Characteristics Of Wind Waves Research Articles

Математическое моделирование волнового режима бухты Ай-Тодор

Investigation of wave regime of coastal water areas is practically important for safe shipping, constructing and using of coastal infrastructure objects. At the present paper statistical characteristics and space distribution of parameters of wind waves in the Ay-Todor Bay region placed on the Crimea South Coast of the Black Sea are obtained on the basis of mathematical simulation. Analysis of the wind wave parameters for the year diapason of 1979–2017 has shown that waves running from the east and having 0.5 m heights and 3.0–3.5 s mean periods are the most repeatable. The most durable storms are formed by waves coming from East–South-South-West sector in the period from December to January. The multiannual calm duration is equal to ~11 days. Estimation of extremal characteristics (height, period and length) of wind waves of different probability, which possible one time in a year, 5, 10, 25, 50 and 100 years are made. For the storm probable one time in 25 years the mean wave height near the boundary of the Ay-Todor Bay is equal to 4.5 m. For this storm the wave height of 1% probability reaches 9.6 m. For the directions of winds of 4 % regime probability which causes the most dangerous waves calculations of wave characteristics with high space resolution (~1.5 m) are carried out by using of SWAN model and nested grid technology. Fields of significant wave height, mean wave length, bottom wave orbital velocities and space distribution of wave breaking zones are analyzed. It is found that most intensive waves are generated by wind having south-east, east and south directions. Maximal bottom orbital velocities of wave current reaches of 2.5–3.5 m/s and occurs along the coast till 10 m depth. Model calculation of wave currents by using of SWASH model allowed obtained presence in the coastal zone near beach of local cyclonic eddy, which transport suspended sediments along its south edge from beach towards the sea.

Development law of lateral displacement of deep soil mass in submerged breakwater

The 12.5m deep water channel project under Nanjing of the Yangtze River is a national key project. Based on the hechangzhou waterway section of the project, combined with the characteristics of water depth, strong wind, rapid flow and high wave, aiming at the problems such as short construction time, difficult instrument embedding, easy damage and low data collection efficiency, field monitoring test is carried out to monitor the foundation of submerged dike structure in the construction process The lateral displacement of deep soil mass, clear its development law, provide a strong guarantee for safe construction.

Local Katabatic Winds of the Russian Federation and Their Observation Using Synthetic Aperture Radar Imagery

Data from synthetic aperture radars (SAR) provide new opportunities for observing and studying local katabatic winds (bora and foehn) over the seas in different regions of the Russian Federation and adjacent marine basins. The impact of these winds on the characteristics of small-scale wind waves leads to the formation of characteristic manifestations on the sea surface, which in turn can be seen in SAR images. Satellite SAR data, unlike subsatellite observations, make it possible to see the phenomena in coastal zones and large lakes, estimate their spatial scales, and determine a number of quantitative characteristics. The analysis of the collected SAR images shows that bora-like and foehn-like local winds have similar characteristics and cover vast areas of the inland and marginal seas of the Russian Federation. The similarity of the manifestations of local winds clearly indicates the same physical and aerohydrodynamic mechanisms of their onset and display on SAR images. It is shown that spaceborne SAR data, which are 2D patterns of the ‘frozen wind’, are extremely useful for studying and monitoring local winds over the seas, especially where the network of weather stations is extremely sparse.

Wind-waves in the coast of mainland Portugal induced by post-tropical storms

In this short communication paper, we investigate the characteristics of wind-waves in Portugal mainland coast induced by post-tropical storms. Six major Atlantic hurricane events that occurred between 2012 and 2019 are studied: Rafael (2012), Joaquin (2015), Ophelia (2017), Leslie and Michael (2018), and Lorenzo (2019). None of these events has made landfall as a hurricane or tropical storm in mainland Portugal. However, Leslie and Ophelia have undergone extratropical transition close to mainland Portugal. We use wave buoy data at three different locations offshore mainland Portugal to characterize wind-waves during the events. The wind-waves here studied reached the coast in October. When compared with the dominant Northern Hemisphere winter wind-wave storms (December to March), the wind-waves here studied presented relatively mild wave conditions (maximum significant wave heights up to 5 m) that barely exceed wind-wave storm thresholds. Nevertheless, these wind-waves presented high mean direction variability, and induced high peak wave periods (up to 18 s).

