scholarly journals STATISTICAL DISTRIBUTION OF WAVE HEIGHTS IN CORRELATION WITH ENERQ7 SPECTRUM AND WATER DEPTH

1964 ◽  
Vol 1 (9) ◽  
pp. 8
Author(s):  
L.A. Koele ◽  
P.A. De Bruyn
Keyword(s):  
Water Depth ◽  
Wave Motion ◽  
Statistical Distribution ◽  
Coastal Structures ◽  
Coastal Morphology ◽  
Delta Area ◽  
The North ◽  
Wave Measurements ◽  
Wave Heights ◽  
The North Sea

Wave motion has been studied at various places in the south western part of the Netherlands (the Delta area) as part of a study on coastal morphology and the design of coastal structures. The main part of this study deals with the statistical distribution of wave heights in relation to: a. the height of the sea surface at fixed points, as a function of time; b. the water depth; c. the energy spectrum of the wave motion. The results of theoretical studies by D.E.Cartwright and M.S.Longuet Higgins (lit. 1) and data on wave measurements obtained by Rijkswaterstaat in the North Sea were used. These measurements were taken by means of an electrical step-capacity gauge, with wireless transmission of the data to shore . Three gauges, fastened to fixed poles (named E, X and T) were placed at points at depths of 5, 10 and 15 meters respectively, (fig. 1).

scholarly journals WAVE CLIMATE ANALYSIS FOR ENGINEERING PURPOSE

1976 ◽  
Vol 1 (15) ◽  
pp. 2 ◽  
Author(s):  
Hans H. Dette ◽  
Alfred Fuhrboter
Keyword(s):  
Wave Climate ◽  
Incoming Wave ◽  
Offshore Area ◽  
The North ◽  
Wave Measurements ◽  
Wind Velocities ◽  
Wave Heights ◽  
The North Sea ◽  
One Year ◽  
Climate Analysis

The North Sea (Fig. 1) is known as a random sea with depths in the southern part between 40 m and 100 m so that in contrary to the Atlantic and Pacific coastlines deep sea wave conditions do not exist. After four years of comprehensive wave measurements in the offshore area of the Island of Sylt near the Danish border a general analysis of the wave climate in that region was possible. In this paper results and suggestions will be presented under the aspect of replacing qualitative judgements by quantitative statements which are derived from the knowledge of the adjacent wave climate. Because the wave action varies from year to year a general time unit is not advisable for the evaluation of shore processes; therefore the time scale should be substituted by the integral of incoming wave energy occurring after a certain time. The investigated method of expressing the total energy of one season or one year in the electrical unit Kilowatthour (kWh) per meter (m) width of shoreline could prove in future as a feasible way of classifying the irregular seasonal and yearly wave intensities. It is further shown that wave measurements over a period of several years can be sufficient for the investigation of correlations between the wind velocities occurring from all directions and the resulting wave heights. In case of satisfying correlation factors it will then be possible to carry out feedback operations for periods from which only records of wind velocities and directions are available and even to hindcast the wave heights for certain not yet measured wind velocities.

scholarly journals North Atlantic storm driving of extreme wave heights in the North Sea

2017 ◽  
Vol 122 (4) ◽  
pp. 3253-3268 ◽  
Author(s):  
R. J. Bell ◽  
S. L. Gray ◽  
O. P. Jones
Keyword(s):  
North Sea ◽  
North Atlantic ◽  
Extreme Wave ◽  
The North ◽  
Wave Heights ◽  
The North Sea

Successful transient EM survey in the North Sea at 100 m water depth

2008 ◽  
Author(s):  
Anton Ziolkowski ◽  
David Wright ◽  
Guy Hall ◽  
Craig Clarke
Keyword(s):  
North Sea ◽  
Water Depth ◽  
The North ◽  
The North Sea

Albinistic common seals (Phoca vitulina) and melanistic grey seals (Halichoerus grypus) rehabilitated in the Netherlands

2010 ◽  
Vol 60 (3) ◽  
pp. 273-281 ◽  
Author(s):  
Nynke Osinga ◽  
Pieter 't Hart ◽  
Pieter van Voorst Vader
Keyword(s):  
The Netherlands ◽  
North Sea ◽  
Phoca Vitulina ◽  
Research Centre ◽  
Halichoerus Grypus ◽  
Normal Behaviour ◽  
Delta Area ◽  
The North ◽  
The North Sea ◽  
Photophobic Reaction

AbstractThe Seal Rehabilitation and Research Centre (SRRC) in Pieterburen, The Netherlands, rehabilitates seals from the waters of the Wadden Sea, North Sea and Southwest Delta area. Incidental observations of albinism and melanism in common and grey seals are known from countries surrounding the North Sea. However, observations on colour aberrations have not been systematically recorded. To obtain the frequency of occurrence of these colour aberrations, we analysed data of all seals admitted to our centre over the past 38 years. In the period 1971-2008, 3000 common seals (Phoca vitulina) were rehabilitated, as well as 1200 grey seals (Halichoerus grypus). A total of five albinistic common seals and four melanistic grey seals were identified. This results in an estimated incidence of albinism in common seals of approximately 1/600, and of melanism in grey seals of approximately 1/300. The seals displayed normal behaviour, although in the albinistic animals, a photophobic reaction was observed in daylight.

