基于YOLO算法的海洋中尺度涡三维结构构建

海洋中尺度涡是一种常见的中尺度海洋现象,研究海洋中尺度涡的分布及运动特性对航运、气候、军事等具有重要作用,海洋中尺度涡的识别是海洋学和计算机科学领域的一个热门研究课题。运用深度学习的方法和框架,对中尺度涡的二维识别和三维结构构建展开研究分析。首先,获取全球海洋再分析数据并进行流线可视化,构建涡旋流线数据集;其次,利用YOLO v5s卷积神经网络对涡旋流线数据集进行训练,并对南海区域中尺度涡进行有效检测。实验结果表明,YOLO v5s训练后得到最优模型经过测试,平均检测精度均值达到了86.10%;最后,根据涡旋检测结果,对检测出的同时刻不同深度的涡旋判断是否属于同一涡旋,确定后进行该涡旋的三维结构构建。     

空间变化的涡粘系数对线性Munk边界层解的影响(英文)

基于Ｐｅｄｌｏｓｋｙ（１９８７）的线性Ｍｕｃｋ边界层模型,引入一随纬向空间变化的侧摩擦系数ＡＨ（ｘ）,以探讨该参数对西边界流的强化结构的影响。结果发现,在风应力和内区解保持不变的情况下,适中线性变化的ＡＨ（ｘ）会使西边界层内的向北急流和其靠内区一侧的逆流均得到加强。文中还给出摩擦应力、相对涡度及平均动能向涡动能的转化率在西边界层内的分布情况。     

黑潮延伸体邻近海区中尺度涡三维合成结构分析

文章基于卫星高度计资料和Argo浮标资料,采用合成方法,构建了黑潮延伸体邻近海区中尺度涡的温盐三维结构。合成结果表明,表层至1×107 Pa,合成气旋涡（反气旋涡）呈现较为一致的位温负（正）异常,气旋（反气旋）涡内呈现较为一致的位温负（正）异常,混合层至约7×106 Pa深度,气旋（反气旋）涡存在位温负（正）异常的冷核（暖）核结构。气旋（反气旋）涡的平均盐度在垂向上呈现“负—正”（“正—负”）上下相反的异常结构。     

基于拉格朗日分析法的中尺度涡精细三维结构研究及其误差估计

在前人的工作中,拉格朗日分析法被用来演示大尺度环流,同时拉格朗日拟序结构可以较好的演示中尺度涡两维结构的发展过程。然而,很少研究关注怎么利用拉格朗日分析法针对中尺度涡三维结构进行演示。与以往利用欧拉方法研究中尺度涡三维结构的工作不同,我们利用拉格朗日分析法,从另一个视角来研究涡旋结构。我们在海山上方模拟出一个理想的气旋涡,涡旋内的下沉流和涡旋旁的上升流形成一个闭合的环流。这种结构很难从欧拉角度来演示。然而,粒子的运动轨迹很好地展示了整个循环:流体在涡旋中旋转下沉,汇聚到底层的上升流区,并通过上升流返回到海表面。我们也将拉格朗日分析法应用于真实的模拟结果中。作为中国南海的一个重要现象,靠近越南中部的海域中的偶极子（反气旋涡/气旋涡）,关于其结构的研究已经比较成熟了,但这些研究主要关注的是海面过程。通过拉格朗日分析,我们很好的演示了偶极子的三维结构:流体在反气旋涡(气旋涡)内部旋转上升(下沉)。更重要的是,粒子的轨迹表明,这两个涡旋之间不存在水团交换,因为强边界急流将它们彼此分开。以上结论均得到了计算误差估计的可信度支持。尽管在强辐散流和强垂直扩散流中,计算误差逐渐增大,但是在一定的时间步长和积分周期内,计算误差始终保持在一个较小的值。     

吕宋暖涡的三维观测特征及其数值模拟分析

基于2011年春季南海北部CTD观测数据,结合高度计资料和高分辨率ROMS(Regional Ocean Modeling System,ROMS)模式对1993-2003年的模拟结果,研究了吕宋暖涡(Luzon Warm Eddy)的空间结构和生成规律。结果表明:观测中吕宋岛西北海域存在一对冷暖涡旋,其中暖涡信号是一次典型的吕宋暖涡事件,水团中携带了部分的黑潮水;该吕宋暖涡对温盐、流场结构的影响能够达到中层以下,在垂向上呈现出西北向倾斜的特征,自表层至1000 m深度范围,倾斜距离超过70 km。受到5月来自黑潮区的高水位信号影响,吕宋暖涡生成于吕宋西北局地并逐渐发展增强,持续时间达30天以上,之后向西移动,同时其后缘常伴随生成一个冷涡。在10年的数值结果中,吕宋暖涡的生成、演变过程,及其三维结构的西北向倾斜特征均与观测较为一致,模式初步证明了吕宋暖涡的演变过程是一种季节性现象。     

不同节点布置下二维涡激振动的无单元法参数化分析

尝试建立1种基于无单元法的涡激振动数值模拟算法,并给出适用于涡激振动分析的前处理自动布点方法.基于无单元法理论,使用动最小二乘法构造形函数,利用无单元伽辽金法,采用速度和压力分离模式,及手工布点和自动布点2种方法所得出的节点布置形式,对流场控制方程进行空间离散,模拟二维涡激振动的流场形态,并对VIV相关参数进行分析,计算不同节点布置情况下的升力系数(Cl)、曳力系数(Cd)及斯特罗哈数(St),并与物理模型实验结果进行对比.计算结果表明,无单元伽辽金法应用于立管VIV分析是可行的,且文中采用2种布点方法均能较好的模拟流场中泻涡脱落的形态,计算结果与传统方法和物理模型实验结果吻合良好.证明文中2种布点方法都能用于固定圆柱的二维VIV分析,但自动布点法能够更好地适用于复杂问题的计算及圆柱体在流场中的VIV动力响应分析.     

