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1.
风机基础作为海上风机整体结构的重要组成部分,承受着上部风机所受到的风浪流荷载,并且对风机的安全性及可靠性至关重要。吸力式桶形基础由于其安装简单和可重复利用等优点,在海洋平台基础中得到了广泛应用,并逐步应用于海上风机基础中。但由于海上风机与海洋平台在海洋环境中的荷载工况有一定的差别,仍需要通过对其承载特性研究现状进行全面认识,以实现吸力式桶形基础在海上风机基础中的可靠应用。文中通过总结和评价现有研究对桶形基础在不同土体条件以及荷载条件下进行试验及数值模拟分析得到的研究结果,综述了静荷载和循环荷载作用下砂土和黏土中的吸力式桶形基础的承载特性研究现状,以及海上风机吸力式桶形基础的相关研究。文章展望了目前应用于海上风机基础的桶形基础仍缺乏的研究,为海上风机吸力式桶形基础的可靠应用及后续研究提供重要参考。 相似文献
2.
A study was conducted to understand the mechanisms driving observed subtidal variability in the stratification of Saldanha Bay, located in the southern Benguela system. It was found that the 6–8 day period variability in bay stratification was caused by the inflow and outflow of cold upwelled water driven by changing baroclinic pressure gradients between the coastal and bay domains. The direction and magnitude of the pressure gradients were governed by coastal upwelling activity and a lag in the response of the bay to changes in density structure in the coastal ocean. When the pressure gradients were bayward and cold water was being driven into the bay the cycle was termed to be in an ‘ active phase ’ and the reverse was termed the ‘ relaxation phase ’. The upwelling-favourable equatorward wind stress impacted the bay stratification in two ways: on the regional scale, wind drives upwelling and governs the inflow–outflow of cold upwelled bottom water, which strengthens stratification; conversely, on the local bay scale, wind drives vertical mixing, which weakens stratification. A four-phase model is used to describe the observed variability in stratification in the bay. The associated density-driven exchange flows are capable of flushing the bay in 6–8 days, about one-third of the time for tidal exchange alone (c. 25 days). These inflows of cold bottom water are ecologically critical as they supply nutrients to the bay and thus impose a control on new production within the bay environment. Further ecological implications of this bay–ocean exchange include export of phytoplankton new production to the coast, limitation of the risk of harmful algal blooms (HABs) and the division of the system into two distinct ecosystems (bay and lagoon). 相似文献
3.
参考英国的Kincardine风机采用的新式的Semi-Spar概念,结合spar式基础和半潜式基础的特点,提出了一种新式海上浮式风机平台模型,并基于三维势流理论,利用AQWA软件进行水动力计算,验证新式平台可靠性。分析了在风、浪、流荷载联合作用下,锚链竖向夹角、系缆数量对风机浮式平台运动性能和系泊张力的影响,对系泊系统进行优化,并验证极端工况下的可靠性。结果证明风机平台水平运动和纵摇运动幅值较小,但垂荡幅值略大,而通过减小锚链竖向夹角可以控制平台运动响应幅值,增加系缆数量可以同时减小系泊张力大小。计算结果证明了新型Semi-Spar式海上风机平台可行性,为浮式风机平台及系泊系统的设计提供参考。 相似文献
4.
