Extreme Values of Wind Speed and Wave Height in the North Sea for Defining Design Criteria of Offshore Installations

1983 ◽  
pp. 143-148
Author(s):  
E. Bouws ◽  
J. J. E. Pöttgens
Keyword(s):  
Wind Speed ◽  
Wave Height ◽  
North Sea ◽  
Extreme Values ◽  
Design Criteria ◽  
The North ◽  
Offshore Installations ◽  
The North Sea

Relative Motion During Single Blade Installation: Measurements From the North Sea

2020 ◽  
Author(s):  
Aljoscha Sander ◽  
Andreas F. Haselsteiner ◽  
Kader Barat ◽  
Michael Janssen ◽  
Stephan Oelker ◽  
...  
Keyword(s):  
Wind Speed ◽  
Wave Height ◽  
North Sea ◽  
Relative Motion ◽  
Significant Wave Height ◽  
Offshore Wind ◽  
Wave Excitation ◽  
Significant Wave ◽  
The North ◽  
The North Sea

Abstract During single blade installation in offshore wind farms, relative motion between nacelle and blade root due to wind and wave excitation pose a significant challenge. Wave excitation can be modelled considerably well by employing state-of-the-art simulation tools and can, therefore, be included in installation planning. Other phenomena, such as flow-induced vibrations are hard to capture and hence challenging to account for when defining installation procedures and limitations. Here, we present measurements conducted during the installation of an offshore wind farm consisting of multi-megawatt turbines installed on monopile foundations in the North Sea. A custom-built sensor capturing linear & angular acceleration and GPS-data was deployed atop the nacelle. Both partially and fully assembled turbines displayed complex oscillation orbits, swiftly changing amplitude and direction. Mean nacelle deflection correlated strongly with significant wave height as well as mean wind speed. As wind speed and significant wave height showed a strong correlation as well, it is difficult to discern which load drives the observed relative motions. While wind loads are significantly smaller than wave loads on partially assembled turbines under installation conditions, additional momentum induced by vortex shedding may prove sufficient to cause the observed effects.

scholarly journals MISALIGNMENT AND LAG TIME OF WIND AND WAVE OCCURRENCE BASED ON 10 YEARS MEASUREMENTS IN THE NORTH SEA NEAR THE GERMAN COAST

2018 ◽  
pp. 13
Author(s):  
Arndt Hildebrandt ◽  
Remo Cossu
Keyword(s):  
Wind Speed ◽  
Wave Height ◽  
North Sea ◽  
Offshore Wind ◽  
Wave Loads ◽  
Wind Speeds ◽  
The North ◽  
The North Sea ◽  
The Impact ◽  
The Waves

There are several intentions to analyze the correlation of wind and wave data, especially in the North Sea. Fatigue damage is intensified by wind and wave loads acting from different directions, due to the misaligned aerodynamic damping of the rotor regarding the wave loads from lateral directions. Furthermore, construction time and costs are mainly driven by the operational times of the working vessels, which strongly depend on the wind and wave occurrence and correlation. Turbulent wind can rapidly change its direction and intensity, while the inert water waves react slowly in relation to the wind profile. Tuerk (2008) investigates the impact of wind and turbulence on offshore wind turbines by analyzing data of four years. The study shows that the wave height is increasing with higher wind speeds but when the wind speed drops the reaction of the waves is postponed. The dependence of the wave height on the wind speed is varying because of the atmospheric stability and different wind directions. Fischer et al. (2011) estimated absolute values of misalignment between wind and waves located in the Dutch North Sea. The study presents decreasing misalignment for increasing wind speeds, ranging up to 90 degrees for wind speeds below 12 m/s and up to 30 degrees for wind speeds above 20 m/s. Bredmose et al. (2013) present a method of offshore wind and wave simulation by using metocean data. The study describes characteristics of the wind and wave climate for the North and Baltic Sea as well as the directional distribution of wind and waves. Güner et al. (2013) cover the development of a statistical wave model for the Karaburun coastal zone located at the southwest coast of the Black Sea with the help of wind and wave measurements and showed that the height of the waves is directly correlating with the duration of the wind for the last four hours.

Further Investigation upon the Water Movements in the English Channel. Drift-Bottle Experiments in the Summers of 1927, 1928 and 1929, with Critical Notes on Drift-Bottle Experiments in General.

