽  
Resultant Wave

As the wave forces are the function of the wave height, period and the angle between the incoming wave direction and the axis of the discharge pipeline, the resultant wave force is directly related to the alignment of the pipeline. In this paper, a method is explained to determine an optimum pipeline route for which the resultant wave force becomes minimum and hence, the cost of the constructive measures may decrease. Also, the application of this method is submitted through a case study.

Application of Wave Devouring Propulsion System for Ocean Engineering

2013 ◽  
Author(s):  
Yutaka Terao ◽  
Norimitsu Sakagami
Keyword(s):  
Data Acquisition ◽  
Wave Height ◽  
Autonomous Navigation ◽  
Data Acquisition System ◽  
Propulsion System ◽  
Acquisition System ◽  
Wave Power ◽  
Wave Direction ◽  
Ocean Engineering ◽  
Damping Force

A Wave Devouring Propulsion System (WDPS) generates thrust directly from wave power while simultaneously generating a strong damping force. A simple WDPS design consists of hydrofoils mounted below the bow of a vessel. If a WDPS is integrated with the hull of a vessel, then it can power the vessel forward, even against the wave direction itself. One example of a successful WDPS was installed on the vessel named Mermaid II, which completed a trans-Pacific voyage in 2008, traveling approximately 7,800 km from Hawaii to Japan using wave power alone. This success indicates that the WDPS has potential for use in the field of ocean engineering. As described in this paper, we intend to apply the WDPS to the small autonomous boat and to conduct sea trials. We designed and built an autonomous WDPS boat, developed a data acquisition system, and experimentally investigated its performance in Orida Bay. The experimentally obtained results indicate that the autonomous navigation of the WDPS boat is possible when the wave height is greater than 5–10 cm.

scholarly journals FUTURE CHANGES IN SPECTRAL WAVE CLIMATE AROUND JAPAN UNDER GLOBAL WARMING

2020 ◽  
pp. 10
Author(s):  
Tomoya Shimura ◽  
Nobuhito Mori
Keyword(s):  
Global Warming ◽  
Wave Height ◽  
Climate Change Impacts ◽  
Wave Climate ◽  
Structure Design ◽  
Future Projections ◽  
Wave Statistics ◽  
The Mean ◽  
Ocean Wave Climate ◽  
East Asia Region

Future projections of ocean wave climate related with global warming has been conducted for the assessment of climate change impacts on coastal disaster, beach morphology, and coastal structure design. In this study, we conduct the high-resolution future wave climate projection in the East Asia region and detail analysis on wave climate based on two-dimensional wave spectra in addition to conventional wave statistics (significant wave height). Future changes in wave height, period and direction can be discussed consistently owing to analysis on the mean wave spectra.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/FEYPZFRr5SQ

Consideration of Epistemic Uncertainty in Extreme Wave Height Estimation

2014 ◽  
Author(s):  
Ryota Wada ◽  
Takuji Waseda
Keyword(s):  
Gulf Of Mexico ◽  
Observational Data ◽  
Wave Height ◽  
Extreme Values ◽  
Epistemic Uncertainty ◽  
Extreme Value Distribution ◽  
Predictive Distribution ◽  
Extreme Value ◽  
Posterior Predictive Distribution ◽  
Value Estimation

Extreme value estimation of significant wave height is essential for designing robust and economically efficient ocean structures. But in most cases, the duration of observational wave data is not efficient to make a precise estimation of the extreme value for the desired period. When we focus on hurricane dominated oceans, the situation gets worse. The uncertainty of the extreme value estimation is the main topic of this paper. We use Likelihood-Weighted Method (LWM), a method that can quantify the uncertainty of extreme value estimation in terms of aleatory and epistemic uncertainty. We considered the extreme values of hurricane-dominated regions such as Japan and Gulf of Mexico. Though observational data is available for more than 30 years in Gulf of Mexico, the epistemic uncertainty for 100-year return period value is notably large. Extreme value estimation from 10-year duration of observational data, which is a typical case in Japan, gave a Coefficient of Variance of 43%. This may have impact on the design rules of ocean structures. Also, the consideration of epistemic uncertainty gives rational explanation for the past extreme events, which were considered as abnormal. Expected Extreme Value distribution (EEV), which is the posterior predictive distribution, defined better extreme values considering the epistemic uncertainty.

Pressure and Winds

2000 ◽  
Author(s):  
C. David Whiteman
Keyword(s):  
High Pressure ◽  
Pressure Gradient ◽  
Pressure Difference ◽  
Low Pressure ◽  
Pressure Center ◽  
Vertical Column ◽  
Wind Speeds ◽  
Weather Observations ◽  
Stormy Weather ◽  
Rotation Of The Earth