The co-location of offshore windfarms and decapod fisheries in the UK: Constraints and opportunities
《Marine Policy》2014
The offshore wind sector in the UK is expanding rapidly and is set to occupy significant areas of the coastal zone, making it necessary to explore the potential for co-location with other economic activities. The presence of turbine foundations introduces hard substrates into areas previously dominated by soft sediments, implying that artificial reef effects may occur, with potential benefits for fisheries. This review focuses on the possibilities for locating fisheries for two commercially important decapods, the brown crab Cancer pagurus and the European lobster Homarus gammarus, within offshore wind farms.Existing understanding of habitat use by C. pagurus and H. gammarus suggests that turbine foundations have the potential to act as artificial reefs, although the responses of these species to noise and electromagnetic fields are poorly understood. Offshore wind farm monitoring programmes provide very limited information, but do suggest that adult C. pagurus associate with turbine foundations, which may also serve as nursery areas. There was insufficient deployment and monitoring of rock armouring to draw conclusions about the association of H. gammarus with offshore wind farm foundations. The limited information currently available demonstrates the need for further research into the ecological and socio-economic issues surrounding fishery co-location potential. 相似文献
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Grgory Beaugrand 《Progress in Oceanography》2004,60(2-4):245
This paper focuses on the ecosystem regime shift in the North Sea that occurred during the period 1982–1988. The evidence for the change is seen from individual species to key ecosystem parameters such as diversity and from phytoplankton to fish. Although many biological/ecosystem parameters and individual species exhibited a stepwise change during the period 1983–1988, some indicators show no evidence of change. The cause of the regime shift is likely to be related to pronounced changes in large-scale hydro-meteorological forcing. This involved activating of complex intermediate physical mechanisms which explains why the exact timing of the shift can vary from 1982 to 1988 (centred around two periods: 1982–1985 and 1987–1988) according to the species or taxonomic group. Increased sea surface temperature and possibly change in wind intensity and direction at the end of the 1970s in the west European basin triggered a change in the location of an oceanic biogeographical boundary along the European continental shelf. This affected both the stable and substrate biotope components of North Sea marine ecosystems (i.e. components related to the water masses and components which are geographically stable) circa 1984. Large-scale hydro-climatic forcing also modified local hydro-meteorological parameters around the North Sea after 1987 affecting the stable biotope components of North Sea ecosystems. Problems related to the detection and quantification of an ecosystem regime shift are discussed. 相似文献
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A coupled discontinuous–continuous Galerkin (DG–CG) shallow water model is compared to a continuous Galerkin generalized wave-continuity equation (GWCE) based model for the coastal ocean, whereby local mass imbalance typical of GWCE-based solutions is eliminated using the coupled DG–CG approach. Two mass imbalance indicators for the GWCE-based model are presented and analyzed. The indicators motivate discussion on the suitability of using a GWCE-based model versus the locally conservative coupled DG–CG model. Both realistic and idealized test problems for tide, wind, and wave-driven circulation form the basis of the study. For the problems studied, coupled DG–CG solutions retain the robustness of well-documented solutions from GWCE-based models and also capture the dynamics driven by small-scale, highly advective processes which are problematic for GWCE-based models. Issues associated with the coupled DG–CG model are explored, including increased cost due to increased degrees of freedom, the necessary application of slope limiters, as well as the actual coupling process. 相似文献
9.
A coupled wave–tide–surge model has been developed in this study in order to investigate the effect of the interactions among tides, storm surges, and wind waves. The coupled model is based on the synchronous dynamic coupling of a third-generation wave model, WAM cycle 4, and the two-dimensional tide–surge model. The surface stress, which is generated by interactions between wind and wave, is calculated by using the WAM model directly based on an analytical approximation of the results using the quasi-linear theory of wave generation. The changes in bottom friction are created by the interactions between waves and currents and calculated by using simplified bottom boundary layer model. In consequence, the combined wave–current-induced bottom velocity and effective bottom drag coefficient were increased in the shallow waters during the strong storm conditions. 相似文献
10.
A. Calabrese J.R. MacInnes D.A. Nelson R.A. Greig P.P. Yevich 《Marine environmental research》1984,11(4):253-274
The purpose of this study was to determine the long-term accumulation of either silver or copper from low concentrations in seawater by blue mussels, Mytilus edulis. Mussels raised from eggs in the laboratory to the age of 2·5 months (approximately 4·5 mm in length) were continuously exposed to 0, 1, 5 and 10μg/liter of either silver (nitrate) or copper (chloride) and sampled at 12, 18 and 21 months for growth studies, measurements of metal accumulation and histopathological examination.Whole-body soft tissues were analyzed for the presence of both silver and copper, as background levels of copper in the incoming seawater averaged 2–4 μg/liter. Mussels exposed to silver had accumulated significant amounts of silver only at the highest test concentration (10 μg/liter Ag) after 12 months, but at 18 and 21 months significant levels were accumulated at all three test concentrations. Mussels exposed to copper accumulated significant amounts of copper at 5 and 10 μg/liter Cu after all three sampling periods, but not at 1μg/liter. Silver-exposed animals also accumulated significantly greater amounts of copper than control animals.In a comparative study, field-collected juvenile mussels (approximately 16·1 mm in shell length) and adult mussels (approximately 53·4 mm in shell length) were exposed for 12 months to 0, 5, 25 and 50 μg/liter silver only and subsequently sampled for metal-accumulation analyses and growth measurements. Juvenile mussels accumulated significant amounts of silver at all test concentrations, with the exception of mussels exposed to 5 μg/liter Ag for 6 months. Copper accumulation in the silver-exposed juveniles was significant only at 50 μg/liter Ag after 6 months, but at all test concentrations after 12 months. Adult mussels exposed to silver accumulated significant levels of both silver and copper, but at somewhat lower levels than juveniles.In the growth study, silver had no effect on laboratory reared mussels at the highest concentration of 10 μg/liter tested, whereas copper at 10 μg/liter did appear to affect growth as early as 4 months after the start of experimental exposure. Field-collected juvenile mussels did show inhibition in growth after 6 months' exposure to 25 and 50 μg/liter Ag, with some growth occurring after 12 months. Adults also showed inhibition in growth after 6 months but not at 12 months.Histopathological examination of mussels exposed to either 5 or 10 μg/liter of copper for 18 months showed changes in the digestive diverticula, gastrointestinal tract, reproductive tract and muscle tissues. These changes were more noticeable in mussels exposed to 5 μg/liter Cu than in those exposed to 10 μg/liter. Mussels exposed to silver for 21 months showed yellowish to black particulate deposition in the basement membrane and connective tissue of the various organs and tissues. Silver deposition increased with increasing test concentration. 相似文献
11.
