海堤前特殊地形对护面块体稳定性影响及对策

通过在波浪水槽内对海堤护面块体稳定性物理模型试验,发现在堤前存在特殊地形的条件下,波浪传播该区域后发生变形、破碎,形成的波能集中冲击范围内护脚人工块体,导致其失稳,进而使断面上整个护面块体向海侧滑移失稳。文章分析了块体失稳原因和影响因素,并从设计角度提出多种针对特殊地形下人工块体失稳的改善措施。     

波浪模型试验应当注意的一些问题

根据实践经验,按照波浪物理模型试验要求、工作大纲、试验条件、制作模型、试验过程和报告编写等环节,总结了容易疏忽的问题,并给出了解决这些问题的方法和建议,以促进模型试验成果的科学性和可靠性,提高工作效率,避免不必要地失误。可供从事此项工作人员特别是经验不多的年轻人借鉴和参考。     

高桩码头三维效应影响区域的缺陷检测分析

由于上部结构的影响,当采用低应变反射波法进行高桩码头桩基检测时,会出现不满足一维应力波基本假定的情况。利用LS—DYNA有限元软件模拟高桩码头群桩结构,发现桩顶以下10m深度范围内都会受到三维效应的严重影响,检测结果呈现出类似于浅部缺陷的特征。利用各种浅部缺陷的定位方法对该区域进行检测,得出纵波改进方法在该区域不再有效,只有结合扭转波检测等方法才能有效定位缺陷,对于实现高桩码头桩基质量的全面检测具有重要的借鉴意义。     

多阶底部上的垂直可渗透结构斜海洋波的阻尼研究(英文)

Oblique ocean wave damping by a vertical porous structure placed on a multi-step bottom topography is studied with the help of linear water wave theory. Some portion of the oblique wave, incident on the porous structure, gets reflected by the multi-step bottom and the porous structure, and the rest propagates into the water medium following the porous structure. Two cases are considered: first a solid vertical wall placed at a finite distance from the porous structure in the water medium following the porous structure and then a special case of an unbounded water medium following the porous structure. In both cases, boundary value problems are set up in three different media, the first medium being water, the second medium being the porous structure consisting of p vertical regions-one above each step and the third medium being water again. By using the matching conditions along the virtualvertical boundaries, a system of linear equations is deduced. The behavior of the reflection coefficient and the dimensionless amplitude of the transmitted progressive wave due to different relevant parameters are studied. Energy loss due to the propagation of oblique water wave through the porous structure is also carried out. The effects of various parameters, such as number of evanescent modes, porosity, friction factor, structure width, number of steps and angle of incidence, on the reflection coefficient and the dimensionless amplitude of the transmitted wave are studied graphically for both cases. Number of evanescent modes merely affects the scattering phenomenon. But higher values of porosity show relatively lower reflection than that for lower porosity. Oscillation in the reflection coefficient is observed for lower values of friction factor but it disappears with an increase in the value of friction factor. Amplitude of the transmitted progressive wave is independent of the porosity of the structure. But lower value of friction factor causes higher transmission. The investigation is then carried out for the second case, i.e., when the wall is absent. The significant difference between the two cases considered here is that the reflection due to a thin porous structure is very high when the solid wall exists as compared to the case when no wall is present. Energy loss due to different porosity, friction factor, structure width and angle of incidence is also examined. Validity of our model is ascertained by matching it with an available one.     

波导中带帽圆柱壳的声辐射快速预报(英文)

In order to predict acoustic radiation from a structure in waveguide, a method based on wave superposition is proposed, in which the free-space Green's function is used to match the strength of equivalent sources. In addition, in order to neglect the effect of sound reflection from boundaries, necessary treatment is conducted, which makes the method more efficient. Moreover, this method is combined with the sound propagation algorithms to predict the sound radiated from a cylindrical shell in waveguide. Numerical simulations show the effect of how reflections can be neglected if the distance between the structure and the boundary exceeds the maximum linear dimension of the structure. It also shows that the reflection from the bottom of the waveguide can be approximated by plane wave conditionally. The proposed method is more robust and efficient in computation, which can be used to predict the acoustic radiation in waveguide.     

航行工况下自升式风车安装船强度直接计算研究

自升自航式风车安装船为海洋工程专业特种船舶,在风机运输,安装中有很高的实际利用价值。采用直接计算法,对航行工况下自升自航式风电安装船的总强度进行评估。建立了船体和桩腿的有限元建模,基于三维势流理论对波浪垂直弯矩进行长期预报,得到风车安装船在典型装载工况下的设计波参数,将船舶在设计波中的重力、静水压力、水动压力、惯性力等施加到模型上进行直接强度分析,对航行工况下船体和桩腿的强度进行了校核。本文的计算方法及结果可为自升自航式风车安装船的整体强度评估、船体结构优化提供有效依据,并且对同类工程船的设计开发具有指导意义。     

波浪作用下开孔混凝土护面板稳定性研究

在混凝土护面板上开孔,一方面可增大与坡面的摩阻力,提高抗滑性能;另一方面增大了护面层的渗透系数,增强了面板的整体稳定性。通过不规则波系列试验,对不同开孔率混凝土护面板稳定性的影响因素进行了研究,提出了稳定厚度计算公式,并与现行规范的混凝土板和栅栏板稳定厚度公式进行了对比。该公式具有较好精度,可为工程设计提供参考依据。     

斜入射水波对直立防波堤的波浪渗流作用

基于Biot渗流固结理论和水波绕射理论,应用特征函数展开法,推导了对应直立防波堤的绕射波势和波浪引起的海床内渗流压力分布的解析式,由此计算了作用于直立防波堤底部上由波浪渗流压力所导致的浮托力和倾覆力矩,并与水平波浪力和力矩进行了相应比较。计算结果表明,在一定条件下,波浪渗流作用与水平波浪作用可以具有相同的量级。波浪入射角,防波堤前侧透空及海况条件防波堤几何尺寸等因素的相对变化对波浪渗流作用均存在一定的影响,其中对渗流倾覆力矩的影响更为明显。     

半潜式钻井平台用钢DH36安定行为试验研究

为了给半潜式钻井平台的安全性和寿命评价提供可靠试验依据,在室温下对半潜式钻井平台用钢DH36钢进行了考虑加载波形、加载速率和应力比影响的多工况单轴棘轮安定试验。结果表明:循环硬化速率随循环周次的增加快速下降,在低于某一值的循环应力作用下,应变将最终趋于棘轮饱和状态;正弦应力波比三角波更快地趋于安定,采用较低的加载速率可以加速材料趋向饱和棘轮状态;峰值应力固定不变时,棘轮应变对应力比历史无明显的记忆性;波形和加载速率对饱和棘轮应变的影响有限,饱和棘轮应变随着应力峰值的增加而增大。     

波浪作用下30万吨级油轮撞击能量研究

通过物理模型试验,研究不规则波作用下30万吨级油轮撞击能量,分析了主要影响因素HT、LB、TT0、D对撞击速度的影响规律。结果表明:撞击速度与HT成正比;与LB成幂次关系;与TT0也成正比,但TT0=1时船舶撞击码头与波浪产生共振,撞击速度出现极大值;压载时的撞击速度大于满载时的撞击速度,撞击速度与吃水成负相关。提出了30万吨级油轮撞击能量的计算公式,与青岛港原油码头三期工程和青岛益佳集团燃油码头工程的物理模型试验结果对比,具有较好的计算精度,可供工程设计参考。