粒子群算法在翼型剖面优化中的应用

为设计出具有良好升阻比性能的翼型剖面,采用智能优化领域新兴的粒子群优化算法(PSO)结合面元法对翼型进行优化设计。文中给出了PSO算法的数学模型及其在翼型优化设计中的主要计算过程,并以Naca66mod翼型为原型进行设计。获取了翼型优化过程中每一步处的翼型剖面形状、翼型表面压力系数分布以及翼型的升力系数、阻力系数和最大厚度比,结果分析表明经过优化后的翼型与原型相比,具有升力系数增加,阻力系数减小这一有利的特征改变。同时采用CFD方法对两种翼型进行数值模拟计算,获得同上的结论,进而验证了PSO方法在翼型优化设计中的可行性。     

吸力式基础在深水油气田开发中的应用探讨

基于吸力式基础在全球深水油气田开发设施中的工程应用调研结果,对比分析此类基础较其他基础型式的优势,介绍吸力式基础的设计和施工过程应该着重考虑的问题,展望其在国内的应用前景。     

隔振器和垫板贴合率的测量方法研究

在机械隔振系统中,采用传统的蓝油法和塞尺法都无法较完整地反映金属隔振器与垫板间的接触状况。考虑到金属间的贴合程度主要由组件所受的压力及两接触面物理特性所决定,研究提出了一种用于检测垫板和金属隔振器贴合率的工程实用测量方法,并通过多样本试验,证实了方法的可行性。该方法操作简便,检测结果可信。     

基于局部横向强度要求的船舶侧向承载板厚度设计研究

液体的压强作用一直是船体外板、液舱舱壁等位置板厚设计的主要考虑因素之一,且可归结为局部板格在侧向载荷作用下不屈服的安全衡准问题。结合理论分析及非线性有限元数值计算,对于受侧向载荷作用的局部板格极限强度的影响,探讨了包括边界条件、大挠度问题及相应的薄膜效应等各种影响因素,论证了一种优化的受侧向载荷作用的船体板厚约束设计公式,该公式经济适用且安全。整个探讨过程为船体结构规范的进一步完善提出了建议。     

远岸深水通用码头平面布置研究

张家港宏泰通用码头前方作业平台远离后方堆场,为典型的远岸深水码头,且兼具中转功能,需要停靠数量较多、大小差别较大的船舶,综合考虑工程造价、码头功能及与临近已建工程之间的关系等因素,提出了“T”型布置方案,提高了港口岸线的利用率。     

Centrifuge modelling of pipe-soil interaction in clay with crust layer

Seabed in regions, such as the Gulf of Guinea and North West Shelf of Australia, may exhibit a crust layer where the undrained shear strength can be an order of magnitude higher than that of the immediately underlying sediment. This can complicate design of steel catenary risers, where fatigue depends on the cyclic vertical stiffness of the pipe-soil interaction. Potential punch-through of the riser into the underlying soft soil may invalidate design assumptions based on the pipe-soil stiffness within the crust layer. The long-term evolution of pipe-soil stiffness within the crust layer, which exhibits similar properties to an over-consolidated soil, is also poorly understood. This paper describes centrifuge model tests undertaken in a clay sample with a crust layer, simulating the punch-through process of a pipe under load control and investigating the pipe-soil stiffness during long-term cyclic loading tests under displacement control. Results confirm that the potential for punching-through the crust layer depends strongly on the relative ratio of pipe diameter to crust layer thickness. The long-term evolution of pipe-soil stiffness showed a steady increase after an initial remoulding stage in contractile soils (normally consolidated and lightly over-consolidated), but a steady reduction in the heavily over-consolidated, more dilatant, crust. The magnitude of pipe-soil stiffness changes (during both remoulding and reconsolidation) is governed by the over-consolidation ratio of the soil and the amplitude of the cyclic displacements. This study provides insights on the relevant cyclic stiffness to consider when assessing SCR fatigue life in over-consolidated soils and soils exhibiting a superficial crust layer.     

Fitness-for-purpose assessment of cracked offshore wind turbine monopile

In this paper, the procedure for flaw acceptability assessment is examined through a case study of a semi-elliptical surface crack in an offshore monopile as it grows till it forms a through thickness crack. Using the procedure prescribed in an industrial standard (BS 7910), the fracture ratio, K_r is shown to increase monotonically with increasing crack depth. The load ratio, L_r, is initially insensitive to the crack depth. However, there is a rapid increase in L_r when the crack depth to thickness ratio exceeds 80%. L_r values obtained from detailed 3D FE limit analysis using elastic-perfectly-plastic material behaviour do not exhibit the asymptotic behaviour predicted by BS 7910 as the flaw transitions from deep crack to through-thickness crack. Furthermore, K_r predicted by BS 7910 is shown to be an over-estimation for the typical dimensions of offshore monopiles. The findings suggest that a structure with a deep flaw may be identified as unacceptable based on BS 7910 when it may still possess a non-trivial amount of structural residual life. This is a concern for monopiles where crack growth as a large flaw forms a significant part of the total life.     

Three-dimensional vortex-induced vibrations of a circular cylinder predicted using a wake oscillator model

This paper reports a numerical study based on a wake oscillator model, to determine the three-dimensional vortex-induced vibration (VIV) responses on a flexible cylinder with pinned-pinned boundary conditions subjected to a uniform flow. Four different aspect ratios have been selected for the study. The coupling equations of the structural oscillator models and wake oscillator models in both the cross-flow (CF) and in-line (IL) directions have been solved using a standard central difference method of the second order. The structural displacement, structural frequency, response wave pattern, response trajectory, and lift force coefficient, for four aspect ratios, have been compared. The numerical results establish that, for a small aspect ratio, the CF displacements have absolute standing wave behaviors without travelling wave behaviors, and the IL displacements have dominant standing wave behaviors with slight travelling wave behaviors. Further, the VIV trajectory is repeatable and displays figure-eight shapes. However, for a large aspect ratio, the CF displacements display identical characteristics with the IL displacements for a small aspect ratio, and the IL displacements for a large aspect ratio are simultaneously dominated by standing and travelling wave behaviors. Moreover, the VIV trajectory is apparently aperiodic and shows chaotic shapes.     

法标条件下水泥砂在堆场基层中的应用

在石料缺乏地区港口建设中,堆场基层采用常规稳定类粒料,对石料需求量比较大,导致建设成本很高。为充分利用当地资源、节约投资费用,进行水泥砂应用于堆场基层的研究。基于法国标准,采用符合要求的沉积砂或经冲击作用而分解的花岗岩质砂为原材料,以CBR值作为水泥砂主要设计控制指标和强度标准,采用路拌机现场拌和施工,并通过试验段完成各项指标的检测和验证。结果表明,在资源条件受限地区可以选择水泥砂作为港口堆场的基层材料,可有效解决工程所在地石料匮乏问题。     

120#乳化重油掺水率对实船柴油机的影响

针对乳化120#重油时掺水率变化在船舶实际运行中对柴油机燃烧与节能减排的影响,利用重油智能在线乳化装置,在以G6300ZC18B型柴油机为动力的“宁大6号”运输船进行实船试验.结果表明:掺水率在16％～22％时,爆发压力、排气温度和冷却水出口温度参数虽有变化,但都处于正常工作范围,能够保证船舶正常航行;耗油量降低.掺水率在20％时节油效果较好,NOx、碳烟以及CO排放降低.燃烧乳化重油具有节约能源和减少排放的效果.