Prediction of wave parameters by using fuzzy logic approach 总被引：2，自引：0，他引：2
The purpose of this study is to investigate the relationship between wind speed, previous and current wave characteristics. It is expected that such a non-linear relationship includes some uncertainties. A fuzzy inference system employing fuzzy IF–THEN rules has an ability to deal with ill-defined and uncertain systems. Compared with traditional approaches, fuzzy logic is more efficient in linking the multiple inputs to a single output in a non-linear domain. In this paper, a sophisticated intelligent model, based on Takagi–Sugeno (TS) fuzzy modeling principles, was developed to predict the changes in wave characteristics such as significant wave height and zero up-crossing period due to the wind speed. Past measurements of significant wave height values and wind speed variables are used for training the adaptive model and it is then employed to predict the significant wave height amounts for future time intervals such as 1, 3, 6 and 12 h. The verification of the proposed model is achieved through the wave characteristics time series plots and various numerical error criterias. Also the model results were compared with classical Auto Regressive Moving Average with exogenous input (ARMAX) models. For the application of the proposed approach the offshore station located in the Pacific Ocean was used. 相似文献
12.
Biotic consequences of a shift in invertebrate ecosystem engineers: Invasion of New Zealand rocky shores by a zone‐forming ascidian 
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下载免费PDF全文 The pervasive effects of invasive ecosystem engineers, that is those species that modify their environment, are well documented, but rarely have the broader impacts of one foundation invertebrate species being replaced by another been examined. In New Zealand, green‐lipped mussels, Perna canaliculus, commonly dominate wave‐exposed rocky shores. The recent appearance of an invasive ecosystem engineer, the ascidian Pyura doppelgangera, at the very northern tip of New Zealand now threatens to exclude these bivalves from this habitat. Here, we report major shifts in assemblages associated with the invader and chronicle its continued spread. We examined epibiota associated with clumps of mussels and clumps of Pyura from two rocky shore habitats—pools and emergent substrata at two locations. We detected some differences in species richness in biota associated with the two foundation species, but faunal abundance only differed between the locations. These minor changes were dwarfed by the shift in species composition within clumps of each foundation species. Molluscs, particularly gastropods, and crustaceans dominated the assemblage within mussels. In contrast, tubicolous polychaetes dominated the fauna associated with the ascidian. Sessile epifauna, notably barnacles and calcareous tube‐dwelling polychaetes, were common on mussels, but never encountered on the ascidian. Multivariate analysis revealed marked dissimilarity (>80%) between the characteristic mussel and ascidian faunas with virtually no overlap. This biotic shift overshadowed any differences between habitats and locations. The broader implications of these faunal shifts for local and regional patterns of biodiversity, as well as ecosystem function, remain unclear, but deserve further attention. 相似文献
13.
Little is known about the effects of offshore energy installations on the marine environment, and further research could assist in minimizing environmental risks as well as in enhancing potential positive effects on the marine environment. While biofouling on marine energy conversion devices on one hand has the potential to be an engineering concern, these structures can also affect biodiversity by functioning as artificial reefs. The Lysekil Project is a test park for wave power located at the Swedish west coast. Here, buoys acting as point absorbers on the surface are connected to generators anchored on concrete foundations on the seabed. In this study we investigated the colonisation of foundations by invertebrates and fish, as well as fouling assemblages on buoys. We examined the influence of surface orientation of the wave power foundations on epibenthic colonisation, and made observations of habitat use by fish and crustaceans during three years of submergence. We also examined fouling assemblages on buoys and calculated the effects of biofouling on the energy absorption of the wave power buoys. On foundations we demonstrated a succession in colonisation over time with a higher degree of coverage on vertical surfaces. Buoys were dominated by the blue mussel Mytilus edulis. Calculations indicated that biofouling have no significant effect in the energy absorption on a buoy working as a point absorber. This study is the first structured investigation on marine organisms associated with wave power devices. 相似文献
14.
