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Results from a comparative study of the joint distribution of surf parameter and wave period are provided. First, two transformed joint distributions of wave height and wave period are compared. One of the distributions is a parametric model originating from a best fit to relatively broad-band field data covering a wide range of wave conditions, whilst the other distribution is theoretically based. It appears that the theoretically based distribution does not represent the features of the parametric model especially well, suggesting that parametric models should be used to describe relatively broad-banded data. Then, the theoretically based joint distribution of wave height and wave period is transformed to the joint distributions of surf parameter with wave height and wave period and it is demonstrated how these distributions are affected by the spectral bandwidth. Finally, the theoretically based distribution of wave height and wave period is also transformed to the joint distribution of wave runup time and wave period due to its relation to the stability of rubble-mound breakwaters. Comparisons are made with a limited set of data representing results from small-scale laboratory experiments related to stability of rubble-mound breakwaters. The agreement between measurements and predictions of the distribution of the surf parameter is fair, whilst the agreement is poorer for the probability of resonance.

Buis Beton ( Precast concrete pipe ) revetment is a common coastal structure to protect the shoreline from erosion. However, it is common that this type of structure face high wave run up. A continuous wave run up on the slope of the structure may reduce the life service of Buis Beton revetment. The objective of this research is to create scientific based guidance to design an efficient Buis Beton revetment against wave run up. A physical modelling test is conducted to understand the relationship between wave run up and Buis Beton revetment. The test scenario is based on the slope of the structure (θ) , structure height (L), buis beton diameter ( φ ), incoming wave height (Hi) and wave period (T). The physical modelling is conducted in 2D wave flume with laboratory scale of 1:10 with regular wave simulation. Wave run up is observed using a video camera which is later processed digitally to acquire the wave run up data. This research shows that the relative wave run up has a reciprocal functional relationship with the Iribarren Number parameter. In general, wave run up height on Buis Beton revetment is less than or equal to 2.64 the wave height, Hm0. Keywords: Revetment, buis beton, wave run-up, physical modelling

The present study examines the influence of Boreal Summer Intra-Seasonal Oscillation (BSISO) on Tropical Indian Ocean surface waves using the latest version of ECMWF reanalysis (ERA5) during summer monsoon months June through August (JJA). BSISO is a distinct mode of ISO during JJA having a northward and eastward movement from the equatorial Indian Ocean to the western Pacific Ocean. Composite analysis of anomalies of significant wave heights (SWH), wind sea, swell, and mean wave period for 8 phases of BSISO has been carried out to understand its influence. SWH anomalies in response to BSISO’s are phase-dependent. Negative SWH anomalies are noticed with strong northward and weak eastward propagation during the phases 1–3 in response to the easterly wind anomalies over the north Indian Ocean (NIO). During phases 5–7, high positive SWH anomalies (~ 0.5 m) in response to the westerly wind anomalies with northward and weak eastward propagation over NIO. Phases 4 and 8 behave like transition phases. In addition, enhanced (suppressed) SWH anomalies (~ 0.5 m) are seen during the active (break) spells of BSISO over NIO. Over the southern tip of India, negative (positive) SWH anomalies prevail during the active (break) conditions. This study clearly suggests that the wave forecast advisories during intra-seasonal time scales would be more useful for offshore and coastal activities during the summer monsoon.

One of the most important factors in design of coastal and marine structures is to determine the wave characteristics precisely. In this paper, wave characteristics of Sea of Marmara obtained during the time span between 1994 and 2014 by using the third generation spectral model MIKE 21 SW. Wind data was obtained from ECMWF ERA-Interim re-analyses wind dataset with a spatial resolution of 0.125 degree. The numerical model was calibrated with a wave data that measured for 1 year (2013) by measurement buoy on the Southern coast near the Istanbul in the Sea of Marmara. Numerical mesh optimization was also performed to obtain the most suitable domain to overcome the time efficiency problem in running time of the model. This research is recently amongst the first studies that deal with the determination of wave parameters in the Marmara Sea Basin. In addition, the relation between significant wave height and wave period is established. The results reveal that wave prediction capacity of the numerical model gives satisfactory results., Kıyı ve deniz yapılarının tasarımında en önemli faktörlerden biri dalga özelliklerinin minimum hata ile belirlenmesidir. Bu çalışmada, 1994-2014 yılları arasında Marmara Denizi'nin dalga özellikleri, üçüncü nesil spektral bir model olan MIKE 21 SW kullanılarak elde edilmiştir. Bu modelde kullanılan Rüzgâr verileri, 0.125 derecelik bir uzamsal çözünürlüğe sahip olan ECMWF ERA-Interim rüzgâr veri setidir. Sayısal model, Marmara Denizi'nde İstanbul yakınlarında bulunan Güney kıyısındaki ölçüm şamandırası ile 1 yıl (2013) için ölçülen dalga verileri ile kalibre edilmiştir. Modelin çalışma süresindeki zaman verimliliği sorununun üstesinden gelmek için sayısal ağ optimizasyonu gerçekleştirilmiştir. Bu araştırma son zamanlarda Marmara Denizi Havzası'nda dalga parametrelerinin belirlenmesi ile ilgili ilk çalışmalar arasındadır. Ayrıca, belirgin dalga yüksekliği ve dalga periyodu arasındaki ilişkiler elde edilmiştir. Sonuçlar, sayısal modelin dalga tahmin kapasitesinin tatmin edici sonuçlar verdiğini ortaya koymaktadır.