Atmospheric pressure at a given point in the atmosphere is the weight of a vertical column of air above that level. Differences in pressure from one location to another cause both horizontal motions (winds) and vertical motions (convection and subsidence) in the atmosphere. Vertical motions, whether associated with high and low pressure centers or with other meteorological processes, are the most important motions for producing weather because they determine whether clouds and precipitation form or dissipate. The location of high and low pressure centers is a key feature on weather maps, providing information about wind direction, wind speed, cloud cover, and precipitation. Pressure-driven winds carry air from areas where pressure is high to areas where pressure is low. However, the winds do not blow directly from a high pressure center to a low pressure center. Because of the effects of the rotation of the earth and friction, winds blow clockwise out of a high pressure center and counterclockwise into a low pressure center in the Northern Hemisphere. These wind directions are reversed in the Southern Hemisphere. The strength of the wind is proportional to the pressure difference between the two regions. When the pressure difference or pressure gradient is strong, wind speeds are high; when the pressure gradient is weak, wind speeds are low. As air flows out of a high pressure center, air from higher in the atmosphere sinks to replace it. This subsidence produces warming and the dissipation of clouds and precipitation. As air converges in a low pressure center, it rises and cools. If the air is sufficiently moist, cooling can cause the moisture to condense and form clouds. Further lifting of the air can produce precipitation. Thus, rising pressure readings at a given location indicate the approach of a high pressure center and fair weather, whereas falling pressure readings indicate the approach of a low pressure center and stormy weather. The vertical motions caused by the divergence of air out of a high pressure center or the convergence of air into a low pressure center are generally weak, with air rising or sinking at a rate of several cm per second, and they cannot be measured by routine weather observations.

scholarly journals Pemanfaatan Data Angin Untuk Karakteristik Gelombang Laut Di Perairan Natuna Berdasarkan Data Angin tahun 2009 - 2018

2019 ◽  
Vol 8 (2) ◽  
pp. 55
Author(s):  
Ary Afriady ◽  
Tasdik Mustika Alam ◽  
Mochamad Furqon Mustika Azis Ismail
Keyword(s):  
Wave Height ◽  
Wave Period ◽  
Wind Data ◽  
Wave Direction ◽  
The West ◽  
Maximum Wave Height ◽  
Transition Season ◽  
Forecasting Analysis ◽  
Environmental Prediction ◽  
Wave Forecasting

Analisis data angin dilakukan untuk meramalkan dan menentukan karakteristik gelombang laut di perairan Pulau Natuna. Data angin yang digunakan dalam penelitian ini berasal dari National Centers for Environmental Prediction (NCEP) selama 10 tahun dari tahun 2009 sampai dengan tahun 2018. Metoda yang digunakan untuk estimasi tinggi, periode dan arah gelombang laut yang dibangkitkan oleh angin adalah metode Svedrup, Munk dan Bretschneider (SMB). Hasil perhitungan peramalan karakteristik gelombang diperoleh bahwa pembentukan gelombang didominasi oleh arah yang berasal dari timur laut dan terjadi pada musim barat dan musim peralihan 1. Adapun pada musim timur dan peralihan, arah dominan gelombang masing-masing berasal dari selatan dan barat daya. Tinggi gelombang maksimum 1,0-1,4 m sering terjadi pada musim musim timur, adapun tinggi gelombang minimum 0,2-0,6 m dominan terjadi pada musim musim peralihan. Periode gelombang dominan ditemukan pada kisaran 7-9 detik yang terjadi pada tiap musim.  The analysis of wind data has been done to forecast and determine the characteristic of the ocean wave in Natuna Island waters. The wind data in this study came from the National Centers for Environmental Prediction (NCEP) for a period of 10 years from 2009 to 2018. The method to estimate wave height, wave period, and wave direction generated by wind is Sverdrup, Munk dan Bretschneider (SMB) system. The results of wave forecasting analysis show that the formation of the wave is mainly originated from the northeast which occurs during the west and first transition season. As for the east and second transition season, the origin of wave formation coming from the south and southwest, respectively. The maximum wave height of 1.0-1.4 m frequently occurs during the east monsoon, while the minimum wave height. The dominant wave period is found in the range of 7-9 seconds, which occurs in every season. 

Tow Forces for Emergency Towing of Containerships

2015 ◽  
Vol 137 (5) ◽  
Author(s):  
Vladimir Shigunov ◽  
Thomas E. Schellin
Keyword(s):  
Wave Height ◽  
Current Speed ◽  
Sea Waves ◽  
Wave Direction ◽  
Equilibrium Equations ◽  
Significant Wave ◽  
Wind Speeds ◽  
Time Average ◽  
Wave Drift Forces ◽  
Drift Forces

For a series of five containerships of differing capacities (707, 3400, 5300, 14,000, and 18,000 TEU), systematic computations were performed to estimate the tow force required in an emergency. Time-average ship positions with respect to the given waves, wind, and current directions and the corresponding time-average forces were considered. Current speed was considered to include also towing speed. Directionally aligned as well as not aligned wind and waves were investigated. Wave height, wind speed, and wave and wind direction relative to current direction were systematically varied. Wind speeds based on the Beaufort wind force scale corresponded to significant wave heights for a fully arisen sea. Waves were assumed to be irregular short-crested seaways described by a Joint North Sea Wave Observation Project (JONSWAP) spectrum with peak parameter 3.3 and cosine squared directional spreading. For each combination of current speed, wave direction, significant wave height, and peak wave period, the required tow force and the associated drift angle were calculated. Tow force calculations were based on the solution of equilibrium equations in the horizontal plane. A Reynolds-Averaged Navier–Stokes (RANS) solver obtained current and wind forces and moments; and a Rankine source-patch method, drift forces and moments in waves. Tow forces accounted for steady (calm-water) hydrodynamic forces and moments, constant wind forces and moments, and time-average wave drift forces and moments. Rudder and propeller forces and towline forces were neglected.

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