Northeasters are storms that affect the Chesapeake Bay area more frequently, last for longer periods and impact larger areas than hurricanes. Their impacts on storm surge development and the water exchange between estuary and subestuaries (tributaries) in the Bay vary from one event to another. In this study, three different northeaster events were selected based on their tracks when passing through the Chesapeake Bay area. An unstructured grid finite volume model ELCIRC was utilized to examine the response of the water level of the Chesapeake Bay to three selected northeasters, and the barotropic subtidal water exchanges between the tributaries and the estuary in the Bay. Model sensitivity tests were conducted to examine various effects induced by, for example, tide–surge interaction, open boundary condition, river inflow, wetting-and-drying of the low-lying land area and the usage of 2-D or 3-D mode. The results show that excluding tide–surge interaction did not deteriorate the model performance in the lower Bay but it increased the model inaccuracy in the upper Bay and in the tributaries; using radiation boundary condition decreased the sea level variation in the Bay without appropriately specifying incoming wave; excluding wetting-and-drying of low-lying land area reduced the volume flux by approximately 5%; and using 3-D mode generally increased the water level variation in the Bay. The model predicted storm surges well for three northeaster events. Further diagnostic experiments show that the relative importance of the local and remote winds in generating storm surges in the Bay varied with different northeasters. The inverse barometeric effect played an important role in inducing storm surges for two selected northeasters. The interaction between the tributaries and the Bay proper is considerable. The impacts of the remote wind and Bay wind can be much larger than that of the tributary wind and, thus, control the hydrodynamics and mass transport in the tributaries. The Bay wind and tributary wind effects are largely affected by the wind direction and wind phase, and geographic locations of the tributaries in the Bay. The tributary wind can be dominant over the remote wind and Bay wind effects when the local wind stress and barometric pressure changes are large. 相似文献
15.
《Marine Policy》2017
The expansion of offshore wind farms (OWFs) is likely to increase conflict with other marine users as different sectors compete for space. There may also be positive interactions, as the artificial reef effects from energy infrastructure have the potential to sustain and enhance fishing opportunities. Recreational sea angling is an important sector within the UK but the experiences and opinions of UK sea anglers with respect to OWFs have not been documented. To address this, an online survey was undertaken with recreational anglers around the UK (n=199). Respondents represented a range of socio-demographic and angling characteristics, although male, more frequent and older fishers as well as club members were over-represented compared to a 2012 national survey. One quarter of the respondents had fished around the perimeter of or within an OWF, most on multiple occasions, and 73% of those who had not expressed a willingness to do so in future. Anglers reported both positive and negative effects on catch success when fishing near or within OWFs compared to their experiences of the same site prior to OWF development. Outcomes for individual species were also mixed. Anglers recognised the potential artificial reef effects of OWFs and their role as a “safe haven”, particularly due to the exclusion of commercial fishers. Negative perceptions included restricted access, harm to marine wildlife, and visual impact. There is little evidence that OWFs will have a significant economic impact on recreational fishing, as most anglers are unlikely to change their behaviour in response to future developments. 相似文献
16.
Fatty acid composition of phytoplankton, settling particulate matter and sediments at a sheltered bivalve aquaculture site 总被引：5，自引：0，他引：5
Fatty acid biomarkers were used to investigate the biogeochemistry of a former blue mussel (Mytilus edulis) aquaculture site in a shallow, sheltered cove in northeastern Newfoundland. High levels of polyunsaturated fatty acids (PUFA) in net-tow and sediment trap samples indicated a substantial phytoplankton source of organic matter, and fluctuations in specific fatty acid biomarkers reflected the changing abundances of diatoms and dinoflagellates. In comparison, sediments contained very low levels of PUFA (<15%) and were dominated by terrestrial and bacterial markers. In a separate study, blue mussels were grown at this closed site, providing the opportunity to examine the relationship between lipid supply, as recorded by net-tow and trap samples, and bivalve requirements. The average plankton fatty acid composition throughout the year agreed well with that of the adult blue mussels, suggesting that fatty acids were provided in proportions very similar to the bivalves' requirements. The fatty acid composition of the blue mussels was typical of those collected elsewhere, with PUFA proportions near 50%. However, examination of fatty acid data of plankton sampled in other areas revealed that the plankton in the current study may have been unusual in providing fatty acids at levels required by the bivalves. 相似文献
17.