Lee, D.; Park, H.; Shin, S., and Cox, D.T., 2021. Experimental and numerical study on the wave, surge, and structure interactions on a coastal residential building. In: Lee, J.L.; Suh, K.-S.; Lee, B.; Shin, S., and Lee, J. (eds.), Crisis and Integrated Management for Coastal and Marine Safety. Journal of Coastal Research, Special Issue No. 114, pp. 156–160. Coconut Creek (Florida), ISSN 0749-0208. Residential structures in the low-lying coastal region are often suffered from devastate coastal disasters, like storms and tsunamis. To minimize the loss and improve the resilience of a coastal community, it is crucial to understand structural damage and failure mechanism under extreme from extreme coastal events. Large-scale laboratory experiments of wood-framed residential houses were conducted to investigate the wave and surge effect on the structure and the structural failure mechanism. The tests were conducted by changing a surge level, wave period, and wave height condition, and measure hydro-kinematics and structural damage process. LIDAR scanning was conducted to collect the data of damage proportion on the structure during series of wave and surge conditions. A three-dimensional RANS model, olaFlow, was used to verify our numerical model, and applied to understand hydrodynamics near the structure. Three different wave breaking conditions, including non-breaking, breaking, and broken wave are tested and consequent wave induced forces on structure are compared for both undamaged structure and damaged structure conditions. The numerical model results showed a good agreement with the experimental results in water surface and velocity. The numerical results of wave induced force in damaged conditions showed 28∼43% smaller than those in undamaged conditions. This finding highlight that the damage level of a structure could affect predicting wave load on the structure.

International audience

Breakwaters is one of type coastal structure that is mainly used as part for coastal protection purposes. Among the various types of breakwaters, likely rigid and hollow vertical pole types are one of the alternative structures for coastal protection. The utilization of this structure usually in the port area or in marina which protrudes into the sea. The pile breakwater test was carried out at laboratory experimental station for coastal engineering Buleleng Bali, on a scale of 1:10. This trial was carried out using pile materials using PVC pipes with a diameter of 6 cm. Scaling of this model is based on the piles used in the project sea dike stage A-NCICD. In testing this physical model several variations were carried out such as tata letak variation (N), wave height (h), wave period (t), distance between piles (columns) relative to diameter (B/D), and distance between piles (row) relative to diameter (b / D). Based on the test results obtained the optimal stacking configuration to reduce wave energy is a configuration with pole configuration B / D = 1; b / D = 0.5

WAM, SWAN and WAVEWATCH III® were implemented to the Finnish archipelago with a 0.1 nmi grid. A comparison with coastal wave buoy observations showed that the models agreed on the significa...

Wave measurements from a new, low-cost, real-time wave buoy (Spotter) are investigated in a comparative study as part of a site characterization study at a wave energy candidate site at King Island, Tasmania, Australia. Measurements from the Sofar Ocean Spotter buoy are compared with concurrent measurements from a Teledyne RD Instrument (RDI) 1200 kHz Work Horse ADCP and two RBRsolo3 D wave16 pressure loggers. The comparison period between 8th August – 12th October 2019 provides both the shallowest and longest continuous published comparison undertaken with the Spotter buoy.Strong agreement was evident between the Spotter buoy and RDI ADCP of key wave parameters including the significant wave height, peak wave period, and mean wave direction, with the mean values of those parameters across the full deployment period agreeing within 3%. Surface wave spectra and directional spectra are also analyzed with good agreement observed over the majority of the frequency domain, although the Spotter buoy records approximately 17% less energy within a narrow frequency band near the peak frequency when compared to the RDI ADCP. Measurements derived from the pressure loggers routinely underestimated the significant wave height and overestimated the mean wave period over the deployment period. The comparison highlights the suitability of the Spotter buoy for low-cost wave resource studies, with accurate measurements of key parameters and spectra observed.

This work investigates the sensitivity of the SWAN model with respect to state-of-the-art wave and wind datasets. The wave model was implemented and validated for the Southern Brazilian nearshore environment and simulated for 2015. Nine combinations of wave and wind datasets have been considered, aiming at establishing the boundary conditions and atmospheric forcing which best reproduce windsea and swell systems. The wave model results have been validated comparing against two buoys deployed in deep water and one buoy in shallow water. Wave parameters such as significant wave height Hs, mean wave direction Dm and peak wave period Tp have been computed and compared. Overall, the performance of the SWAN model satisfactorily reproduce the distinct waves fields for all wind and wave databases. However, the combination of datasets with ERA5 winds and CAWCR wave boundary conditions slightly outperforms the other combinations tested.

The dynamic response of the coiled tubing (CT)-in-riser system is critical to the success of offshore CT operations. The purpose of this work is to investigate the mechanical behavior of the CT and the riser and analyze the influencing factors of the coupled system. This paper builds dynamic models of the micro elements of the CT and the riser, and then a coupled model of the CT-in-riser system is presented considering the excitation of ocean loads and the coupling interaction between the inner pipe and the outer pipe. The dynamic coupled model is solved by the finite element method. A finite element model of the CT-in-riser system is built using the Abaqus/AQUA module. The effect of the operating parameters including the top injection force, the top tension, the platform offset, the annular clearance, and the friction coefficient, and the environmental parameters including the ocean depth, current speed, wave period, and wave height are discussed. The results show that the top tension should be properly controlled; the platform offset and friction coefficients should be reduced; the annular clearance should be appropriately reduced; a low current speed and wave height should be selected for operation; and the wave period and wave height have a little effect on the CT axial force. This research can provide important theoretical support for the offshore CT application.

Submerged floating tunnel (SFT) is a new type of transportation infrastructure for crossing sea straits in relatively deeper water. Compared with the fixed tunnel, the main challenge in designing a SFT is the stability maintaining in a complex hydrodynamic environment, especially for the wave-induced dynamic load. In this study, a series of systematic experiments were conducted to investigate the 2D motion characteristics (i.e., heave, sway and roll) of the SFT exposed to regular waves. The movement of the SFT model is measured by the image processing method which is a noncontact measurement. The experimental observation of SFT motion during the process of wave and SFT interaction is described in detail, and the influence of several governing parameters is thoroughly analyzed, including the wave height and period, submergence depth, buoyancy to weight ratio (BWR), and the mooring line angle. The results show that the motion amplitudes of SFT increase with the wave height increasing. The effect of wave period is related to the natural period of the structure. The sway, heave and roll of the SFT submerged beneath the water surface are much smaller than that of the SFT on the water surface. With the increase of BWR, the motion of SFT decreases. The motion amplitude increases with mooring line angle increasing. Finally, empirical equations are proposed to estimate the motion characteristics of the SFT.