Osobennosti gidrodinamicheskikh protsessov v rayone Bakal'skoy kosy po dannym chislennogo modelirovaniya

Hydrodynamic processes have a decisive influence on morphodynamics of the coastal area of seas. This paper studies, using computational modeling, characteristics of currents, sea level and wind waves in the Bakalskaya Spit area at storm situations of various types. For computational modeling the joined model ADCIRC+SWAN was used, which includes the barotropic hydrostatic model of currents ADCIRC and spectral wave model SWAN. The joined model uses an unstructured grid with a high spatial resolution. Calculations for a storm situation in the Black Sea (20–27 March, 2013) showed that the current field in the Bakalskaya Spit area varies greatly in terms of time and space. The greatest current velocities (up to 0.9 m/s) emerge between the island and the spit tip. Surges in the spit area reach up to 0.3 m. In the variation of sea level, oscillations with a period of ~ 10.5 h prevail. This period is close to that of the lowest mode of seiche oscillations in the Karkinitsky Bay. The wind waves are the most intensive at the western side of the spit, and during the storm peak, the height of significant waves hs reaches 2–2.5 m. The eastern side of the spit is less exposed to the waves. Here, the hs values are half as big. Between the spit tip and the island the maxima hs are 1 m. Matching calculations of waves performed using the joined model ADCIRC+SWAN and using the model SWAN showed that the joined model provides higher waves. At the western side of the spit, this increase in hs reaches 0.5 m

Contribution of Wave Setup to Projected Coastal Sea Level Changes

AbstractAlong open coasts, wind waves are a key driver of coastal changes and can be major contributors to coastal hazards. Wind wave characteristics are projected to change in response to climate change, notably due to changes in atmospheric circulation patterns and the associated surface winds. Here, a first‐order estimate of projected 20‐yr mean wave setup changes, excluding extreme events and subannual variability, is provided for sandy beaches along most of the world's coastline over the middle and end of the 21st century. Calculations are based on an ensemble of wave model projections under the representative concentration pathways (RCP) 8.5 and on empirical formulations for wave setup. Projected wave setup changes are compared to other contributors currently accounted for in regional sea level projections to extend existing projections of 21st century coastal sea level changes. Projected wave setup changes exhibit a clear spatial heterogeneity and mostly average out at global scale. However, at regional or local scale, wave setup changes are a small yet nonnegligible contributor to total coastal sea level 20‐yr mean changes (which include global mean sea level rise, GMSLR) over the middle and end of the 21st century. Wave setup can be a substantial contributor to local departures of coastal sea level changes from GMSLR. Wave setup changes should therefore be included in projections of regional patterns of coastal sea level changes. The reported long‐term changes in wave setup also advocate for the inclusion of nonstationary wave contributions to projected regional patterns of coastal sea level changes, including for studies on extreme events.

Effects of Hydrocarbons on Wind Waves in a Mine Pit Lake

The extraction and upgrading of bitumen to crude oil from the Canadian oil sands has produced large quantities of byproducts such as fluid fine tailings (FFT) and oil sands process affected water (OSPW). One reclamation strategy for these byproducts is to backfill a mined-out pit with FFT and cap it with a mix of OSPW and non-process affected water to form a pit lake. We investigated the effects of hydrocarbons, residual bitumen, on the generation and growth of wind waves, both in the laboratory and in a pit lake. In the laboratory, we compared the wind wave characteristics in the presence and absence of a hydrocarbon film. We showed that the hydrocarbon film dampens high frequency waves, resulting in a slower growing wave field dominated by lower frequency waves. These results were consistent with our field observations. Thus, it appears that the presence of a hydrocarbon film on a pit lake leads to a wind wave field dominated by longer wavelength waves that take more time to develop and grow at a slower rate. This is important since wind wave-driven mixing, in tandem with biogeochemical processes, governs water quality in mine pit lakes. Thus, this work improves understanding of the physical processes that effect water quality in mine pit lakes and enhances the ability of mine managers to conduct pit lake reclamation.

Regional wise characteristic study of significant wave height for the Indian Ocean

