Liu G.,National University of Singapore |
Chen H.,Marine Design and Research Institute of China |
Liu D.,Harbin Engineering University |
Khoo B.C.,National University of Singapore
Bulletin of the Seismological Society of America | Year: 2010
Wave propagation in a half-space with complex surface configuration is often encountered in fields like seismology and ocean engineering. This article presents a theoretical study of multiple scattering of SH waves by two hills of different geometries (a triangle and a semicircle) on a solid half-space. The standing waves in the triangular and semicircular hills are constructed by the fractional-order Bessel function method and Fourier integral transform method, respectively. The unknown coefficients of the standing waves are determined via the region-matching method. It is shown that the apexes of the hills are very sensitive to the external dynamic load because of multiple incidences; in particular, the apex of the triangular hill exhibiting maximum amplitude is most susceptible to the external load. Furthermore, the effect of the interaction between the triangular and semicircular hills is evaluated. It is found that the amplitudes on the showdown zone that connects the two hills have been largely amplified due to the interaction between the two hills. The mutual interaction between the hills should not be neglected if the distance between them is less than O(100) times the typical dimension of the hill.
Ni C.-B.,Shanghai JiaoTong University |
Zhu R.-C.,Shanghai JiaoTong University |
Miao G.-P.,Shanghai JiaoTong University |
Fan S.-M.,Marine Design and Research Institute of China
Shuidonglixue Yanjiu yu Jinzhan/Chinese Journal of Hydrodynamics Ser. A | Year: 2010
A method for ship resistance prediction based on CFD computation is outlined, with ship form factor obtained by solving the viscosity resistance of double-model in turbulence flow theory and the wave making resistance in ideal flow theory. Comparing with the experimental results of series-60 and KCS advancing with different speeds, the new method of ship resistance prediction is economical, practical and meets the engineering needs.
Liu S.M.,Ocean University of China |
Li R.H.,Ocean University of China |
Zhang G.L.,Ocean University of China |
Wang D.R.,Marine Design and Research Institute of China |
And 4 more authors.
Marine Chemistry | Year: 2011
Biogeochemical observations were carried out in the Wenchanghe and Wenjiaohe Estuary, Bamen Bay and Gaolong Bay during 2006-2009 to understand the nutrient dynamics of these areas and their relationship with the sustainability of the ecosystems in the coastal areas of Eastern Hainan Island and its adjacent South China Sea. Nutrients in river/estuary waters, groundwater, aquaculture effluents and rainwater samples were analyzed using spectrophotometry. Nutrient levels in the tropical Wenchanghe and Wenjiaohe show a wide range of variation depending on the system, nutrient element and season. These two rivers are enriched with DIN and depleted in PO4 3- with the DIN:PO4 3- ratios varied from 60 to 411. In the rivers, TDP was mainly composed of DOP, representing ~65%. DON accounted for 40% of TDN in the Wenchanghe and 76% of that in the Wenjiaohe. Dissolved silicate levels in the Wenjiaohe and Wenchanghe were lower than average levels in tropical systems.Nutrients in the Wenchanghe and Wenjiaohe Estuary behave either conservatively or non-conservatively depending on the element being considered and the season. Based on observations of nutrients in various aquatic environments, a simple steady-state mass-balance box model was employed to assess nutrient budgets in the estuary system. Nutrients in the studied system were mostly from riverine input, groundwater discharge and aquaculture effluents. The nutrients exported in the studied system are largely confined to the immediate estuaries. The typhoon-induced runoff of terrestrial rainwater can not only increase nutrient inputs to the coastal ecosystem but can also result in nutrient imbalance, affecting phytoplankton production and composition. © 2011 Elsevier B.V.