Bu çalışmada, Avrupa Orta Vadeli Hava Tahmin Merkezi (ECMWF)’nin yeni yeniden değerlendirme (reanaliz) veri setinin Karadeniz bölgesi dalga tahminine katkı yapıp yapmadığı araştırılmıştır. Bu maksatla, ECMWF’in veri tabanından hem ERA5 hem de mukayese yapmak maksadıyla ERA-Interim veri setlerinin rüzgar verileri indirilmiştir. Performans değerlendirilmesi için dalga tahminlerini gerçekleştirmek maksadı ile bu rüzgar verisini kullanan üçüncü nesil dalga tahmin modeli olan SWAN varsayılan ayarlamalı olarak çalıştırılmıştır. Varsayılan ayarlamalı SWAN simülasyonu sonucunda belirgin dalga yüksekliği (Hm0), ortalama dalga periyodu (Tm02) ve ortalama dalga yönü gibi dalga parametreleri elde edilmiştir. Bu tahminler 1996 yılında NATO TU-WAVES projesi kapsamında Karadeniz’e kurulan şamandıra ölçüm istasyonlarından üçünün (Gelendzhik, Hopa, Sinop) dalga ölçümleri ile kıyaslanarak performansları irdelenmiştir. Performans değerlendirmesi sırasında hata istatistiği parametreleri, zaman serisi grafikleri, saçılım diyagramları, kuantil grafikleri ve dalga gülleri incelenmiştir. Hata istatistiği parametrelerinde örneğin Hopa şamandıra ölçüm verisi ile model veri setleri kıyaslandığında, belirgin dalga yüksekliğinde gözlenen ortalamaların farkı (bias) ERA-Interim veri setinde 0,317 m iken ERA5 veri setinde 0,261 m değerini almıştır. Tüm bu değerlendirme süreci sonucunda ise, Karadeniz özelinde ECMWF tarafından son yıllarda üretilmiş ERA5 model rüzgarlarının dalga modellerine girdi olarak tanımlandığında ERA-Interim rüzgarlarına kıyasla daha doğru dalga tahmini sağladığı sonucuna varılmıştır., This study investigated whether a new re-analysis of ECMWF contributes to wave hindcast performance in the Black Sea. For this purpose, ERA5 and ERA-Interim winds presented by ECMWF were downloaded in order to have an inter-comparison of ECMWF datasets. For performance evaluation of wave hindcasts, third generation wave hindcast model SWAN was run with a default setting. Wave hindcast outputs such as significant wave height (Hm0), mean wave period (Tm02) and mean wave direction were obtained as a result of default setting SWAN run. These hindcasts were compared with wave measurements at three buoys (Gelendzhik, Hopa, Sinop) installed in the Black Sea in 1996 as part of NATO TU-WAVES project. During performance evaluation, error statistics, time series, scatter plots, quantile graphics and wave roses were examined. In error statistics, for example bias observed for Hm0 compared to measurement and model data at Hopa was 0.317 m for ERA-Interim forcing and 0.261 m for ERA5 forcing. As a result of this all evaluation process, it was revealed that in the Black Sea ERA5 produced in the recent years by ECMWF presents a more advanced wind data set in comparison to the ERA-Interim winds because default setting SWAN model performs better in the case of ERA5 winds.

Directional wave data collected in the coastal area at 10-m water depth for a period of 1 year is used to describe the surface wave dynamics off Mumbai coast. Partitioning of the wave spectrum into locally generated waves and remotely generated swells indicates that annually 57% of the surface height variance in the study area is a result of wind-seas and the remainder is swells from the southwest. More energetic waves are dominantly young swells and are observed during Indian summer monsoon (June–September), often generated by Somali jet. The waves are also occasionally influenced by the stronger winds over the south Indian Ocean and the Southern Ocean. The wave data indicate that the north-eastern Arabian Sea has two predominant wave regimes; (i) swells with peak wave period > 10 s from the southwest and (ii) wind-seas with peak wave period

Accurate predictions of surface ocean waves in coastal areas are important for a number of marine activities. In complex coastlines with islands and fjords, the quality of wind forcing significantly affects the results. We investigate the role of wind forcing on wave conditions in a fjord system partly exposed to open sea. For this reason, we implemented the wave model SWAN at the west coast of Norway using four different wind forcing. Wind and wave estimates were compared with observations from five measurement sites. The best results in terms of significant wave height are found at the sites exposed to offshore conditions using a wind input that is biased slightly high compared with the buoy observations. Positively biased wind input, on the other hand, leads to significant overestimation of significant wave height in more sheltered locations. The model also shows a poorer performance for mean wave period in these locations. Statistical results are supported by two case studies which also illustrate the effect of high spatial resolution in wind forcing. Detailed wind forcing is necessary in order to obtain a realistic wind field in complex fjord terrain, but wind channelling and lee effects may have unpredictable effects on the wave simulations. Pure wave propagation (no wind forcing) is not able to reproduce the highest significant wave height in any of the locations.

