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1

Analysis of the influence of wave loads on offshore installations

Mustafayev Vahid T., Nasirov Chingiz R.

Nafta-Gaz

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2024

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R. 80, nr 2

91--95

PL

Given that the loads affecting offshore installations exhibit a broad range of variability in both temporal and spatial parameters, these loads are among the least studied components in the consideration of offshore installations as integrated systems. The existing calculation models and approaches used in design are rather conditional. When determining loads affecting offshore installations, the most common error is the description of loads in terms of time parameters, which lead to a distortion of the dynamic behavior of offshore installations. This is primarily because dynamic effects on the structure clearly demonstrate feedback between the influence of loads and the system itself. These loads can be classified as external and internal. Internal loads include loads from installation and construction processes, as well as loads from auxiliary and technological equipment, and external loads include ice, seismic, snow and wind loads. There are several approaches to solving problems related to the impact of wind waves on offshore installations. For this reason, an analysis and comparison of these methods were conducted to improve modeling process of offshore installations. Taking into account the impact of wave loads is a critical aspect of in developing the calculation model for the operational assessment of the residual resource of offshore installations.

EN

Biorąc pod uwagę, że obciążenia wpływające na instalacje morskie wykazują szeroki zakres zmienności, zarówno pod względem parametrów czasowych, jak i przestrzennych, obciążenia te są jednymi z najmniej zbadanych aspektów w rozważaniach nad instalacjami morskimi jako zintegrowanymi systemami. Istniejące modele obliczeniowe i koncepcje stosowane w projektowaniu są raczej uzależnione od warunków. Podczas określania obciążeń wpływających na instalacje morskie, najczęstszym błędem jest opis obciążeń w kategoriach parametrów czasowych, co prowadzi do zniekształcenia dynamicznego zachowania instalacji morskich. Dzieje się tak przede wszystkim dlatego, że dynamiczne oddziaływanie na konstrukcję wyraźnie wykazuje sprzężenie zwrotne między wpływem obciążeń a samym systemem. Obciążenia te można sklasyfikować jako zewnętrzne i wewnętrzne. Obciążenia wewnętrzne obejmują obciążenia związane z procesami instalacji i budowy, a także obciążenia związane z wyposażeniem pomocniczym i technologicznym, natomiast obciążenia zewnętrzne obejmują obciążenia spowodowane lodem, wstrząsami sejsmicznymi, śniegiem i wiatrem. Istnieje kilka koncepcji rozwiązywania problemów związanych z oddziaływaniem fal wiatrowych na instalacje morskie. Z tego powodu przeprowadzono analizę i porównanie tych metod w celu usprawnienia procesu modelowania instalacji morskich. Uwzględnienie wpływu obciążeń falowych jest krytycznym aspektem przy opracowywaniu modelu obliczeniowego do oceny operacyjnej pozostałych zasobów instalacji morskich.

2

Sea spray volume flux estimation using joint statistics of wind and waves

Myrhaug Dag, Leira Bernt J., Radhakrishnan Gowtham, Holm Håvard

Oceanologia

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2022

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No. 64 (4)

789--793

EN

This article provides estimates of the sea spray volume flux using joint statistics of wind and waves. This is achieved by combining the sea spray volume flux parameterization proposed by Xu et al. (2021) with the joint statistics of wind and waves provided by Bitner-Gregersen (2015). Both the sea spray volume flux formula and the joint statistics of wind and waves represent conditions for wind waves from the North-West Shelf of Western Australia. The expected value and the variance of the sea spray volume flux for a range of realistic wind and wave conditions are presented, as well as an illustrative example. Comparison is also made with data from Xu et al. (2021) showing a reasonable agreement for the relevant subset of the data.

3

Influence of the climatic variations in the wind waves parameters on the alongshore sediment transport

Divinsky Boris V., Kosyan Ruben D.

Oceanologia

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2020

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No. 62 (2)

190--199

EN

The purpose of this work was to analyze the influence of climatic variability of wind waves and swell parameters in the coastal zone on the sediment transport and to assess the contribution of the swell to the formation of alongshore fluxes. The object of research is the Anapa bay-bar (the Black Sea). Mathematical modeling has shown that in the Anapa bay-bar area the average annual wind waves and swell powers have significant interannual variability. For the period from 1979 to 2017, in the southern part of the bay-bar, there was a statistically significant decrease in the share of swell in the alongshore transport, directed from NW to SE, in the central part – an increase in the contribution of swell to the total sediment flow from SE to NW, in the northern part – probable increase in flows to NW and decrease – to SE. Such a dynamic is consistent, in general, with experimental observations of the processes of erosion and accumulation of beach-forming material along the Anapa bay-bar coastline. A separate description of the bottom sediment fluxes under the influence of wind waves and swell made it possible to explain the fluctuations of the coastline over a climatic period.

4

Extreme wind waves in the Black Sea

Divinsky Boris V., Fomin Vladimir V., Kosyan Ruben D., Ratner Yuri D.

