Time-Domain Analysis for 3-D Moored Systems

In the paper, a comprehensive numerical study on the moored system is performed in time domain. The moored system, which is composed of the floating body sub-system and the mooring line sub-system, is calculated as a whole system by coupling. A time-domain method is applied to the analysis of the mooring line sub-system, and at the same time, an indirect time-domain method translated from frequency-domain to time-domain is developed to calculate the floating body sub-system. In the end, an FPSO vessel is calculated as a numerical example by the present method. A comparison of the result of the model test and that of the numerical method indicates that the present method is exact and effective.     

近岸水域中污染羽流的运动及访问频率场模型

本文研究了由污水排海工程污水扩散器排放污水形成的污染羽流在近岸水域中的运动及访问频率场模型。在对Churchill羽流运动模拟法改进的基础上,提出了羽流分片模拟法。本方法利用质量守恒原理给出了其变化关系,并采用连续释放质点追踪法计算羽流的运动路径。考虑到非保守性物质的衰减,给出了相应的计算羽流宽度的公式。对大连市黑石礁污水排海工程方案A污染羽流(以大肠杆菌作为污染指标物)访问频率场的计算表明:访问频率场对于污水排海工程环境影响预测评价和最优排污点的选择具有十分重要的意义。     

海上结构物的Ringing现象

介绍近年来新发现的海上结构物在高海况下遇到的一种现象－－ｒｉｎｇｉｎｇ高频共振响应现象及这一现象现有的研究成果，包括该现象的发现过程、特征、产生的机理及研究方法等。提出了研究ｒｉｎｇｉｎｇ现象的一种可能的新方法。     

高频地波雷达反演海浪的海上对比验证方法研究

在介绍高频地波雷达反演海浪要素工作原理的基础上 ,利用 2 0 0 0年 10月在浙江舟山海域进行的 OSMAR2 0 0 0和 SZF1- 海上对比验证实验中所获取的资料进行系统比较分析 ,验证了OSMAR2 0 0 0探测海洋海浪要素的精度 ,并分析了 OSMAR2 0 0 0反演海浪时的误差成因     

海上地震系统低频响应与电缆噪音

海上勘探地震采集的数据中低频率成分常常受到外部环境噪音的严重干扰。如何有效地剔除噪音 ,拾取更多的地震数据中低频成分。本文从分析地震仪器低频响应入手 ,得出了地震系统与电缆噪音的一些内在联系 ,就如何有效地压制外围环境噪音等问题 ,提供了有效的方法 ,为野外作业提供参考     

长江口北支潮汐能源的综合利用

长江口北支有着丰富的潮汐能源及淡水，航运、水产等资源，因长期未加规划、治理，以致远未开发利用，反使河道淤浅，迳流减少，通航能力降低，且有大量泥沙，盐倒灌南支，恶化航道、水质，亟待整治、开发。研究提出，北支潮汐能可有效地用以发电和疏浚河道。可利用北支有利的河势，建造大、小双库开发方式的潮汐电站，并利用该河上、下游端间具有潮时差的有利因素，使电站可以连续不断发电、供电。同时可利用建造的上、中、下游三座水闸，逐级集水攻沙，冲刷航道淤沙，提高通航能力，实现江、海直接联运。另可兼收淡水供应，水产养殖、旅游，以及沟通崇明岛与苏北的陆上交通等效益，潮汐电站工程可采用现实可行的新技术、新材料、新的结构形式，以降低造价，使我国潮汐能得到充分开发利用。     

深水风浪相关函数的研究

本文以风浪频谱和其相关函数的关系为基础,应用积分中值定理,给出了风浪相关函数的理论模型。进而以文氏等人的理论风浪频谱为原型,通过数值积分和待定系数法,给出了以风浪频谱的零阶矩m_0、峰频率ω_0和峰度因子P为参数的深水风浪相关函数式。最后把该式与数值计算值、实测值作了对比,证明本文所提出的深水风浪相关函数式较好地反映了各种不同成长状态的实际的相关函数。     

Have applications of continuous rainfall–runoff simulation realized the vision for process‐based flood frequency analysis?