The motions of a small-freeboard tunnel element are prone to strongly nonlinear wave-body interaction as a result of significant water-on-deck occurrence. To obtain a better prediction for the accurate and safe handling of a tunnel element in severe weather, 3D physical model tests were conducted under regular and irregular waves with long period to estimate the motions of three floating bodies (single tunnel element, pontoon and the tunnel-pontoons assembly) and predict possible resonance. The experimental results demonstrate that, due to the green water loadings, the non-zero mean heave of the tunnel and tunnel-pontoons assembly is significantly affected by roll resonant motion and has a similar dependence on the wave period as the roll in long wave regime. For wave period smaller than the roll period, the mean drift forces have substantial influence on the mean sway of all the three floating bodies, provoking greater offshore mooring tensions. Wave excitation at periods close to resonance of the heave, roll and pitch results in large local peaks in RAOs of the three floating bodies.

Making use of the fetch- and duration-limited nature of wind-wave growth inside tropical cyclones, an algorithm is developed to estimate the maximum significant wave height and dominant wave period of surface waves generated by tropical cyclone wind fields. The results of the maximum significant wave height and dominant wave period are further approximated by simple power functions of the maximum wind speed. The exponents of the power functions are almost constant, and the proportionality coefficients can be approximated by second-order polynomial functions of the radius of maximum wind speed (RMW). The predicted maximum values agree well with results derived from simultaneous wind and wave measurements obtained during 11 hurricane reconnaissance and research missions in six hurricanes.

The East China Sea, where both the strong Kuroshio Current and powerful low pressures exist, is an inevitable ocean area for various ships sailing between Japan and other Asian and European countries. The safety and economics of such shipping behaviors are often affected by the strong dynamics of the environmental matrix. The wave conditions are usually significant under high ocean winds, leading to interaction between waves and currents. In this study, the third generation wave model SWAN are used to study the wave propagation and wave-current interaction, following by its effects on the ship navigation discussed. Significant interaction between the strong Kuroshio Current and high ocean waves as well as its effects on ship safety have been found by calculations of certain wave parameters, such as significant wave height (SWH), average wave period (AWP), mean wave direction (MWD), wave length (WLEN), frequency and directional spreading.

Based on reanalysis data, we find that the Indian Ocean Dipole (IOD) plays an important role in the variability of wave climate in the equatorial Northern Indian Ocean (NIO). Significant wave height (SWH) in the equatorial NIO, especially over the waters southeast to Sri Lanka, exhibits strong interannual variations. SWH anomalies in the waters southeast to Sri Lanka correlate well with dipole mode index (DMI) during both summer and autumn. Negative SWH anomalies occur over the oceanic area southeast to Sri Lanka during positive IOD events and vary with different types of IOD. During positive prolonged (unseasonable) IOD, the SWH anomalies are the strongest in autumn (summer); while during positive normal IOD, the SWH anomalies are weak in both summer and autumn. Strong easterly wind anomalies over the southeast oceanic area of Sri Lanka during positive IOD events weaken the original equatorial westerly wind stress, which leads to the decrease in wind-sea waves. The longer wave period during positive IOD events further confirms less wind-sea waves. The SWH anomaly pattern during negative IOD events is nearly opposite to that during positive IOD events.

The relevance of long-term wave storm characterization based on in-situ measurements extends from marine ecosystems management to the design of ocean engineering structures. We analyze wave storms recorded over almost three decades (1988–2015) in three points offshore the Portuguese continental coast located between 83 and 97 m water depth. We provide Probability Distribution Functions for mean wave direction (θm), directional wave spreading ( σ θ ), significant wave height (Hs), maximum wave height (Hmax), mean wave period (Tz) and, Hmax/Hs relationship based on four storm datasets. In the highly energetic Portuguese west coast (Leixoes and Sines), Hmax and Hmax/Hs ranged between 5.5 and 17.3 m and 1.16 to 2.47, respectively. We conclude that a GEV distribution can represent Hmax and Hmax/Hs variability at the three analyzed locations. Despite the differences in the dataset lengths and the differences in the range and variability of θm, σ θ , Tz, Hs, and Hmax, we found that the range and variability of H m a x / H s are very similar for the four storm datasets. For the analyzed period, σ θ ranged between 8 and 52° and 10 to 59° in the west and south coast (Faro Atlantic and Faro Levante storms), respectively, and its variability can be described by a log-logistic distribution.

The Serangai area, Batik Nau District, North Bengkulu has the highest average abrasion speed of 20 m/year. The abrasion could cause the coastal area to erode the coastline till several tens of meters. The purpose of this study was to determine the height of the ocean waves and to determine the energy of the ocean waves that has the potential to accelerate the abrasion process in the Serangai area. The research was carried out on November 5-7, 2018 in the Serangai beach area at a depth of 5 m using SBE 26 Plus Seagauge Wave equipment. The results showed that the observed wave height was between 0.8-1.6 m with a significant wave height (Hs) of 1.38 m. In addition, the wave period ranges from 5-11 s with a significant wave period (Ts) of 8.2 s. The result also shows that the maximum wave height of 1.6 m occurred on November 7, 2018 with maximum wave energy of 1800 J/m2. This result can perhaps accelerate the abrasion process in the Serangai area. It can also be seen that the wave height in the Serangai region is higher than in several other areas in Indonesia. However, it is necessary to continue observing the wave height to see the seasonal variations in sea wave height in Serangai area.