Oceanologia

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2020

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No. 62 (1)

23--30

EN

Results of the analysis of a long-term data set, including fields of significant wave heights of the surface wave components, and mixed (total) wave field in the Black Sea are presented. The data set was collected on the basis of retrospective calculations using the MIKE 21 SW spectral wave model with the atmospheric forcing based on the ERA-Interim data in the period from 1979 to 2017. A criterion is used to isolate the swell waves from the initial wave data set that takes into account the wave age. We used the experimental data to develop a regression relationship showing that the maximum possible wave height can exceed the significant wave height approximately one and a half times. Analysis of the spatial distribution of wave heights in the Black Sea suggests that a possibility exists that significant wave height of storm waves can be as high as ∼12 m. This result indicates that the actual heights of maximum waves in the Black Sea can reach 18-19 m. Three regions are distinguished on the basis of the wave potential. The times of manifestation of extreme situations in these regions are different: in the southwestern part of the sea, extreme storm situations occur, as a rule, in December-January; in the region south of the Crimea Peninsula this happens in February; in the northeastern part of the sea they occur in November. It was also found that the south-southeastern and eastern parts of the sea are most affected by swell.

5

Case-Study Modelling Analysis of Hydrodynamics in the Nearshore of the Baltic Sea Forced by Extreme Along-shore Wind in the Case of a Cross-shore Obstacle

Sokolov A., Chubarenko B.

Archives of Hydro-Engineering and Environmental Mechanics

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2018

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Vol. 65, nr 3

163--176

EN

In the current study we use a three-dimensional model with hydrodynamic and spectral wave modules operating in a coupled mode to simulate the response of currents and wind wave fields to winds of 20–25 m/sec offshore of the protective structure of the Saint Petersburg Flood Prevention Facility Complex. The model was calibrated against field data, which allowed us to obtain a tool describing storm situations in the eastern part of the Gulf of Finland with a satisfactory accuracy. The numerical modeling showed that the protective dam did not have a noticeable effect on the levels of stormsurge, significantwave height, or current speed in areas seaward of the dam. The increase in erosion processes on the southern shore of the easternmost part of the Gulf of Finland in recent past has most probably been related to other factors. We found that if a west or south-west wind of at least 25 m/s blows over the Baltic Sea for at least 16 hours, the level of storm surges seaward of the dam may reach 3 or more meters. An artificial strengthening of the coastline and the creation of shore protection structures are recommended.

6

Zróżnicowanie natężenia przepływu w wodach układu hydrograficznego zachodniej części Martwej Wisły i Wisły Śmiałej

Cieśliński R., Pietruszyński Ł., Duda F.

Przegląd Geofizyczny

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2017

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Z. 3-4

197--215

PL

Celem głównym pracy jest próba określenia wielkości natężenia przepływu na całym zachodnim odcinku Martwej Wisły i Wisły Śmiałej, włącznie z basenami portowymi oraz określenie głównych uwarunkowań wpływających na zróżnicowanie wielkości przepływu. Główne prace polegały na badaniach terenowych, podczas których wykonano pomiary natężenia przepływu przy wykorzystaniu metody ADCP. Wykonano również szczegółową kwerendę materiałów źródłowych. Na podstawie uzyskanych wyników można stwierdzić, że warunki hydrologiczne obu rzek są ściśle powiązane z oddziaływaniem morza. To morze decyduje o obiegu wody wewnątrz akwenów, procesach i zjawiskach tam występujących itd. Dynamika oddziaływania morza wynika z kolei z uwarunkowań hydrometeorologicznych, takich jak wiatr czy zmiany poziomu wody. W konsekwencji mamy do czynienia z dwoma akwenami silnie ze sobą powiązanymi hydrologicznie. Prądy tam występujące mają charakter prądów „chaotycznych”, związanych z kierunkiem i prędkością wiatru wiejącego w danej chwili. W obu akwenach zdarzają się prądy dwukierunkowe tj. w kierunku morza i w głąb lądu. Pomierzone przepływy na Martwej Wiśle mieściły się w zakresie od 9,41 do 22,03 m3•s-1, a na Wiśle Śmiałej 34,41 m3•s-1. Z materiałów źródłowych wynika, że na Martwej Wiśle przepływy mogą osiągnąć nawet 178 m3•s-1, a na Wiśle Śmiałej 40 m3•s-1.

EN

The main aim of this study was to determine the size of the flow around the western stretch of the Martwa Wisła and Wisła Śmiała, including swimming pools port and identify the key determinants affecting differences in flow rate. The main work consisted of field work, during which the measurements of the flow rate using the ADCP method. Also made a detailed query source materials. Based on the obtained results it can be stated that the hydrological conditions of both rivers are closely linked with the influence of the sea. It determines the sea water circulation inside waters, processes and phenomena occurring there etc. The dynamics of the impact of the sea in turn caused by hydro-meteorological conditions such as wind or water level changes. Consequently, we have to deal with the two bodies hydrologically closely linked. Streams occurring there are “chaotic” current related to the direction and speed of winds at the time. There are both basins bi-directional currents, ie. in the direction of the sea and inland. The resulting flows of the Martwa Wisła ranged from 9.41 to 22.03 m3•s-1, while on the Wisła Śmiała dared 34.41 m3•s-1. On the basis of source materials, these values can reach up to 178 m3•s-1 on the Martwa Wisła and 40 m3•s-1 on the Wisła Śmiała.

