Generation of random waves in time-dependent extended mild-slope equations using a source function method     

Gunwoo Kim  Changhoon Lee  Kyung-Duck Suh   《Ocean Engineering》2006,33(14-15):2047-2066

We develop techniques of numerical wave generation in the time-dependent extended mild-slope equations of Suh et al. [1997. Time-dependent equations for wave propagation on rapidly varying topography. Coastal Engineering 32, 91–117] and Lee et al. [2003. Extended mild-slope equation for random waves. Coastal Engineering 48, 277–287] for random waves using a source function method. Numerical results for both regular and irregular waves in one and two horizontal dimensions show that the wave heights and the frequency spectra are properly reproduced. The waves that pass through the wave generation region do not cause any numerical disturbances, showing usefulness of the source function method in avoiding re-reflection problems at the offshore boundary.  相似文献   

用包埋脱水法冰冻保存海洋饵料金藻   总被引：4，自引：0，他引：4  

王起华  李贺  张恩栋  高艳萍  李大鹏 《海洋与湖沼》2005,36(2):172-178

用包埋脱水法冰冻保存绿色巴夫藻(Pavlova uiridis)、湛江等鞭金藻(Isochrysis zhanjiangensis)和球等鞭金藻(Isochrysis galbana 3011)等三种海洋饵料金藻，探讨了脱水速率、胶球含水量以及化冻后恢复方法对冰冻保存存活率的影响。结果表明，三种藻都在-0．9％含水量／h的平均脱水速率下获得最高存活率：各种藻在冰冻前的胶球最佳含水量不同，绿色巴夫藻为35％，湛江等鞭金藻和球等鞭金藻都为30％。化冻后，含绿色巴夫藻的胶球在培养基中22℃暗放置48h存活率最高；另两种藻在相对湿度为75％的气相中22℃暗放置12h存活率最高。在本实验条件下，绿色巴夫藻、湛江等鞭金藻和球等鞭金藻的冰冻保存的存活率可分别达到74％、15％和17％。  相似文献   

Numerical and experimental study on hydrodynamic interaction of side-by-side moored multiple vessels   总被引：2，自引：0，他引：2  

S.Y. Hong  J.H. Kim  S.K. Cho  Y.R. Choi  Y.S. Kim 《Ocean Engineering》2005,32(7):783-801

This paper aims to investigate the basic interaction characteristics of side-by-side moored vessels both numerically and experimentally. A higher-order boundary element method (HOBEM) combined with generalized mode approach is applied to analysis of motion and drift force of side-by-side moored multiple vessels (LNG FPSO, LNGC and shuttle tankers). Model tests were carried out for the same floating bodies investigated in the numerical study in regular and irregular waves. Global and local motion responses and drift forces of three vessels are compared with those of calculations. Discussions is highlighted on applicability of numerical method to prediction of sophisticated multi-body interaction problem of which motion behavior is very important to analysis of mooring dynamics of deep sea floating bodies.  相似文献   

海带膳食纤维的提取与功能性试验   总被引：2，自引：1，他引：2  

李来好  陈培基  李刘冬  杨贤庆  吴燕燕  刁石强  薛长湖 《中国海洋大学学报(自然科学版)》2003,33(5):687-694

采用酶技术和化学处理相结合的方法 ,研究了海带膳食纤维的工艺技术 ,筛选出海带膳食纤维提取和漂白的最佳工艺条件 ,提取出海带膳食纤维产品 ,并进行人体的功能性试验。结果表明 ,海带膳食纤维的产率达 2 7.3% ,颜色为类白色 ,膳食纤维含量达 73.3% ,钙含量 7.5% ,膨胀力为55m L/ g,持水力为 2 650 % ;海带膳食纤维的功能性优于小麦麸皮膳食纤维 ,对便秘患者具有良好的疗效。  相似文献   

海水中234Th的超低水平液闪谱仪测定   总被引：2，自引：1，他引：2  

李鸿宾  黄奕普  陈敏  刘广山  邱雨生 《台湾海峡》2004,23(2):199-207

本文提出了利用超低水平液闪谱仪测定海水中234Th的方法.海水经氢氧化铁吸附共沉淀富集后,接着用阴离子交换和TBP/煤油萃取进行Th同位素的分离与纯化.对一系列测定条件进行了详细的研究,提出了测定海水中234Th的适宜程序,即在含有234Th和产额示踪剂230Th的纯化后的5mol/dm3HNO3溶液中加入TBP/煤油进行萃取,然后用0.1mol/dm3HNO3反萃取,后者是先用契伦柯夫计数法测量234Th(通过234mPa),后加入闪烁液Hisafe 3用α/β模式测量α放射体230Th.对于α和β放射体液闪谱仪的计数效率分别为100%和55.7%±2.7%.234Th的化学回收率和总探测效率分别为70%～80%和30%～45%.该法测定海水中的234Th快速、简便和高效.  相似文献   