Although the Danish Wadden Sea is of international importance for several bird species, large-scale blue mussel Mytilus edulis fishing took place from 1984–1987, ceasing thereafter due to low mussel stocks. Mussel fishing removes much of the blue mussel biomass, especially larger individuals. Hence we predict that intensive mussel fishing will affect their predators, such as the Eider Somateria mollissima, which is predominantly a blue mussel feeder by, 1) reducing the amount of blue mussels in their diet relative to alternative prey items, 2) exploitation of smaller blue mussel shell classes, 3) loss of body condition, 4) changing feeding distribution to aggregate to the remaining mussel stocks, and 5) decreasing numbers. Before winter 1986/87 blue mussel biomass was estimated at 40,600 tons, decreasing to 15,400 tons in 1987/88 due to mussel fishery. We collected Eiders in both periods to monitor their diet and body mass and used aerial surveys to determine changes in numbers and distribution. Between the two periods, blue mussels declined in the Eiders diet, numbers of Eiders with empty stomachs increased and the mean length of blue mussel taken by Eiders decreased. Eider body condition declined from 1986/87 to 1987/88, mostly the result of the reduction in numbers of individuals with blue mussel remains in their gizzards and in better body condition compared to those taking alternative food items or having empty gizzards. Eiders shifted their distribution from the southern part of the Danish Wadden Sea to the northern part, where the remaining blue mussel stocks were situated. Eider numbers were lowest in 1987/88, the year of lowest blue mussel stocks. We conclude that intensive mussel fishery affected the Eider's diet, reduced their body condition and affected distribution and abundance. The results also showed that availability of blue mussels may have a key role in building up and maintaining body condition in Eiders during winter. 相似文献
18.
Because offshore wind energy development is fast growing in Europe it is important to investigate the changes in the marine environment and how these may influence local biodiversity and ecosystem functioning. One of the species affected by these ecosystem changes is Atlantic cod (Gadus morhua), a heavily exploited, commercially important fish species. In this research we investigated the residency, site fidelity and habitat use of Atlantic cod on a temporal scale at windmill artificial reefs in the Belgian part of the North Sea. Acoustic telemetry was used and the Vemco VR2W position system was deployed to quantify the movement behaviour. In total, 22 Atlantic cod were tagged and monitored for up to one year. Many fish were present near the artificial reefs during summer and autumn, and demonstrated strong residency and high individual detection rates. When present within the study area, Atlantic cod also showed distinct habitat selectivity. We identified aggregation near the artificial hard substrates of the wind turbines. In addition, a clear seasonal pattern in presence was observed. The high number of fish present in summer and autumn alternated with a period of very low densities during the winter period. 相似文献
19.
A coupled wave–tide–surge model has been established in this study in order to investigate the effect of tides, storm surges, and wind waves interactions during a winter monsoon on November 1983 in the Yellow Sea. The coupled model is based on the synchronous dynamic coupling of a third-generation wave model, WAM-Cycle 4, and the two-dimensional tide–surge model. The surface stress generated by interactions between wind and waves is calculated using the WAM-Cycle 4 directly based on an analytical approximation of the results obtained from the quasi-linear theory of wave generation. The changes of bottom friction factor generated by waves and current interactions are calculated by using simplified bottom boundary layer model. The model simulations showed that bottom velocity and effective bottom drag coefficient induced by combination of wave and current were increased in shallow waters of up to 50 m in the Yellow Sea during the wintertime strong storm conditions. 相似文献
20.
A simplified method is introduced to obtain the fundamental frequency of offshore wind turbines supported by monopile foundations. Soil-pile interaction is modeled based on Winkler approach and concept of beam on elastic foundation. The soil is considered to have linearly varying modulus of subgrade reaction along depth which is a typical assumption for cohesionless soils. Rayleigh method which is based on conservation of total energy of the system is utilized. Firstly the natural frequency of the system with rigid pile is derived and then an innovative procedure is introduced to take pile flexural stiffness into consideration. Comparison between results of the present method with those of a numerical FE model for a typical 2 MW wind turbine structure shows excellent agreement for rigid pile and flexible pile with small value of slenderness ratio. The agreement is also good for flexible pile with higher slenderness ratios. A parametric study is carried out to investigate the effect of important parameters of foundation including pile slenderness ratio, pile aspect ratio and pile mass on the system natural frequency. 相似文献