7

Relation between the type of wave exposure and seagrass losses (Cymodocea nodosa) in the south of Gran Canaria (Canary Islands - Spain)

Portillo E.

Oceanological and Hydrobiological Studies

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2014

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Vol. 43, No. 1

29--40

EN

Effects of different types of wave events on Cymodocea nodosa seagrass meadows were observed and investigated by quantitative and qualitative evaluation of material washed ashore a few days after the events. The studied seagrass meadows are located on the south coast of the island of Gran Canaria (Canary Islands - Spain) and they are protected from frequent swells arriving from the North Atlantic. However, sporadic phenomena associated with winter storms occasionally hit this coastline, causing the loss of entire plants (fresh leaves with rhizomes and roots attached). An unusual type of southern swells generated in the South Atlantic also reaches the Islands in spring and summer. A clear relation was observed between the wave events (southern swells and storm waves) and the material cast ashore over the following days, with differences in composition (fresh vs. decaying leaves) depending on the type of event. After southern swells, detached portions of C. nodosa consisted mostly of decaying leaves shed after senescence. These old swells cause frictional drag with moderate oscillations over a wider range at greater depths, removing only decaying leaves from the seagrass meadows and favoring the natural clean-up process.

8

Spatial patterns of the wave climate in the Baltic Proper and the Gulf of Finland

Soomere T., Räämet A.

Oceanologia

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2011

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No. 53 (1-TI)

335-371

EN

We make an attempt to consolidate results from a number of recent studies into spatial patterns of temporal variations in Baltic Sea wave properties. The analysis is based on historically measured and visually observed wave data, which are compared with the results of numerical hindcasts using both simple fetch-based one-point models and contemporary spectral wave models forced with different wind data sets. The focus is on the eastern regions of the Baltic Sea and the Gulf of Finland for which long-term wave data sets are available. We demonstrate that a large part of the mismatches between long-term changes to wave properties at selected sites can be explained by the rich spatial patterns in changes to the Baltic Sea wave fields that are not resolved by the existing wave observation network. The spatial scales of such patterns in the open sea vary from > 500 km for short-term interannual variations down to about 100 km for long-term changes.

9

Trends and extremes of wave fields in the north-eastern part of the Baltic Proper

Broman B., Hammarklint T., Rannat K., Soomere T., Valdmann A.

Oceanologia

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2006

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No. 48 (S)

165-184

EN

The paper analyses one of the longest contemporary wave measurements in the northern Baltic Sea, performed at Almagrundet 1978-2003. This record contains the roughest instrumentally measured wave conditions (significant wave height = c. 7.8 m) in the northern Baltic Proper until December 2004. The data for the years 1979-95, the period for which the data are the most reliable, show a linear rising trend of 1.8% per annum in the average wave height. The seasonal variation in wave activity follows the variation in wind speed. The monthly mean significant wave height varies from 0.5 m in May-July to 1.3-1.4 m in December-January. No corrections have been made in the analysis to compensate for missing values, for their uneven distribution, or for ice cover.

10

Application of numerical wave model swan for analysis of waves in the surf zone

Reda A., Paplińska B.

Oceanological Studies

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2002

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Vol. 31, No. 1-2

5-21

EN

The numerical wave model SWAN has been used for wave modelling at the Coastal Research Facility at Lubiatowo. This study tested the performance of SWAN in the surf zone with four longshore bars. This is the first stage of the work heading towards a widening of the wave forecast for the Polish nearshore. The analysis concerned changes in the space and time of chosen wave parameters: significant wave height, mean wave period, mean wave direction. Modelled wave parameters were compared with measurements taken during the field experiment in 1996. The conformity is generally reasonable although the model tends to underestimate the significant wave height, particularly for higher waves. Further studies are planned to determine the reason behind this phenomenon.

11

Maximum-entropy probability distribution of wind wave free-surface elevation

Cieślikiewicz W.

Oceanologia

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1998

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No. 40 (3)

205-229

EN

The probability density function of the surface elevation of a non-Gaussian random wave field is obtained. The derivation is based on the maximum entropy (information) principle with the first four statistical moments of the surface elevation used as constraints. The density function is found by the use of the Lagrangian multipliers method and it is shown that only two of four Lagrangian multipliers are independent. The applied method of numerical solution is described in detail and the useful nomograms that give the Lagrangian multipliers as functions of skewness and kurtosis are calculated and incorporated in the paper. For slightly nonlinear waves the approximate maximum-entropy probability distribution is developed. The condition of the existence of this approximate distribution agrees with the empirical criterion for small deviations from the Gaussian distribution of random water waves. The theoretical results compare well with field experiment data of Ochi and Wang (1984), even in the strongly non-Gaussian case.