Zhang J.,East China Normal University |
Wang D.R.,Marine Design and Research Institute of China |
Jennerjahn T.,Leibniz Center for Tropical Marine Ecology |
Dsikowitzky L.,Leibniz Center for Tropical Marine Ecology |
Dsikowitzky L.,RWTH Aachen
Continental Shelf Research | Year: 2013
The structure and function of coastal ecosystems is affected by land-based human activities, including changes in water, sediment and pollutant input, as well as land reclamation in coastal areas. Many coastal areas can be considered over-stressed systems as a whole, the ecosystem services of which are strongly impaired. This is particularly important in tropical regions, where the coastal zone is under the influence of a strong climate variability including monsoons and frequent extreme weather events, such as typhoons. During the past decades the continuous development of Hainan's coastal zone and its hinterland, in combination with episodic natural events (e.g., typhoons), caused environmental changes in its coastal ecosystems. However, little is known on the consequences of environmental changes for the biogeochemistry and ecology and, hence, the natural resources of the Hainan coastal ecosystems. The Sino-German inter-disciplinary LANCET (land-sea interactions along coastal ecosystems of tropical China: Hainan) project was designed to address these issues on a local to regional scale and at the same time, to contribute to the global data base in which this type of information from tropical regions is still under-represented. The results obtained from LANCET have been delivered to the local government for an adaptive management at the ecosystem level, and the knowledge is believed to be relevant to other studies of tropical and coastal regions. © 2013 Elsevier Ltd.
Krumme U.,Leibniz Center for Tropical Marine Ecology |
Krumme U.,Johann Heinrich Von Thunen Institute |
Wang T.C.,Leibniz Center for Tropical Marine Ecology |
Wang D.R.,Marine Design and Research Institute of China
Continental Shelf Research | Year: 2013
In the Asia-Pacific region, the increasing demand for low value/trash fish as feed for mariculture drives unsustainable fisheries on already overexploited marine resources. The mariculture demand may also affect artisanal nearshore fisheries operating in shallow nursery grounds, e.g., lift net fisheries, but little is known about how they work. We describe the stationary lift net artisanal fishery on the East coast of Hainan Island (northern South China Sea). A trapezoidal blanket net (mean surface area: 478m2), stretched between four upright poles at the corners, is lowered and lifted via a rope system from a tower by a single fisher. In 2009 ~200 households depended on 288 lift nets, 82% of which were located in the Wenchang/Wenjiao estuary. The number of lift nets decreased by 15% from 2007 to 2009. Presently, it is mainly an early retirement activity of fishers with a median age of 52 years and younger men rarely enter the fishery due to low catch rates. However, not one fisher would stop fishing even at 50% hypothetical decline in catch - due to lack of alternatives. Mean catch weight per fishing day is 12kg (range: 0-1.7t). In the past, the entire catch was used as food. Presently, an average of 52% of the catch is sold as feed to local pond and floating net cage mariculturists who, subsequently, supply the live food trade to markets as far as Hong Kong. Larger dead fishes are sold at village markets or at Qinglan harbor and are locally or regionally consumed. The density of lift-net operation is highest around the Wenchang/Wenjiao lagoon due to the presence of an extensive sheltered, shallow subtidal area in proximity to mariculture and export markets in Qinglan. Thus, the modern mariculture demand for low value/trash fish supports the continuation of an ancient artisanal fishery despite severe resource depletion. The existence of similar lift nets in Vietnam points to an exchange in the artisanal fishing knowledge between Vietnam and Hainan. Additionally, interviews with lift-net fishers provided valuable information on historical changes in the lagoon system (e.g., mangrove loss, sedimentation, pollution, interaction with other fishing activities), and suggest that the summer fishing moratorium of the offshore fleet leads to increased fishing pressure on inshore resources by artisanal fisheries. In conclusion, we provide suggestions for management of the inshore water resources and their artisanal fisheries. © 2012 Elsevier Ltd.
Song J.,Marine Design and Research Institute of China
Ship Building of China | Year: 2015
This paper elaborates some key technology aspects in general design of FLNG, which is a floating LNG production unit together with natural gas pre-treatment, liquification, storage and offloading system. Hull's main dimension, lines and typical loading conditions are studied, and then a FLNG with main dimension of 250, 000 m3 is provided to get good hull motion and assure high efficiency of topside production system. Characteristics of LNG cargo containment system for FLNG unit are described, and membrane type of tank is compared with SPB independent tank. Seawater lift submersible electric pump system is proposed as a cooling seawater supply system for topside liquification unit. ©, 2015, Editorial Office of Shipbuilding of China. All right reserved.