1930 ◽  
Vol 17 (1) ◽  
pp. 241-275 ◽  
Author(s):  
J. N. Carruthers
Keyword(s):  
Wind Speed ◽  
North Sea ◽  
English Channel ◽  
The North ◽  
Different Types ◽  
The North Sea ◽  
The Common ◽  
Relationship Of ◽  
Great Simplicity ◽  
Simple Surface

In July–August of three different years common surface-floating bottles were set adrift at International Station E2 (49° 27' N.—4° 42' W.). With them, various types of drag-fitted bottles were also put out. The journeys accomplished are discussed, and the striking differences as between year and year in the case of the common surface floaters, and as between the different types in the same year, are commented upon in the light of the prevailing winds. An inter-relationship of great simplicity is deduced between wind speed and the rate of travel of simple surface floating bottles up-Channel and across the North Sea from the results of experiments carried out in four different summers.

What can idealized storm surge simulations tell us about worst case scenarios?

2021 ◽  
Author(s):  
Elin Andrée ◽  
Jian Su ◽  
Martin Drews ◽  
Morten Andreas Dahl Larsen ◽  
Asger Bendix Hansen ◽  
...  
Keyword(s):  
Wind Speed ◽  
Sea Level ◽  
North Sea ◽  
Wind Direction ◽  
Water Levels ◽  
Sea Levels ◽  
The North ◽  
The North Sea ◽  
Sea Coast ◽  
North Sea Coast

<p>The potential impacts of extreme sea level events are becoming more apparent to the public and policy makers alike. As the magnitude of these events are expected to increase due to climate change, and increased coastal urbanization results in ever increasing stakes in the coastal zones, the need for risk assessments is growing too.</p><p>The physical conditions that generate extreme sea levels are highly dependent on site specific conditions, such as bathymetry, tidal regime, wind fetch and the shape of the coastline. For a low-lying country like Denmark, which consists of a peninsula and islands that partition off the semi-enclosed Baltic Sea from the North Sea, a better understanding of how the local sea level responds to wind forcing is urgently called for.</p><p>We here present a map for Denmark that shows the most efficient wind directions for generating extreme sea levels, for a total of 70 locations distributed all over the country’s coastlines. The maps are produced by conducting simulations with a high resolution, 3D-ocean model, which is used for operational storm surge modelling at the Danish Meteorological Institute. We force the model with idealized wind fields that maintain a fixed wind speed and wind direction over the entire model domain. Simulations are conducted for one wind speed and one wind direction at a time, generating ensembles of a set of wind directions for a fixed wind speed, as well as a set of wind speeds for a fixed wind direction, respectively.</p><p>For each wind direction, we find that the maximum water level at a given location increases linearly with the wind speed, and the slope values show clear spatial patterns, for example distinguishing the Danish southern North Sea coast from the central or northern North Sea Coast. The slope values are highest along the southwestern North Sea coast, where the passage of North Atlantic low pressure systems over the shallow North Sea, as well as the large tidal range, result in a much larger range of variability than in the more sheltered Inner Danish Waters. However, in our simulations the large fetch of the Baltic Sea, in combination with the funneling effect of the Danish Straits, result in almost as high water levels as along the North Sea coast.</p><p>Although the wind forcing is completely synthetic with no spatial and temporal structure of a real storm, this idealized approach allows us to systematically investigate the sea level response at the boundaries of what is physically plausible. We evaluate the results from these simulations by comparison to peak water levels from a 58 year long, high resolution ocean hindcast, with promising agreement.</p>

Searching for Factors that Limit Observed Extreme Maximum Wave Height Distributions in the North Sea

2008 ◽  
pp. 127-138 ◽  
Author(s):  
Gerrit Burgers ◽  
Frits Koek ◽  
Hans de Vries ◽  
Martin Stam
Keyword(s):  
Wave Height ◽  
North Sea ◽  
Maximum Wave Height ◽  
The North ◽  
The North Sea

scholarly journals A prospective observational study of why people are medically evacuated from offshore installations in the North Sea

BMJ Open ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. e037558
Author(s):  
Anne Waje-Andreassen ◽  
Øyvind Østerås ◽  
Guttorm Brattebø
Keyword(s):  
Observational Study ◽  
North Sea ◽  
Prospective Observational Study ◽  
Oil And Gas ◽  
Record System ◽  
The North ◽  
Transport Services ◽  
Offshore Installations ◽  
Severity Scores ◽  
The North Sea