Keith Beven was amongst the first to propose and demonstrate a combination of conceptual rainfall–runoff modelling and stochastically generated rainfall data in what is known as the ‘continuous simulation’ approach for flood frequency analysis. The motivations included the potential to establish better links with physical processes and to avoid restrictive assumptions inherent in existing methods applied in design flood studies. Subsequently, attempts have been made to establish continuous simulation as a routine method for flood frequency analysis, particularly in the UK. The approach has not been adopted universally, but numerous studies have benefitted from applications of continuous simulation methods. This paper asks whether industry has yet realized the vision of the pioneering research by Beven and others. It reviews the generic methodology and illustrates applications of the original vision for a more physically realistic approach to flood frequency analysis through a set of practical case studies, highlighting why continuous simulation was useful and appropriate in each case. The case studies illustrate how continuous simulation has helped to offer users of flood frequency analysis more confidence about model results by avoiding (or exposing) bad assumptions relating to catchment heterogeneity, inappropriateness of assumptions made in (UK) industry‐standard design event flood estimation methods, and the representation of engineered or natural dynamic controls on flood flows. By implementing the vision for physically realistic analysis of flood frequency through continuous simulation, each of these examples illustrates how more relevant and improved information was provided for flood risk decision‐making than would have been possible using standard methods. They further demonstrate that integrating engineered infrastructure into flood frequency analysis and assessment of environmental change are also significant motivations for adopting the continuous simulation approach in practice. Copyright © 2016 John Wiley & Sons, Ltd.     

Direct estimation of catchment response time parameters in medium to large catchments using observed streamflow data

In single‐event deterministic design flood estimation methods, estimates of the peak discharge are based on a single and representative catchment response time parameter. In small catchments, a simplified convolution process between a single‐observed hyetograph and hydrograph is generally used to estimate time parameters such as the time to peak (T_P), time of concentration (T_C), and lag time (T_L) to reflect the “observed” catchment response time. However, such simplification is neither practical nor applicable in medium to large heterogeneous catchments, where antecedent moisture from previous rainfall events and spatially non‐uniform rainfall hyetographs can result in multi‐peaked hydrographs. In addition, the paucity of rainfall data at sub‐daily timescales further limits the reliable estimation of catchment responses using observed hyetographs and hydrographs at these catchment scales. This paper presents the development of a new and consistent approach to estimate catchment response times, expressed as the time to peak (T_Px) obtained directly from observed streamflow data. The relationships between catchment response time parameters and conceptualised triangular‐shaped hydrograph approximations and linear catchment response functions are investigated in four climatologically regions of South Africa. Flood event characteristics using primary streamflow data from 74 flow‐gauging stations were extracted and analysed to derive unique relationships between peak discharge, baseflow, direct runoff, and catchment response time in terms of T_Px. The T_Px parameters are estimated from observed streamflow data using three different methods: (a) duration of total net rise of a multipeaked hydrograph, (b) triangular‐shaped direct runoff hydrograph approximations, and (c) linear catchment response functions. The results show that for design hydrology and for the derivation of empirical equations to estimate catchment response times in ungauged catchments, the catchment T_Px should be estimated from both the use of an average catchment T_Px value computed using either Methods (a) or (b) and a linear catchment response function as used in Method (c). The use of the different methods in combination is not only practical but is also objective and has consistent results.     

Probability distribution type of Canadian annual minimum streamflow / Type de distribution de probabilité du débit minimum annuel au Canada

Abstract

The method of L-moment ratio diagrams along with the averaged weighted distance (AWD) is applied to identify a probability distribution of annual minimum streamflow, namely annual minimum daily streamflow in 11 climatic regions of Canada. Across the entire country, the Pearson type III probability distribution is an acceptable distribution for describing annual minimum streamflow with the 3-parameter lognormal and log Pearson type III distributions as potential candidates. Some minor differences in the probability distribution type among different climatic regions are also observed, which may be taken into account in the selection of the distribution type of annual minimum streamflow.