As a result of long-term changes of the wave climate, changes in spatial and temporal scales occur in coastal regions and cause coastal morphology to change. This study investigates the effect of changes in wave climate (wave height, wave period, wave direction) on longshore sediment transport (LST) at Karasu coast, located on the southwestern coast of the Black Sea. European Center for Medium-Range Weather Forecasts (ECMWF) ERA-Interim wind data covering the period of 1979–2018 was used to obtain the wave climate of the Southwestern Black Sea coasts and to understand the dynamics of LST throughout the region. Net and gross sediment transport rates were calculated according to three different empirical and one numerical methods by using hourly significant wave heights, peak wave periods and incident wave angles. According to the 40-year wave climate data in the region, the average annual significant wave height is 0.92 m, the peak wave period is 5.53 s and the angle of wave incidence is between N-NNE sector. Waves are composed of two components; swell waves and wind waves and as a result of the study, it has been observed that swell waves have an order of magnitude larger contribution to the LST along the coast than wind waves for the respective research area, by an average factor of 12 and 17 for the net and gross LST rate, respectively. At the end of the 40-year period between 1979 and 2018, according to three different empirical and one numerical LST methods, the average net LST rate along the Karasu coast was 65,000 ± 5,000 m3/year, while the gross LST rate was 190,000 ± 20,000 m3/year. When the change of gross LST during the study period was examined, it was observed that an average decrease of 5.6% occurred. This reduction in the LST rate was observed to be associated with a 4.1% decrease in the height of the swell waves at the end of 40 years.

Drifting buoys collect wave data in the open ocean far from land and in areas with strong currents. However, the validation of the drifting buoy wave data is limited. Here, we compared the drifting buoy wave data, ERA5 wave data, and moored GPS buoy wave data. Data from 2009 to 2018 near the coast of Japan were used. The agreement of the drifting buoy-observed wave parameters with the moored GPS buoy-observed wave parameters is better than that of ERA5 wave parameters, which is statistically significant. In particular, the accuracy of the ERA5 wave heights tends to be lower where the ocean currents are fast. On the other hand, the agreement between the drifting buoy-observed wave heights and the moored GPS buoy-observed wave heights was good even in the areas with strong currents. It is confirmed that the drifting buoy wave data can be used as reference data for wave modeling study.

One of the advantages of floating offshore wind turbines (FOWTs) is that they can be designed to be easily wet towed and installed to reduce the cost of offshore construction. In this paper, a fully coupled towing system numerical model is established for a novel 10 MW FOWT concept, namely, a submerged floating offshore wind turbine (SFOWT) to investigate the towing performance. Firstly, the numerical simulation is validated by comparison with model experiment results. Then, a series of numerical simulations are conducted to predict and compare the towing performance for a three-column SFOWT (TC-SFOWT) and a four-column SFOWT (FC-SFOWT) under different wave conditions. The results show that the two forms of SFOWT have good towing performance when the significant wave height is less than 5 m, which is the maximum wave height for the allowable towing condition. The FC-SFOWT shows relatively better performance in heave motion and roll motion, but the towing force is relatively larger compared with the TC-SFOWT under the same condition. When the significant wave height is 5 m, the maximum values of heave motion, pitch motion, and roll motion of the TC-SFOWT are 2.51 m, 2.14°, and 1.38°, respectively, while they are 2.25 m, 2.70°, and 1.21°, respectively, for the FC-SFOWT. Both the roll motion and the pitch motion are satisfied with the requirement that the roll and pitch are less than 5° during the towing process. The mean towing force of FC-SFOWT is 159.1 t at the significant wave height of 5 m, which is 52.8% larger than that of TC-SFOWT. The peak period mainly influences the frequency where the response peak appears in power spectra. The findings in this paper could provide some guidelines for wet towed operations.

Variability in the characteristics of depth-induced wave breakers along a non-uniform coastal topography and its impact on the morpho-sedimentary processes is examined at the island sheltered wave-dominated micro-tidal coast, Karwar, west coast of India. Waves are simulated using the coupled wind wave model, SWAN nested in WAVEWATCH III, forced by the reanalysis winds from different sources (NCEP/NCAR, ECMWF, and NCEP/CFSR). Impact of the wave breakers is evaluated through mean longshore current and sediment transport for various wave energy conditions across different coastal morphology. Study revealed that the NCEP/CFSR wind is comparatively reasonable in simulation of nearshore waves using the SWAN model nested by 2D wave spectra generated from WAVEWATCH III. The Galvin formula for estimating mean longshore current using the crest wave period and the Kamphuis approximation for longshore sediment transport is observed realistically at the sheltered coastal environment while the coast interacts with spilling and plunging breakers.

Huiru, R.; Guosheng, L.; Linlin, C.; Yue, Z., and Ninglei, O., 2017. Simulating wave climate fluctuation in the Bohai Sea related to oscillations in the East Asian circulation over a sixty year period. Wave climate in the Bohai Sea from 1950 to 2011 was simulated with the Simulating Waves Nearshore model. Results showed that the following: (1) The significant wave height decreased; wave direction and wave period all increased in the past 62 years; the average decrease in significant wave height was 0.3 cm/y, and the increase in the wave angle was 0.12°/y. (2) The abrupt change of significant wave height occurred around 1968; the abrupt change of wave direction occurred around 1960. The characteristics of wave climate were affected by a complicated long-term process of the East Asian circulation. Four patterns for the effects of the East Asian circulation on the wave climate in the Bohai Sea were found by analysing the variation in the summer significant wave height and correlations of the signifi...

This study uses the ERA-Interim wave reanalysis data for the period 1979–2010 to assess trends in global ocean surface characteristics, including mean wave direction, significant wave heights, mean wave period, and wave energy fluxes. The Mann–Kendall’s slope estimator is used to estimate trends in the four wave parameters. The results show that, among the four wave parameters analyzed, changes in mean wave period are most extensively significant, while changes in mean wave direction are least extensively significant. The results also show that there exist seasonal and regional differences in the trends. The changes in mean wave direction are characterized by clockwise rotation of the mean wave direction along the North America west coast in December–January–February and anticlockwise rotation in the eastern tropical Pacific in March–April–May (MAM). The trend patterns for the other three parameters (wave heights, mean wave period, and wave energy flux) share substantial similarity. Their most prominent feature is significant large increases in the southern mid-latitudes (30°S–60°S) and in the western part of the North Pacific and of the North Atlantic, which are accompanied with significant decreases in the eastern part of the tropical—North Pacific. The mean wave period in Arabian Sea and the Bay of Bengal has increased in June–July–August but decreased in MAM and September–October–November.