ObjectivesFew studies have described evacuations due to medical emergencies from the offshore installations in the North Sea, though efficient medical service is essential for the industrial activities in this area. The major oil- and gas-producing companies’ search and rescue (SAR) service is responsible for medical evacuations. Using a prospective approach, we describe the characteristics of patients evacuated by SAR.Design and settingA prospective observational study of the offshore primary care provided by SAR in the North Sea.MethodsPatients were identified by linking flight information from air transport services in 2015/2016 and the company’s medical record system. Standardised forms filled out by SAR nurses during the evacuation were also analysed. In-hospital information was obtained retrospectively from Haukeland University Hospital’s information system.ResultsA total of 381 persons (88% men) were evacuated during the study period. Twenty-seven per cent of missions were due to chest pain and 18% due to trauma. The mean age was 46.0 years. Severity scores were higher for cases due to medical conditions compared with trauma, but the scores were relatively low compared with onshore emergency missions. The busiest months were May, July and December. Weekends were the busiest days.ConclusionThree times as many evacuations from offshore installations are performed due to acute illness than trauma, and cardiac problems are the most common. Although most patients are not severely physiologically deranged, the study documents a need for competent SAR services 24 hours a day year-round. Training and certification should be tailored for the SAR service, as the offshore health service structure and geography differs from the structure onshore.

Prediction of Relative Motion and Probability of Contact Between FPSO and Shuttle Tanker in Tandem Offloading Operation

2002 ◽  
Author(s):  
Haibo Chen ◽  
Torgeir Moan ◽  
Sverre Haver ◽  
Kjell Larsen
Keyword(s):  
North Sea ◽  
Extreme Values ◽  
Simulation Models ◽  
Point Of View ◽  
Simulation Code ◽  
The North ◽  
Simulation Based ◽  
The North Sea ◽  
Sensitivity Studies ◽  
Tandem Offloading

Tandem offloading safety between FPSO and shuttle tanker is under concern. A few collisions between the two vessels have happened in the North Sea in recent years. In these incidents, excessive relative motions (termed as surging and yawing in this paper) between FPSO and tanker are identified as “failure prone situations” which have contributed to the initiation of most collision incidents. To quantitatively assess the probability of surging and yawing events, and more importantly, to effectively reduce their occurrence in tandem offloading operation, we present a simulation-based approach in this paper, which is carried out by a state-of-the-art time-domain simulation code SIMO. The SIMO simulation models are setup and calibrated for a typical North Sea purpose-built FPSO and a DP shuttle tanker. This 2-vessel system motion in tandem offloading is simulated. The simulated relative distance and relative heading between FPSO and tanker are analyzed by fitting their extreme values into statistical models. This gives out probabilities of surging and yawing events. Sensitivity studies are performed to analyze contributions from various technical and operational factors. Measures to minimize the occurrence of surging and yawing from design and operational point of view are proposed.

Gas Turbine Intake Filter Systems Related to Offshore Platform Installations

1985 ◽  
Author(s):  
M. H. P. Kimm ◽  
D. Langlands
Keyword(s):  
Gas Turbine ◽  
North Sea ◽  
Specific Reference ◽  
Ideal Condition ◽  
Air Filtration ◽  
Contributing Factors ◽  
The North ◽  
Offshore Installations ◽  
Production Platform ◽  
The North Sea

This Paper covers various aspects with respect to the selection and operation of air filtration associated to offshore gas turbine installations. As the Offshore North Sea industry moves into its second decade, Operators are still trying to improve machine availability and reduce maintenance costs. One of the main contributing factors in their failure to achieve the ideal condition has been poor inlet air filtration caused by bad design and incorrect filter selection. The majority of offshore installations are equipped with filter systems which were originally designed for use on ocean-going vessels. The performance of what has become known as the “High Velocity Salt Eliminator System” has, in most cases, been unsatisfactory, thereby creating a necessity for a continuing search into alternative filter systems. The experiences of most Operators in the North Sea have been very similar, and examination of the platform environment explains why this should be the case. To emphasize the affects of poor air filtration and the savings that can be achieved by the Operator in recognising and correcting the problems, specific reference is made to the experience of Mobil North Sea with the Beryl Alpha Production Platform.

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