An Innovative Self Installing Platform (SIP) Concept

2011 ◽  
Author(s):  
Frank Slangen ◽  
Wim Bal ◽  
Mark Riemers
Keyword(s):  
North Sea ◽  
Water Depth ◽  
Structural Design ◽  
Pile Foundation ◽  
Design Stage ◽  
Process Equipment ◽  
Design Elements ◽  
The North ◽  
The North Sea ◽  
Outside Diameter

Centrica Energy (formerly Venture) selected a self installing and re-usable platform concept (SIP) to develop their F3FA gas field in the Northern Part of the Dutch sector of the North Sea. On 6 February 2009 and following an initial FEED study, the contract was awarded to Heerema Fabrication Group (Main Contractor and Fabricator), in partnership with Iv-Oil & Gas (Designer and Procurer of process equipment) and SPT Offshore (Installation Contractor and Foundation Designer). The platform weighed in total 8,800 ton, including a 4,000 ton deck and 4,800 ton substructure including the suction pile foundation. The water depth at the F3FA site is 41m and the bottom of the cellar deck is located at 20m above LAT. The platform has an overall dimension of 63m × 45m footprint and protrudes some 90m above the seabed (excluding vent stack). The platform concept consists basically of a deck of 5 levels supported by 4 unbraced legs (3.25m outside diameter × 77m long) and founded on 4 huge suction piles (15m outside diameter × 13m deep). The platform is transported and installed using a large flat top barge (BOA 35 measuring 124m long × 31.5m wide × 8m high) and 3 tug boats (75, 90 and 183 ton bollard pull) for the tow from HFG’s yard in Vlissingen to the F3FA site in the Dutch sector of the North Sea. The leg lowering and deck lifting was achieved using 12× 900 ton strand jacks. The suction pile foundation was installed using 4× suction pumps. During the detailed design stage of the project, the concept design was subject to several elementary changes in the structural design. This had to do with the severe environment, the increased deck weight and water depth compared to the earlier utilisation of the concept. Fatigue and transport and installation issues had a significant impact on several key structural design elements. This complicated the deck-leg connections and several members in the truss deck. The deck leg connection was amended from a simple clamp connection in to a superbolt and sleeve connection at the top deck and a clamped and grouted connection at the cellar deck. In order to improve the stiffness of the legs, leg stiffening frames were placed on top of the suction piles. Due to the limited and slow roll & pitch response of the platform whilst on the BOA barge during tow, high seafastening forces were predicted. These high seafastening forces were transferred in to the barge using pinned seafastening arms. Water depth limitations and the additional leg stiffening frames necessitated to use a fairly high grillage structure of 6.5m high. All these items changed the deck construction towards a method obstructing completion of non-structural disciplines and changed the inshore mating operation of the substructure with that topside towards a complex lifting and fitting campaign. Despite these elementary design changes and some rigorous changes in the planning of the various activities, the contract schedule was achieved in time. The above efforts had an obvious effect on the managerial issues towards the project. It required a doubling of the manning levels and engineering issues of in some cases R&D nature. Despite all these challenges and complications, the platform left Vlissingen well ahead of time, on 18 August 2010, to set sail for the F3FA site. Upon arrival in the field, the weather deteriorated severely and the tow was forced to seek shelter in Rotterdam. Just before arrival in Rotterdam severe waves were encountered up to 6–7m maximum. Upon inspection in Rotterdam, the design proved to be resilient as no signs of damage were observed. Following 10 days waiting on weather the platform was towed to the field for the second time. Installation and lifting the deck to the top elevation was achieved within a record time of 2 days and 4 hours. Thereafter the platform hook-up team continued to work on the platform including completing the deck leg connections, such as installation of superbolts at the top deck level and clamp shells, rubber pads and grout at the cellar deck level. Further hook-up work consisted of hooking up the life support systems before arrival of the drill rig on 14th October 2010. The drilling of the first well was completed early January 2011 and first gas was introduced in to the pipeline system since week 4 of 2011.