A new, simple and inexpensive method is proposed to determine the rate of water filtration in the swash zone of lakeshore beaches. Rates of water filtration on a sandy beach were determined by measuring the residue of a tracer injected into several cylinders buried vertically in the sandy layer at various locations from the shoreline to the tip of the swash zone. This methodology enabled the separate estimation of mean infiltration and exfiltration rates. The results obtained for seashore beaches were in accordance with previous data obtained by more conventional methods. The filtration rate results for lakeshore sandy beaches were almost equivalent to seashore sandy beaches, despite a shorter swash length. This paper indicates that this is caused by a larger grain size and shorter wave period. This method presents an easy approach to determine rates of water filtration in sandy beaches and is expected to further promote studies in this field.

This study quantifies and characterises the temporal variability of shoreline recovery on a high-energy sandy coastline using a 10-year dataset of daily shoreline and sandbar positions from a Coastal Imaging station at Narrabeen-Collaroy Beach, Australia. Following a total of 82 individual storm events, rates of the cross-shore return of the shoreline to its pre-storm position were analysed. Observed rates during shoreline recovery were characterised by an overall mean of ~ 0.2 m/day. Temporal variability in rates was most evident at shorter timescales of 1–2 weeks and included rates most frequently between 0 and 0.3 m/day, less frequent more rapid rates of up to 2 m/day and also minor landward movements. This temporal variability was significantly correlated with nearshore forcing parameters describing the ratio of wave height to wave period, the cross-shore proximity (and attachment) of the sandbar to the shoreline and the rate of cross-shore sandbar migration. These findings are summarised in a new conceptual model that characterises temporal phases and rates of shoreline recovery corresponding to stages of onshore sandbar migration following a storm, from fully detached storm-deposited sandbar morphology through to complete sandbar welding with the shoreline. More gradual shoreline recovery rates are observed with fully detached and semi-attached sandbar conditions. In contrast, more rapid rates of shoreline recovery occur when sandbars are closer and attached to the shoreline, observed to be on average 3–4 times greater than for detached sandbars. In conditions with attached and semi-attached sandbars, shoreline recovery rates are negatively correlated to the forcing of nearshore wave steepness and dimensionless fall velocity, and coupled with concurrent rates of onshore sandbar migration. The findings provide insight into key parameters influencing shoreline recovery following storms.

The Seisho coastline, in Kanagawa Prefecture, Japan, has historically suffered the consequences of the many typhoons that traverse the area. In 2018, this part of the country was damaged by Typhoon Jongdari, which was a very rare typhoon that moved from the east to the west of the Japanese main island of Honshu. The goal of this study is to attempt to reproduce the beach changes that took place along the Seisho coast during the passage of this typhoon by means of a numerical simulation. First, the authors simulated the wavefield by using the SWAN model, with the maximum simulated significant wave height (5.25 m at 21:10 on 28th July) being in good agreement with observed values (5.14 m). Mean wave period and wave direction also showed close agreement with observed records. The XBeach model was then used to simulate the hydrodynamic and morphodynamic processes on Seisho coast, which indicated significant cross-shore sediment transport near the shoreline, resulting in shoreline erosion. This matched bathymetric surveys that were carried out by the government some months after the event.

In order to stabilise floating wind turbines, an innovative motion stabilisation measure is proposed and verified here through conducting a series of numerical researches with the aid of SESAM. In the research, the numerical model of a spar-supported 5 MW floating turbine was developed first to investigate its motion stability in different depths water and under different wave conditions. Then, a new concept of motion stabiliser is proposed, which consists of a number of heave plates that are connected to floating turbine foundation via structural arms. The influences of both the number of heave plates and their arm length on motion reduction are then investigated in order to explore an optimal design of the proposed stabiliser. Considering the dynamic motions of a floating turbine is mainly affected by sea waves, the motion stabilising capability of the proposed stabiliser is investigated over a wide range of wave period 4–36 s. It has been found that after using the proposed motion stabiliser, both the pitch and heave motions of the floating turbine are successfully limited within the most range of wave period, especially when the wave period exceeds 12 s.

Wave parameters estimated from two direction-finding CODAR stations located on the west and southeast coasts of Puerto Rico were compared with model (SWAN) data and nearby buoy measurements. To test the performance of the radars and their limitations within an intricate wave environment, validations in significant wave height, wave period, and peak wave direction were assessed during the week of Hurricane Matthew in 2016. Advanced, post-processed filtering methods are introduced to limit outliers in the HFR wave records. Correlations of 0.69 and 0.7 were found between spatially-averaged HFR stations and nearby buoys. The correlation between the 5 MHz HFR and the SWAN model was much higher with respect to each range cell, peaking at 0.94. The RMSE ranged between 0.36-0.68 m off the west coast where significant wave heights were also lower. Challenges presented include the presence of bimodal peaks in the spectrum and nonhomogenous conditions within the HFR coverage area

The wave period, i. e., the time interval which corresponds to a complete oscillation, is an important parameter of wave characterization. It allows the estimation of other important wave characteristics such as the length and celerity. This study aims at describing the results of a relationship among the significant, mean, and peak periods of waves generated downstream from a hydraulic jump. The frequency of vortex formation in the roller region within the hydraulic jump was used. Besides those relationships, wave lengths were also determined by the dispersion equation by considering the wave-current overlapping effect in order to identify the wave celerity. Estimated results of wave celerity were compared to their experimental results. Our findings allowed us to identify that the significant wave period was the most representative period for the characterization of a wave downstream from a hydraulic jump. RESUMO Uma característica importante para a caracterização de uma onda é o seu período, ou seja, o intervalo de tempo correspondente a uma oscilação completa. Através do período da onda é possível estimar outras importantes características da onda, tais como o comprimento e a celeridade de uma onda. Neste estudo, são apresentados resultados de uma relação entre os períodos significativo, médio e de pico, das ondas geradas a jusante de ressalto hidráulico, com a frequência de formação dos vórtices presentes na região do rolo contido dentro do ressalto hidráulico. Além destas relações, foram determinados também os comprimentos das ondas, por meio da equação de dispersão considerando o efeito de superposição de onda e corrente, para a identificação da celeridade das ondas. Os resultados estimados para a celeridade das ondas foram relacionados com os resultados experimentais obtidos para a celeridade das ondas. Através dos resultados obtidos, foi possível identificar que o período característico da onda mais representativo para a caracterização de uma onda a jusante de ressalto hidráulico foi o período significativo.