A proper knowledge and understanding of wind-wave characteristics and its variability on basin, regional and local scales have profound importance and practical applications in marine related activities, ocean engineering, and coastal zone management. The present study deals with the comparison of synoptic annual trends derived from space borne measurements (1992–2016), ERA-5 (1992–2018), and NCEP WWIII global run (1997–2018), monthly and seasonal wave climatology, characteristics of the annual cycle in regional basins and monthly trends of wind-wave climate on a pentad scale. Evaluation of wind-wave characteristics was performed for sub-divided domains of the IO. Further, the wave heights were segregated into percentile ranks (from 99th to 10th) by which a detailed analysis was carried out at the regional scale. Analysis of monthly and seasonal climatology signifies that the highest wave activity is observed in the extra tropical South Indian Ocean (ETSI) and the least in the Bay of Bengal. Higher percentile waves (99th, 95th, and 90th) in the ETSI are observed to be active for more than 6 months in a year. In the Arabian Sea, the maximum occurrence of 99th percentile waves (about 65%) is prominent during the month of July. An apparent pentad variation has been identified in the ETSI from 1997 to 2016 whereas, decadal variability in the north Indian Ocean (NIO) and Tropical South Indian Ocean for the lower percentile significant wave heights (25th and 10th percentiles). During the period 2007–2011, the IO experienced a considerable decreasing wave activity in all the sectors. The observed trends in annual maximum significant wave height for the ETSI and the annual mean significant wave height for the NIO are found increasing at a rate of 3.3 cm/year and 0.27 cm/year, respectively.

Characteristics of hurricane-induced wind, wave, and storm surge maxima along the U.S. Atlantic coast

Hurricanes induce multiple hazards including high wind speeds, large waves, and storm surge. The characteristics of these hazards have an important effect on the design of offshore structures and determine the suitability of simplifying assumptions for modeling, such as whether the maxima can be reasonably modeled as occurring simultaneously during the hurricane and whether the N-year values of the hazards can be modeled separately and combined. Such assumptions are common in practice. Assessing the implications of these assumptions to better inform hazard modeling along the U.S. Atlantic coast is the central objective of this paper. To this end, the characteristics of wind speeds, waves, and storm surge during hurricanes are evaluated for ten areas where development of offshore wind is proposed. The assumptions are evaluated for a model of an offshore wind turbine using time histories of hazards during intense hurricanes and using so-called environmental contours constructed through a novel implementation of the Inverse First Order Reliability Method. The results of this study show that these assumptions are reasonably accurate, especially for wind and wave in shallow waters and for wind and surge in deep waters. Hazard ratios are proposed as a suitable representation of the characteristics of hazard maxima.

The characteristics of wind waves in Lake Chaohu in 2018

基于实测数据，利用验证良好的SWAN风浪模型开展了2018年巢湖风浪变化及分布特征研究.巢湖2018年平均有效波高和波周期分别为0.16 m和1.22 s，整体春季风浪大，秋季风浪小.月均最大值出现在4月，分别为0.22 m和1.36 s，月均最小值出现在11月，分别为0.11 m和1.06 s，变化幅度分别为最大值的52%和22%.月均值整体中巢湖最大，东巢湖次之，西巢湖最小.巢湖月最大有效波高和波周期主要出现在东巢湖或中巢湖，各值月间差异显著，最大变化幅度分别为最大值的61%和27%.不同湖区计算的月均有效波高和波周期较大值分布范围所占湖区的比例不同，中巢湖与东巢湖较大，西巢湖最小.不同月份及湖区较大有效波高出现的时间占比是不一致的，9-11月份时间占比较小，将有利于蓝藻水华的出现.;In this study, the wind-wave model SWAN was used to simulate the characteristics of variations and distributions of wind waves in Lake Chaohu for the year 2018. The model was calibrated and evaluated using observational data. Results suggest that the annual mean significant wave height and wave period of Lake Chaohu during 2018 were 0.16 m and 1.26 s, respectively. The wind wave was strong in spring and weak in autumn. The monthly mean values exhibit great variations. The largest monthly values of 0.22 m and 1.36 s were obtained in April, while these values were 0.11 m and 1.06 s in November, which were the lowest during 2018 and whose variation ranges were 52% and 22% of the maximum values, respectively. Among different lake basins, monthly mean wave height in the east basin and central basin were the highest, followed by the west basin. The highest value of monthly maximum significant wave height and wave period appeared in the east basin or the central basin. The values of monthly maximum significant wave height and wave period varied significantly during different months, whose variation ranges were 61% and 27% of the maximum values, respectively. The distribution ratio of the high values of monthly significant wave height and wave period computed by model in different lake zones were large in the east basin or central basin, but it was small in the west basin. The proportion of time when the high significant wave height appeared was different during different months in different lake zones, and it was small from September to November, which would be beneficial to the emergence of cyanobacteria blooms.