A Forced System of Two Cylinders with Various Spacings   总被引：3，自引：0，他引：3  

邹建锋  任安禄邓见 《中国海洋工程》2004,18(3):391-402

The spectrum characteristics and wake structures for a circular cylinder oscillating in a wake are investigated by use of the currently modified virtual boundary method. A forced system of two cylinders with a small spacing ( the downstream one is made to oscillate in the transverse direction) is studied and interesting flow characteristics are observed. A vortex switch and the change of vortex modes (between 2S mode and 2P mode) are observed in the “lock-in“ region. Vortex bands are formed and lost with the increasing excitation frequency. Information concerning saddle points in the flow field is obtained for different excitation frequencies. For a forced system of two cylinders with a large spacing, the upstream cylinder sheds vortexes because there is no downstream cylinder oscillating in the wake. No distinct “lock-in“ response is found for the downstream cylinder.  相似文献   

The optimum control of thruster system for dynamically positioned vessels     

C. C. Liang  W. H. Cheng 《Ocean Engineering》2004,31(1):97-110

An offshore vessel with a dynamic positioning system (DP system) needs fast response to produce thrust to counteract the environmental forces acting on it for the purpose of maintaining its position and heading as close as possible to the working position. Therefore, quick and effective modulation of the thrust is the problem to determine the thrust and the rotation angle of the thruster devices of the ship. This paper presents an effective optimum control for a thruster system, using the sequential quadratic method to achieve economical and effective modulation of the thrust and the direction of the thruster. An optimum control study of a 2280 tons DP coring vessel with five rotary azimuth thruster marine positioning is studied in detail, which can quickly and exactly estimate the thrusts and angles of direction of all the thrusters. The results can provide a valuable thruster system for a dynamically positioned vessel.  相似文献   

A new form of generalized Boussinesq equations for varying water depth   总被引：1，自引：0，他引：1  

M. Zhao  B. Teng  L. Cheng 《Ocean Engineering》2004,31(16):597-2072

A new set of equations of motion for wave propagation in water with varying depth is derived in this study. The equations expressed by the velocity potentials and the wave surface elevations include first-order non-linearity of waves and have the same dispersion characteristic to the extended Boussinesq equations. Compared to the extended Boussinesq equations, the equations have only two unknown scalars and do not contain spatial derivatives with an order higher than 2. The wave equations are solved by a finite element method. Fourth-order predictor–corrector method is applied in the time integration and a damping layer is applied at the open boundary for absorbing the outgoing waves. The model is applied to several examples of wave propagation in variable water depth. The computational results are compared with experimental data and other numerical results available in literature. The comparison demonstrates that the new form of the equations is capable of calculating wave transformation from relative deep water to shallow water.  相似文献   

A note on estimation of the Jacobian elliptic parameter in cnoidal wave theory     

Y. -S. Cho   《Ocean Engineering》2003,30(15):1915-1922

A new and simple calculating technique for the Jacobian elliptic parameter is presented in this study. The technique is very useful in generating a train of cnoidal waves in both laboratory and numerical wave tanks. Upon specification of water depth, the wave height and either the wave period or the wavelength, the proposed technique uses the Newton–Raphson method to estimate the Jacobian elliptic parameter directly, without trial and error procedures or look-up in tables. It is shown that the technique provides equally accurate results as the ad hoc methods previously used.  相似文献   

Response of the barrier island coastal region of southwestern Nigeria to climate and non-climate forcing     

IB Danladi  M Gül  E Ateş 《African Journal of Marine Science》2020,42(1):43-51

Despite threats emanating from the influence of climate and non-climate forcing on the barrier island coastal region of southwestern Nigeria, the extent of the coastal erosion is poorly understood. We report evidence of coastal erosion and sediment accumulation in the region over a 34-year period (1973–2017), using Landsat imagery at intervals of approximately six years. Landsat image corrections and various water-extraction algorithms were used to systematically delineate coastal erosion and accumulation in the area. The region was subdivided into western and eastern subregions separated by Lagos Harbour. In the west, erosion took place during the periods 1973–1979, 1979–1984, 1990–1999 and 2005–2011, whereas in the east, erosion occurred during 1973–1979, 1990–1999 and 1999–2005. Coastal sediment accumulation occurred in the east during 1979–1984, 1984–1990, 2005–2011 and 2011–2017, whereas gains in the west occurred during 1984–1990, 1999–2005 and 2011–2017. The study revealed substantial net erosion of 1 228.1 ha in the region as a whole, over the full period. Sediment accumulation accompanying the coastal erosion appears to be linked to longshore drift. Erosion between 1973 and 2011 was probably attributable to climate change (storms and tidal conditions), longshore drift, the inflow and outflow of water at Lagos Harbour, coastal morphology and, possibly, human impacts. However, the coastal changes between 2011 and 2017 were more obviously associated with human activities, such as development of the Eko Atlantic construction project. Coastal surveillance, together with the use of environmentally sensitive protective measures, could possibly help to reduce coastal erosion in the region. Careful coastal management practices, including artificial nourishing and the installation of resilient structures (e.g. seawalls), should be undertaken to protect human settlements that are already at risk from sea-level rise.  相似文献