Statistics of Greater Sea States

2011 ◽  
Author(s):  
Anne M. Fullerton ◽  
Thomas C. Fu
Keyword(s):  
Numerical Models ◽  
Ship Motions ◽  
Frequency Range ◽  
Sea State ◽  
The North ◽  
Spectral Models ◽  
Wave Heights ◽  
The North Sea ◽  
Computational Predictions ◽  
The Ideal

Accurate representations of seaway statistics are important for physical and computational predictions of ship motions. The spectra that are most typically used in these applications are the Pierson-Moskowitz or Bretschneider. While these spectra are useful for fully developed seas, the larger sea states (Sea State (SS) 7 and higher) are typically not fully developed. In these cases, other spectral models may be more appropriate. It is critical to ship motion prediction, for both physical and numerical models, to accurately capture the frequency range for the sea state of interest. Sea state statistics, including wave heights, periods, and spectral bandwidths from various buoys and a platform in the North Sea are collected and compared with statistics from lower sea states. The spectral data are then averaged to generate a typical spectrum under the measured conditions. These developed spectra are compared with the ideal spectra mentioned previously.

scholarly journals A Spatial Analysis of the Potentials for Offshore Wind Farm Locations in the North Sea Region: Challenges and Opportunities

2020 ◽  
Vol 9 (2) ◽  
pp. 96 ◽  
Author(s):  
Gusatu ◽  
Yamu ◽  
Zuidema ◽  
Faaij
Keyword(s):  
Protected Areas ◽  
North Sea ◽  
Water Depth ◽  
Wind Farm ◽  
Wind Farms ◽  
Offshore Wind ◽  
Offshore Wind Farms ◽  
The North ◽  
Challenges And Opportunities ◽  
The North Sea

Over the last decade, the accelerated transition towards cleaner means of producing energy has been clearly prioritised by the European Union through large-scale planned deployment of wind farms in the North Sea. From a spatial planning perspective, this has not been a straight-forward process, due to substantial spatial conflicts with the traditional users of the sea, especially with fisheries and protected areas. In this article, we examine the availability of offshore space for wind farm deployment, from a transnational perspective, while taking into account different options for the management of the maritime area through four scenarios. We applied a mixed-method approach, combining expert knowledge and document analysis with the spatial visualisation of existing and future maritime spatial claims. Our calculations clearly indicate a low availability of suitable locations for offshore wind in the proximity of the shore and in shallow waters, even when considering its multi-use with fisheries and protected areas. However, the areas within 100 km from shore and with a water depth above –120 m attract greater opportunities for both single use (only offshore wind farms) and multi-use (mainly with fisheries), from an integrated planning perspective. On the other hand, the decrease of energy targets combined with sectoral planning result in clear limitations to suitable areas for offshore wind farms, indicating the necessity to consider areas with a water depth below –120 m and further than 100 km from shore. Therefore, despite the increased costs of maintenance and design adaptation, the multi-use of space can be a solution for more sustainable, stakeholder-engaged and cost-effective options in the energy deployment process. This paper identifies potential pathways, as well as challenges and opportunities for future offshore space management with the aim of achieving the 2050 renewable energy targets.

The Selandian (Paleocene) mollusc fauna from Copenhagen, Denmark: the Poul Harder 1920 collection

2001 ◽  
pp. 1-85
Author(s):  
Kaj Ingemann Schnetler
Keyword(s):  
New Species ◽  
Water Depth ◽  
Historical Context ◽  
Fine Grained ◽  
The North ◽  
First Occurrence ◽  
Near Shore ◽  
The North Sea ◽  
Molluscan Fauna ◽  
Fine Grained Sand