Wind wave characteristics of Lake Chaohu under the influence of typhoon

Wind wave characteristics of Lake Chaohu under the influence of typhoon

Validating Ocean Wind Wave Global Hindcast with Visual Observations from VOS

Joint analysis of wind wave characteristics derived from Voluntary Observing Ships data (VOS) and the third-generation spectral wave model WAVEWATCH III v.5.16 hindcast is presented. Global distributions of significant wave heights and mean periods in both datasets demonstrate good qualitative and quantitative agreement, especially in regions with a high spatiotemporal density of observations. Simulation results and visually observed wind sea and swell show perfectly consistent patterns of directional steadiness. However, wind sea heights in WW3 are overestimated predominantly in stormy regions, while swell heights are globally underestimated. The reasons for these discrepancies in assessment of wave system components are investigated in the framework of various wave regime analyses.

Retrieval of the Statistical Characteristics of Wind Waves From the Width and Shift of the Doppler Spectrum of the Backscattered Microwave Signal at Low Incidence Angles

The Doppler spectrum (DS) of the signal backscattered at the low incidence angles from the sea surface was measured by the Ka-band radar in an experiment on a marine oceanographic platform. The directional elevation spectrum of sea waves was measured simultaneously by a six-string wave gauge mounted on a platform. At low incidence angles the backscattering mechanism is quasi-specular, and DS of the backscattered signal is calculated in the Kirchhoff approximation with the antenna pattern being taken into account. In the case of pure wind sea, the parameters of the sea waves spectrum model (wind speed and fetch) were retrieved by 2-D optimization method from measured DS shift and width. Sea wave propagation direction was obtained from the azimuthal dependence of Doppler shift. Analytical dependence of DS shift and width on incidence angle calculated from the spectrum model is in a good agreement with the experiment for incidence angles from 0° to 12°. Close values of significant wave height, the average wave period, and the variance of orbital velocities were obtained from the retrieved model spectrum and from the spectrum directly measured by the string wave gauge, which also proves the correctness of DS model.

Local katabatic winds of the Russian Federation and their observation from space using SAR imagery.

Data from the spaceborne synthetic aperture radars (SAR) provide new opportunities for observing and studying local katabatic winds (bora, foehn) in various marine regions of the Russian Federation and adjacent countries. The impact of these winds on the characteristics of small-scale wind waves leads to the formation of characteristic manifestations on the sea surface which are displayed on SAR images. Satellite SAR images, in contrast to sub-satellite observations, make it possible to see the phenomenon in the coastal zones of seas and large lakes, judge the spatial scale of the phenomenon and determine a number of it quantitative characteristics. Analysis of collected SAR images shows that local winds, bora-like and foehn-like, have similar characteristics and cover vast areas of the inland and marginal seas of the Russian Federation. The similarity of the surface manifestations of the local winds, clearly speaks about the same physical and aerohydrodynamic mechanisms of their display on SAR images. It is shown that spaceborne SAR data and images, which are two-dimensional spatial patterns of frozen wind, are extremely useful for research and monitoring local winds over the seas of the Russian Federation, especially where the network of weather stations is extremely rare.

Wind characteristic analysis based on Weibull distribution of Al-Salman site, Iraq

This paper aims to analyze the characteristic of wind speed data in Al-Salman site — Iraq using Weibull distribution. Maximum likelihood method (MLM) was used to find out two essential Weibull parameters. The best wind distribution was described by using probability density function and cumulative distribution function. Based on Weibull parameters, an analysis is carried out for various wind turbine hub heights. The characteristics of wind wave for this site are regular, uniform, and close to Rayleigh function. Furthermore, the shape factor and scale factor have fluctuated from 1.8 to 3.2 and from 5.93 m/s to 8.3 m/s for different period respectively. It was found that, at 50 m height, the mean wind speed is 5.93m/s, mean power density for this site is 219 W/m and that almost 50% of the wind speed was above 5 m/s within the total hours per annum. As consequence, this site has a potential wind power to erect small wind turbines for electricity production. Wind turbine model was proposed relying on capacity factor.

Wind-wave measurements and modelling in the shallow semi-enclosed Palk Bay

Wind-wave characteristics of the Palk Bay, a semi-enclosed water body, are studied by the wave measurements carried out at 2 locations during a one-year period. The analysis of wave data sets shows that wind-sea dominates the Palk Bay during 96% of the time and the contribution of swells are insignificant (<4%). In the Palk Bay, wind speeds are low and act on a limited fetch of only a few kilometers and thus cause waves with small amplitudes, short-wave periods, and short wavelengths. In an annual cycle, significant wave height varied from 0.2 to 1.9 m with an average of 0.6 m. The mean wave periods are mostly concentrated in a narrow range (2–4 s) with a large proportion (~48%) of the waves with a mean wave period less than 3 s. In the southern part of the Palk Bay, northerly waves are more energetic compared to the southerly waves. The wave hindcast data reproduce significant wave height with reasonable accuracy, with a positive bias of 0.08 m, root mean square error of 0.3 m and scatter index of 0.5 when the forcing winds are from Weather Research and Forecast (WRF) numerical model.

