Nonlinear Static Finite Element Stress Analysis of Pipe-in-Pipe Risers

Owing to the complexity of the pipe-in-pipe (PIP) riser system in structure, load and restraint, many problems arise in the structural analysis of the system. This paper presents a new method for nonlinear static finite element stress analysis of the PIP riser system. The finite element (FE) model of the PIP riser system is built via software AutoPIPE 6.1. According to the specialties of a variety of components in the PIP riser system, different elements are used so as to model the system accurately. Allowing for the complication in modeling the effects of seabed restraint, a technique based on the bilinear spring concept is developed to calculate the soil properties. Then, based on a pipeline project, the entire procedure of stress analysis is discussed in detail, including creation of an FE model, processing of input data and analysis of results. A wide range of loading schemes is investigated to ascertain that the stresses remain within the acceptable range of the pipe material strength. Finally, the effects of the location of flanges, the thermal expansion of submarine pipelines and the seabed restraint on stress distribution in the riser and expansion loop are studied, which are valuable for pipeline designers.     

Effect of the Twin Jetties as A Regulating Structure at the Tao-er Estuary

The phase one project of the twin jetties at the Tao-er Estuary yields no effect on the flow, and there is a large area of deposition. A numerical model is employed to simulate the flow field, and the scouring and silting in the channel be-tween the two jetties are analyzed. The results show that the effective tidal flux between the two jetties is reduced due to the notch located at the heel of the east jetty, and the effect of contraction-flush is not obvious. As for the regulation of this kind of estuary under the tide action, the capability of tidal flux should be fully used.     

1998年春夏南海温盐结构及其变化特征

利用1998年5～8月“南海季风试验”期间“科学1”号和“实验3”号科学考察船两个航次CTD资料,分析了1998年南海夏季风暴发前后南海主要断面的温盐结构及其变化特征.观测发现,南海腹地基本被典型的南海水团所控制,但在南海东北部尤其是吕宋海峡附近,表层和次表层水明显受到西太平洋水的影响.季风暴发以后,南海北部表面温度有显著升高,升幅由西向东递减,而南海中部和南部表面温度基本没变,这使得南海北部东西向温度梯度和整个海盆南北向温度梯度均减小.北部断面表层盐度普遍由34以上降低到34以下,混合层均有所发展,是季风暴发后降水和风力加剧的结果.观测期间黑潮水跨越吕宋海峡的迹象明显但变化剧烈.4～5月,黑潮次表层水除在吕宋海峡中北部出现外,在吕宋岛以西亦有发现,表明有部分黑潮水从吕宋海峡南端沿岸向西进而向南进入南海.6～7月,次表层高盐核在吕宋海峡中北部有极大发展,但在吕宋岛以西却明显萎缩;虽然看上去黑潮水以更强的流速进、出南海,但对南海腹地动力热力结构的影响未必更大.一个超过34.55的表层高盐水体于巴拉望附近被发现,似与通过巴拉望两侧水道入侵南海的西太平洋水有关.     

Numerical Simulation of Non-Linear Wave Propagation in Waters of Mildly Varying Topography with Complicated Boundary

In this paper, the characteristics of different forms of mild slope equations for non-linear wave are analyzed, and new non-linear theoretic models for wave propagation are presented, with non-linear terms added to the mild slope equations for non-stationary linear waves and dissipative effects considered. Numerical simulation models are developed of non-linear wave propagation for waters of mildly varying topography with complicated boundary, and the effects are studied of different non-linear corrections on calculation results of extended mild slope equations. Systematical numerical simulation tests show that the present models can effectively reflect non-linear effects.     

大型渠系联合运行状态空间模型不确定性的描述与度量

多渠段联合的自动化运行是现代节水农业的重要发展趋势之一,也是现阶段南水北调中线运行控制的关键技术问题,其控制器的设计求解依赖于线性化的系统数学模型,而多渠段系统本身是高度非线性耦合系统。针对所建立的多渠段多输入多输出(MIMO)模型,对其不确定性的来源做分类分析,作为系统鲁棒控制器设计的基础。将线性化的模型作为标称模型,不确定性采用模型之间差异矩阵的最大奇异值表示。以一个六渠段串联的算例进行求解,得出其模型不确定性的定量描述。     

利用p~3软件进行GPS单点定位解算的若干问题

利用p3软件对大量实测数据进行了高精度单点定位有关问题的验证和分析;在IGS提供的精密星历和卫星钟差产品中,较为深入地比较分析了快速产品和几种最终产品的定位精度、收敛速度及p3软件的正反算结果精度。得出以下结论:快速产品与最终产品的定位精度和收敛速度相似;COD的收敛速度和定位精度最高;p3软件的反算精度明显优于正算,且精度也比较均匀。这些研究成果对PPP技术的实际应用具有较好的借鉴意义。     

Algorithm for Harmonic Tidal Analysis along T/P Tracks： Taking Differences of Observed Sea Surface Heights at Adjacent Points as Observations

An algorithm （differential mode） is presented for the improvement of harmonic tidal analysis along T/P tracks, in which the differences between the observed sea surface heights at adjacent points are taken as observations. Also, the observation equations are constrained with the results of the crossover analysis; the parameter estimations are performed at 0.1° latitude intervals by the least squares. Cycle 10 to 330 T/P altimeter data covering the China Sea and the Northwest Pacific Ocean （2°-50° N,105°-150° E） are adopted for a refined along-track harmonic tidal analysis, and harmonic constants of 12 constituents in 8 474 points are obtained, which indicates that the algorithm can efficiently remove non-tidal effects in the altimeter observations, and improve the precision of tide parameters. Moreover, parameters along altimetry tracks represent a smoother distribution than those obtained by traditional algorithms. The root mean squares of the fitting errors between the tidal height model and the observations reduce from 11 cm to 1.3 cm.     

鄂尔多斯坳陷湖盆缓坡型三角洲前缘沉积微相分带及成因分析——以定边-安边地区延长组长6油组为例

运用沉积相分析理论对鄂尔多斯盆地定边-安边地区晚三叠世延长组坳陷湖盆缓坡型三角洲前缘沉积微相组合进行系统研究,共识别出其组合形式有:水下分流河道叠加组合、河口坝叠加组合、水下分流河道与河口坝叠加组合以及河口坝与远砂坝、席状砂的叠加组合等4大类9种类型。并深入研究三角洲前缘沉积微相组合的时空分布规律,以三角洲前缘坡折带为界,将三角洲前缘分为"台型前缘"、"坡型前缘"和"盆型前缘"三部分,各部分有独特的沉积微相组合形式。高分辨率层序地层学的基准面旋回原理和沉积物体积分配原理表明:短期基准面的规律性变化影响着储层砂体的成因类型、叠加组合形式和空间分布规律,据此建立坳陷湖盆三角洲前缘不同沉积微相组合的成因分布模式。     

基于物方影像匹配的DEM聚类变化检测

提出了DEM的变化检测问题,采用了基于密度的聚类分析方法对匹配所得的初始变化区域进行分析,实现了地表高程变化区域的检测.