A new equation is proposed for the design of armor units on protected river banks under the combined action of ship-induced waves and river flow. Existing observed field and experimental data in the literature have been examined and a valuable database has been developed. Different conditions, including the river water depth, flow velocity, river bank slope, Froude number, wave height, wave period, and wave obliquity have been considered. Results from an empirical equation (Bhowmik, 1978) that only considers the maximum wave height and river bank slope have been compared with the results calculated by the newly developed equation. Calculated results have also been verified against field data. Results show that not only the maximum wave height and river bank slope but also the water depth, flow velocity, wave length, wave obliquity, and wave period are important parameters for predicting the mean diameter of the armor units, highlighting the multivariate behavior of protecting the river bank in the presence of ship-induced waves and river flow velocity. Keywords: River bank protection, Hydraulics, Ship-induced waves, River flow velocity, Wave period, Wave obliquity, Multivariate phenomenon

Laboratory experiments and numerical simulation were conducted to study the residual liquefaction mechanism of two-layer seabed with upper crust layer under standing waves. In this study, the buildup process of pore pressure and onset of liquefaction were firstly analyzed. Furthermore, the residual liquefaction mechanism at the nodal section was discussed. In addition, a parametric study was conducted with the present model to investigate the effects of the soil and wave characteristics to residual liquefaction. The results indicate that the liquefaction occurred before the excess pore pressure reached the maximum, then the liquefaction advanced downwards to maximal depth. Different with nodal section, the horizontal transporting of pore pressure and the accumulating of plastic volumetric strain induced by cyclic normal stress contribute to the liquefaction at the antinodal section simultaneously. The former and latter contribute about 52.6% and 47.4% respectively at the depth of 0.15 m. The thinner upper crust layer, the smaller ks1/ks2 (ks2 = 1.2 × 10−6 m/s), the shorter wave period, the higher wave steepness result in a deeper liquefaction depth. Additionally, the wave period and wave steepness had a more significant effect for the upper crust layer than the lower layer at the nodal section, but the opposite trend appeared at antinodal section.

The occurrence of freak waves off the Brazilian coast was investigated through the analysis of data recorded by three buoys deployed in the south/southeast region, at a depth of 200 m. As well documented in the literature, these events are not rare, and more than 700 waves could be classified as abnormal based on the relation between the maximum wave height (H max) and the significant wave height (H s), H max ≥ 2H s. The use of other parameters suggested in the literature, as crest amplification index (crest height/H s ≥ 1.3) or a lower limit to the significant wave (H s ≥ 2 m), drastically reduced this number, resulting in a data set more representative of rogue waves. After applying these more strict criteria, only seven “true” freak waves were found. For the first time in Brazilian waters, it was possible to identify two freak waves in the same record. It was also investigated that an index analog to crest amplification, the trough amplification index (trough depth/H s), and several waves satisfied this new condition. The analyses of the asymmetry and directional spreading of measured spectra reveal no significant correlations between these parameters and freak waves. Probably due to the relative low energy of the area when compared to other regions, the longest wave period closer to a breaking condition is 10 s.

Dillenburg, S.; Hesp, P.; Cecilio, R., and Miot da Silva, G., 2016. Wave Energy as a Control on Dune Development on two Regressive Barriers in Southern Brazil. In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 273–277. Coconut Creek (Florida), ISSN 0749-0208. Two regressive barriers (Cassino and Curumim) were developed during the middle and late Holocene along gentle re-entrants of the Rio Grande do Sul coast, and they have prograded up to 17 km and 5 km, respectively. While Cassino is marked by a surface morphology characterised predominantly by foredune ridges, Curumim displays a surface completely covered by widely spaced ridges, corresponding to phases of transgressive dunefield formation. As wave period and shoreline orientation are very similar for both barriers, and considering that they are subjected to the same deepwater wave clima...

Wang, J.; Liang, B.C.; Li, H.J.; Pan, X.Y.; Lee, D.Y., and Xu, Y., 2016. Swash motion driven by the bore and prediction of foreshore profile change. In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 492–497. Coconut Creek (Florida), ISSN 0749-0208. The prediction of a swash zone bed profile resulting from complex hydrodynamic processes is a challenging task. A series of laboratory experiments at a 2D wave flume were carried out to investigate the evolution of foreshore profiles and sediment transport in the swash zone. The swash motions and the changes of foreshore profiles at the different stages of foreshore evolution were measured for 12 cases of different combinations of wave height, wave period and water level for two different initial beach slopes (1/5 and 1/15). From the evolution of foreshore profiles detected by side looking video ...

We performed long-term wind-wave hindcast in the Yellow Sea and the Bohai Sea from the year 1988 to 2002, and then analyzed the regional wave climate. Comparisons between model results and satellite data are generally consistent on monthly mean significant wave height. Then we discuss the temporal and spatial characteristics of the climatological monthly mean significant wave heights and mean wave periods. The climatologically spatial patterns are observed as increasing from northwest to southeast and from offshore to deep-water area for both significant wave height and mean wave period, and the patterns are highly related to the wind forcing and local topography. Seasonal variations of wave parameters are also significant. Furthermore, we compute the extreme values of wind and significant wave height using statistical methods. Results reveal the spatial patterns of N-year return significant wave height in the Yellow Sea and the Bohai Sea, and we discuss the relationship between extreme values of significant wave height and wind forcing.