An innovative optimal RPO-FOSMC based on multi-objective grasshopper optimization algorithm for DFIG-based wind turbine to augment MPPT and FRT capabilities

Abstract Doubly Fed Induction Generator (DFIG) with consideration of its exceptional capabilities, i.e.: variable speed operation, low mechanical stresses, and excellent power quality in limited-range speed applications is a famous kind of wind turbines. Even so, there is a challenge due to its nonlinear dynamic features and several uncertainties like unknown non-linear disturbances and parameter uncertainties. Hence, this paper proposes a novel Robust Perturbation Observer based Fractional Order Sliding Mode Controller (RPO-FOSMC) for DFIG to extract the maximum power and improve the Fault Ride-Through (FRT) capability. The strong nonlinear aerodynamics of wind turbine, the uncertain dynamic parameters of induction generator and the stochastic characteristics of wind waves are constructed in perturbation term which is estimated using the proposed RPO-FOSMC. Accordingly, the perturbation compensator provides an appropriate robustness concerning different uncertain models and attains an exceptional control capability during stochastic wind waves. Considering the inherent multi-objective nature of the nonlinear control design problem, Multi-Objective Grasshopper Optimization Algorithm (MOGOA) has been implemented to augment the robustness and dynamic performance of RPO-FOSMC. Three distinct conditions are considered to compare and analyse the fast and robust dynamic performance of optimal RPO-FOSMC against other conventional approaches. Eventually, the comprehensive simulation results have revealed and validated the exceptional dynamic capability of the suggested control strategy.

Wind Waves in the Northwestern Black Sea

The study presents the results of long-term monitoring of wind waves was carried out on the offshore fixed gas production platform in the northwestern part of the Black Sea in 1995–2011. The analysis of more than 31000 wave records provided reliable statistical characteristics of wind waves in the analyzed region. It was found that the maximum wave height reached 4.8 m in summer and 8.76 m in winter. The maximum hourly wave height exceeds significant wave height by 1.9 times in the vast majority of cases. The method of annual maxima revealed that in the Karkinit Bay the maximum wave height with the return period of 50 years is equal to 9.2 m.

Study on the growth of wind wave frequency spectra generated by cold waves in the northern East China Sea

The growth of frequency spectra and spectral parameters of wind waves generated by cold waves, a kind of severe weather system, in the northern East China Sea is studied in this paper. Based on a third-generation wave action model (the Simulating WAves Nearshore model), simulations were developed to analyze the spatiotemporal characteristics of wind waves and to output spectral data. It is shown that the cold wave-induced spectra can be well described by the modified Joint North Sea Wave Project spectral form. The growth of wave spectra is comprehensively reflected by the evolution of the three characteristic parameters: peak frequency, spectral peak and wave energy. Besides, the approximations of dependences between spectral parameters and the three types of universal induced factors are obtained with the least squares method and compared systematically. Fetch and peak frequency turn out to be suitable parameters to describe the spectral parameters, while the dependences on the inverse wave age vary in different sea areas. In general, the derived relationships improve on results from previous studies for better practical application of the wind wave frequency spectrum in the northern East China Sea.

Wave transformation in the nearshore waters of Jeddah, west coast of Saudi Arabia

Many specific problems in the coastal zones require an accurate description of the wave field and knowledge of wave parameters. The studies on the spectral characteristics of wind-waves in the Red Sea are very much limited. In this study, the spectral characteristics of nearshore waves in the central Red Sea, specifically the Jeddah coast has been investigated utilizing a third generation spectral wave model, SWAN. The model results were validated against the available measured data. The seasonal and monthly characteristics and the diurnal variability of wave spectra were analysed and discussed. The wave transformation between deep, intermediate and shallow water depths were assessed at three transects – northern, central and southern regions off Jeddah. The results indicate that multi-directional swells are present in the Jeddah nearshore regions, which are propagated from the northern and southern Red Sea. The diurnal variability in the wave spectra is persistent throughout the year, although it fluctuates among the seasons according to the prevailing wind conditions. Significant attenuations in wave heights were identified in the intermediate and shallow waters, with the highest attenuation occurred in the central Jeddah coast.