NOTE: This monograph was published in a former series of GEUS Bulletin. Please use the original series name when citing this monograph. Schnetler, K. I. (2001). The Selandian (Paleocene) mollusc fauna from Copenhagen, Denmark: the Poul Harder 1920 collection. Geology of Denmark Survey Bulletin, 37, 1-85. https://doi.org/10.34194/dgub.v37.5021 A detailed study has been made of the molluscan fauna in the material collected by Poul Harder in 1920 from the classical Danish early Selandian (Late Paleocene) locality in the Lellinge Greensand at Sundkrogen (the harbour of Copenhagen). A description is also given of the now submerged locality.The Harder collection, which has remained virtually unstudied for more than 75 years, is discussed in the interesting historical context that it was not included in the monograph on the Paleocene of Copenhagen by J.P.J. Ravn in 1939. Ravn's study was based on material collected the same year from Sundkrogen by A. Rosenkrantz, and on material collected in the thirties from other localities in the Copenhagen area. Some material collected by A. Rosenkrantz and others, but not dealt with by J.P.J. Ravn, is also included in the present study. The long-lasting controversy about publication rights relating to the Sundkrogen material is recalled.Twenty-seven new species are introduced, viz. Portlandia (Yoldiella) nielseni n. sp., Plicatula selandica n. sp., Laternula (Laternulina) ravni n. sp., Dentalium (Dentalium) sundkrogensis n. sp., Solariella (Solariella) ravni n. sp., Solariella (Solariella) hauniensis n. sp., Teinostoma (Teinostoma) ledoni n. sp., Entomope kirstineae n. sp., Harrisianella subglabra n. sp., Bittium (Bittium) oedumi n. sp., Cerithiopsidella (Vatopsis) rasmusseni n. sp., Seila (Notoseila) heilmannclauseni n. sp., Seila (Notoseila) anderseni n. sp., Thereitis weinbrechti n. sp., Cirsotrema (Cirsotrema) hauniensis n. sp., Opalia (Pliciscala) thomseni n. sp., Charonia (Sassia) danica n. sp., Siphonalia arlejansseni n. sp., Astyris (Astyris) lappanni n. sp., Streptolathyrus danicus n. sp., Streptolathyrus lemchei n. sp., Cancellaria (sensu lato) jakobseni n. sp., Pseudocochlespira rosenkrantzi gen. et sp. n., Actaeopyramis marcusseni n. sp., Chrysallida (Parthenina) peterseni n. sp., Syrnola (Syrnola) granti n. sp. and Cingulina harderi n. sp. Within the Turridae, Pseudocochlespira n. gen. is established.A total of 182 taxons are listed. Of these, 36 are new for the Lellinge Greensand, and 60 have not previously been recorded from Sundkrogen. The study demonstrates that several genera have their first occurrence datum in the Selandian. The Selandian mollusc fauna from Sundkrogen and elsewhere in the Copenhagen area has no equivalent in the North Sea Basin, but faunas from boulders of Selandian age from the south-eastern part of Denmark and the southern part of Sweden demonstrate affinities with the Sundkrogen fauna, whereas the fauna from the Kerteminde Marl demonstrates a lesser degree of affinity.The palaeoenvironment is interpreted as a transgression of the Selandian Sea with erosion of the underlying Danian sediments. The near-shore environment was followed by gradually increasing water depth, resulting in deposits of fine-grained sand and finally dark clay. The dark clay was probably deposited in a deep inlet from the eastern margin of the Selandian Sea.

Using a Dacon Scoop to Recover a Loaded Liferaft at Sea

2013 ◽  
Author(s):  
Robert Brown ◽  
Kerri-Ann Evely ◽  
Graham Small ◽  
Scott MacKinnon
Keyword(s):  
North Sea ◽  
Human Factor ◽  
Effective Means ◽  
Field Trials ◽  
Safe Haven ◽  
Eastern Canada ◽  
The North ◽  
Wave Heights ◽  
The North Sea ◽  
Significant Wave Heights

Service and supply vessels that perform standby duties in the offshore sector are equipped with a variety of resources with which to perform rescue at sea. For light to moderate sea conditions, techniques currently understood and practiced tend to involve using a fast rescue craft (FRC) to rescue survivors and subsequently transfer them to a safe haven (often a standby vessel). Rescuing evacuees in higher, more challenging sea states, however, is difficult given that it can be unsafe to launch and recover FRCs in such conditions. For these cases, many standby vessels in Eastern Canada and the North Sea are equipped with a device called a Dacon Scoop. The Dacon Scoop is a 6 to 8m semi-rigid net that is deployed directly from the side of the standby vessel and designed to rescue people directly from the water. While not a conventional use, it has been suggested that the scoop could also be used to recover small rescue craft (life rafts, lifeboats and fast rescue craft) at sea. Although life rafts provide occupants with some protection from the elements, there are still issues that can make it less than desirable to remain inside for extended periods of time if an effective means of system recovery is available. This paper presents the findings of research carried-out to determine if it is safe to use a Dacon Scoop to recover a loaded liferaft. The research trials made use of a loaded inflatable 25 person davit launched life raft and two different standby vessels 75m in length. A total of 34 tests were carried out over three days in significant wave heights up to 3.7m. Recommendations are given in the context of a human factor assessment related to the procedures, equipment and field trials experiences.

scholarly journals WAVE GROUP FORMATION AMONG STORM WAVES

1974 ◽  
Vol 1 (14) ◽  
pp. 7 ◽  
Author(s):  
H. Rye
Keyword(s):  
North Sea ◽  
Group Formation ◽  
Weather Conditions ◽  
Wave Group ◽  
Average Correlation ◽  
The North ◽  
Storm Waves ◽  
Stormy Weather ◽  
Wave Heights ◽  
The North Sea

Wave data obtained m the North Sea for stormy weather conditions are analyzed to determine the extent of wave group formation among large waves; i.e. the number of large waves succeeding each other in one single run. Three periods associated with the passage of high sea states are examined. The average correlation between succeeding wave heights is found to be +0.2H, which indicates that wave heights do have a "memory". Wave group formations are found to be more pronounced when the sea is growing than decaying. The average lengths of wave runs are calculated.

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