A unique feature observed in the tropical and subtropical coastal area is the diurnal sea-breeze/land-breeze cycle. We examined the nearshore waves at 5 and 15 m water depth during the active sea/land breeze period (January–April) in the year 2015 based on the data measured using the waverider buoys moored in the eastern Arabian sea off Vengurla, central west coast of India. Temporal variability of diurnal wave response is examined. Numerical model Delft3D is used to study the nearshore wave transformation. The wave height increased due to the sea breeze and reached its peak at ∼ 13:00 UTC at 15 m water depth, whereas the peak significant wave height is at 12:00 UTC at 5 m water depth. Due to the influence of the land/sea breeze system, the range of the peak wave period in 1 day varied up to 8 s. Reduction in the wave height of wind-sea is around 20 % and that of the swell is around 10 % from 15 to 5 m water depth.

A series of large-scale experiments are conducted to investigate the breaching process of sand dikes under wave overtopping. The dikes are constructed with uniform sand, covered with a thin clay layer on the upstream slope to prevent seepage during breaching. Wave height, wave period and dike slopes are systematically varied to examine their effects on the breaching process. Morphological development of the breach is recorded using a 3D laser scanner. The results indicate that erosion starts at the downstream edge of dike crest and the downstream dike slope gradually flattens. The breach cross-section is observed to be of a trapezoidal shape. Breach flow increases at an accelerating rate after initial overtopping until a peak flow is attained. The breach dimension and peak flow rate increase with increasing wave height, wave period, and upstream and downstream dike slopes. A dimensionless dike breach parameter is proposed to establish regression relations for the breach geometry and flow characteristics.

The spectral wave period Tm-1,0 at the toe of sea-dikes is a crucial parameter to predict wave overtopping discharge over sea-dikes. It is known from literature that this period quickly increases when waves reach shallow foreshores, however, sometimes the assumption is made that the wave period remains constant from offshore to near-shore, leading to an underestimation of the near-shore wave period. Several formulae have been proposed to resolve the underestimation of wave overtopping discharges for very shallow foreshores. These corrective formulations confirm the tendency of underestimating the overtopping discharges over a very gently sloping foreshore but are not validated for foreshore slopes gentler than 1:500. The &ldquo, equivalent slope&rdquo, method based on a recent study is inappropriate for these very gently sloping foreshores due to the breaker parameter being much smaller than seven. This study proposes an extension of the correction and finds that spectral wave periods can reach values two times those offshore.

The need of floating breakwater is increased to protect harbour by wave storm. The study and development of some model have been done in the past decade. However, their model still not effective to protect harbour against wave period greater than 5.0 second. This study deals with performance of a new type floating breakwaters in terms of heaving motion and transmission coefficient. The result compare with heaving motion of PI-type floating breakwater. Heaving motion is evaluated by using seakeeper tools, while transmission coefficient is obtained through laboratory experiment. The results indicate that the performance of proposed model better than PI-type model in terms of motion and transmission coefficient.

Dolphin, T.; Burningham, H.; Sifnioti, D.; Manning, W.; Wallbridge, S., and Farcas, A., 2020. Mixed sand/gravel beach response to the Beast from the East storms. In: Malvarez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 463–467. Coconut Creek (Florida), ISSN 0749-0208.Two large, very long-duration, shore-normal (easterly) storms worked on the Minsmere – Sizewell mixed sand and gravel (MSG) beach frontage (Suffolk, UK) in March 2018. These storms were unusual in their sustained high waves (Hs > 2.1 m, 97.5th percentile) for 140 hours from the east (16% occurrence), compared to the regional median duration of 8.5 hours per storm. Patterns in contour advance/retreat were compared with modelled nearshore wave conditions every 100 m along the 3.3 km frontage. Although there was a positive correlation between the upper supra-tidal beach and wave period, patterns in the beach response were inconsistent and zones of common behaviour could not be explained by the wave data. Postulated explanations include spatial variation in the antecedent morphology and particle-size arrangement within the MSG sediment matrix. Despite the high magnitude of work done by these storms, the lack of barrier erosion suggests that barrier stability is likely for the present sea level under these perceived more-erosive, though less common, easterly storms.

This paper presents empirical formulas for calculating the maximum wave height and period in a numerical wave hindcasting model in terms of significant wave height, mean wave period, and peakedness parameter. The formulas are developed by applying the least-square method to the wave data measured at KOGA-E1 and KOGA-S2, which are located in the Japan/East Sea and on the southeast coast of the Korean Peninsula, respectively. The developed formulas are validated by comparing with the wave measurements around the Korean Peninsula. The formulas are shown to concur well with the measurements even in the Yellow Sea where the tide is very strong. To examine the applicability of the formulas in a wave hindcasting model, numerical simulation has been performed for wind wave generation around the Korean Peninsula. The maximum wave height and period have been calculated using the wave parameters computed in the numerical simulation. The calculated maximum wave height and period are then compared with the measurements to show that the developed formulas can be used for long-term prediction of the maximum wave height and period in a numerical wave hindcasting model. This comparison shows that the predicted maximum wave height and period agree well with the measured ones.

Altimeter data provides a precise measurement of wave parameters especially over open ocean. Now, several attempts were made to retrieve wind and wave information towards coastal regions. SARAL/Altika is a first of its kind to operate at such a high frequency to provide better observation of coastal regions. The present study is especially important for the Indian coasts because most of the in-situ observations are either coastally located or at deep water.