Zhao G.,Marine Design and Research Institute of China
Materials China | Year: 2014
Just like the structure in the aerospace which is defined as aircraft internationally, is divided into aviation and astronavigation, the author divides the structure in the sea which is collectively named as marine steel structure into two branches, i.e. ship and marine engineering. The author focuses on marine and offshore oil and gas drilling equipment mainly from the perspective of the shipbuilding industry, describes the features, design criteria and steel selection principles of marine steel structures, and lists the steel amount of typical transport ships and the carriers of offshore oil and gas engineering plants, as well as the mount of the typical steel pipes on the offshore oil and gas engineering plants. The author tells about the special requirements for Extra High Strength Steel and Special Steel(including Low Temperature Steel, Corrosion-Resistant Steel, Lamellar-Tearing-Resistance Steel, Welding-Crack-Resistance Steel, Cast and Low Magnetic Steel mainly) on carriers. The author also introduces the applications of steel pipe on marine steel structures. For becoming the powerful country on shipbuilding and marine industry, Chinese metallurgical industry is to contribute. The author also suggests that Chinese shipbuilding steel market should rationalize the system and communication needs, stand out essentials and get close to projects.
Cao R.S.,Qingdao University of Science and Technology |
Fang Y.Y.,Qingdao University of Science and Technology |
Wang L.,Marine Design and Research Institute of China
Applied Mechanics and Materials | Year: 2014
The wind load acted on ship mast at different wind angles of large Reynolds number is numerically simulated in this paper. CFX software was used to analyze the trend of constant and fluctuating forces that the mast surface suffered at different Reynolds numbers. The vortex shedding strength of the wind load around the mast was also analyzed according to the trend of Strouhal number varing with the simulated Reynolds numbers. The results show that the wind angle has an important impact on the lift, drag, and vertical forceof the mast. The vertical force of the inclined side wall on the mast can not be ignored, and the angle of direction wind has great impact on the Strouhal number at different Reynolds numbers. © (2014) Trans Tech Publications, Switzerland.
Liu X.,Harbin Engineering University |
Jin G.,Harbin Engineering University |
Wang Y.,Marine Design and Research Institute of China |
Shi Y.,Harbin Engineering University |
Feng X.,Harbin Engineering University
Journal of Computational Acoustics | Year: 2013
A numerical study on the active control of a machine suspension system supported on a cylindrical shell aiming to reduce the sound radiation is presented in this paper. In this system, a rigid-body machine is supported on a simply-supported elastic cylindrical shell through four active isolators. A theoretical model is employed and four types of active control strategies including kinetic energy minimization strategy, power flow minimization strategy, squared acceleration minimization strategy and acoustic power minimization strategy are considered, with corresponding active control force obtained by linear quadratic optimal method. Numerical simulations are conducted and detailed results were presented. Active control performance under these four control strategies is compared and analyzed in terms of radiated sound power, and the effect of the number of active actuators is discussed by numerical analysis. The results show that acoustic power minimization strategy has the best performance to reduce the sound power radiated from supporting shell in general. Through numerical simulations, some comprehensive design principles of active control system are discussed at the end. © 2013 IMACS.
Dao-ru W.,Marine Design and Research Institute of China |
Yuan-chao L.,Marine Design and Research Institute of China |
Jian-xin L.,Marine Design and Research Institute of China
Continental Shelf Research | Year: 2013
The regularities of the composition and the spatial distribution of hermatypic coral community is an essential aspect of coral reef ecosystem studies. The relationship between the structure and spatial distribution of hermatypic coral communities and hydrodynamics and wave energy, along the Changqi coast, are investigated. Differences in abundance of hermatypic coral species, at different depths, were found; these were related mainly to the varying influence of waves. Under average weather conditions, the wave energy was dissipated regularly at a depth of 2. m. Here, the coral cover was the lowest of all of the depths. However, corals growing in that area is adapted to the conditions; therefore, wave damage was low. The areas at 5-6. m water depth were influenced by waves primarily during episodes of extreme weather, with high wave energy resulting in severe damage of the corals. The coral cover in this depth was the highest observed, but the corals were generally smaller and had a short growth period. These findings indicate that the strong waves damaged particularly the weak corals, such as Acropora sp. and Montipora sp., during these short term events. Nevertheless, upon the return of normal conditions, coral communities can grow back and reproduce asexually in the damaged areas. As a result of this regrowth, Acropora sp. and Montipora sp. were highly abundant in areas at a depth of 5. m. It appears that knowledge on the physical setting, i.e. the relationship between wave properties and the spatial distribution patterns of corals, is essential for understanding coral reef succession rules; likewise, protection and recovery mechanisms of the coral reef ecosystem. © 2013 Elsevier Ltd.