内流对海底管线涡致振动与疲劳寿命的影响

在复杂的海洋环境条件下，管道的动力学特性受到内外部流体的作用而呈现出新的特点。本文通过对处在海底平稳流动作用下的悬跨管道的涡致振动进行分析，特别地考虑到管道内部流动的作用，给出了内流速度对管道响应幅度的影响，进而指出其对管道疲劳的意义。     

“二元”基坑中内支撑支护结构的三维数值分析与监测

排桩与内支撑相结合的基坑支护结构是近几年兴起并迅速发展的1种支护方式。如何通过有效控制其变形使基坑工程安全又经济,是人们不断探索的课题。本文以青岛地区某实际深基坑为研究对象,运用理正深基坑三维协同计算对基坑开挖、支护进行了整体计算。对内支撑的平面布置进行分析,提出了水平桁架式、大直径环撑辐射式、多跨压杆式不同的支撑样式对基坑的整体受力及变形的影响参考值。对本工程内支撑的支撑间距进行分析,提出了合理的支撑间距值。另外,依据有关规定制定了监测方案,对监测结果进行了整理,并与理论计算值进行比对分析,得出一些有价值的结论,可以为类似工程的设计、施工和监测提供一些借鉴。     

开孔墙对减小波浪载荷效果的CFD分析

极限波浪载荷是导致海上结构物疲劳失效的主要载荷之一。固定在海洋基础结构物上的直立开孔墙对减小波浪载荷具有一定的效果。基于不可压缩黏性流体流动理论和N-S方程,采用VOF与Level-set相结合追踪自由表面的方法,首先建立数值波浪水槽,然后对开孔墙本身的开孔率和开孔墙与直立墙之间的相对距离,在降低反射系数和波浪力两个方面进行分析。研究结果表明,开孔墙可以明显降低作用在结构物上的波浪力,开孔墙本身的开孔率和与直立墙的相对距离会对其产生明显影响;不同波浪参数下会存在一个最佳的开孔率,但是不同波浪参数时最佳开孔率会略有不同;当开孔墙和直立墙的相对距离在0.2到0.3之间时,开孔墙的消波减载效果最佳。研究结果可为海洋工程相关设计提供一定的参考。     

Numerical simulation of fluid–structure interaction using a combined volume of fluid and immersed boundary method

In this work, a combined immersed boundary (IB) and volume of fluid (VOF) methodology is developed to simulate the interactions of free-surface waves and submerged solid bodies. The IB method is used to account for the no-slip boundary condition at solid interfaces and the VOF method, utilizing a piecewise linear interface calculation, is employed to track free surfaces. The combined model is applied in several case studies, including the propagation of small-amplitude progressive waves over a submerged trapezoidal dike, a solitary wave traveling over a submerged rectangular object, and wave generation induced by a moving bed. Numerical results depicting the free-surface evolutions and velocity fields are in good agreement with either experimental data or numerical results obtained by other researchers. In addition, the simplification of the initial free-surface deformation used in most tsunami earthquake source study is justified by the present model application. The methodology presented in the paper serves as a good tool for solving many practical problems involving free surfaces and complex boundaries.     

一种波浪能实验装置水动力学分析与优化设计

将造波水槽内二维浮体牵引弹簧回复液压缸的受力系统简化为弹簧—质量—阻尼器系统,建立数学模型,并根据牛顿第二定律得到运动方程式。采用基于简单格林函数的边界元方法对所研究浮体的水动力学系数和波浪力进行计算,对于施加给液压系统的不同外部阻尼值,由运动方程可得到相应的浮体垂荡运动位移。为求浮体对液压系统做功的最大值,在给定条件下着重对外部阻尼系数进行了优化。     

Fully nonlinear 3D interaction of bubble dynamics and a submerged or floating structure

This paper is concerned with the interaction of bubbles, a submerged or floating structure, and free surface waves. A three-dimensional fully nonlinear model has been developed based on the coupling of the boundary integral method (BIM) for bubble dynamics and free surface waves and the finite element method for structure deformation. The present method is well validated by comparing the numerical results with the experimental data. Three structure characteristics, including fixed, rigidly moving and flexible, are investigated separately to determine their influence on bubble dynamics. For a free-floating structure, the free surface causes not only a larger reduction in peak pressure for a rigid structure compared with a fixed body but also the modification of the bubble period and structural response. The interaction between a bubble and a flexible structure, in the absence of a free surface, is simulated. Both the rigid motion and the deformation at the local structure appear in the simulation. The effect of the structural thickness on the reduction in peak pressure is also considered.     

On the radiation and diffraction of water waves by a rectangular structure with a sidewall

A radiation and diffraction boundary value problem is investigated. It arises from the interaction of linear water waves with a freely floating rectangular structure in a semi-infinite fluid domain of finite water depth with the leeward boundary being a vertical wall. Analytical expressions for the radiated potentials and the diffracted potential are obtained by use of the method of separation of variables and the eigenfunction expansion method. The added masses and damping coefficients for the structure heaving, swaying and rolling in calm water are obtained by use of the corresponding radiated potentials and the wave excitation forces are calculated by use of the diffracted potential. To verify the correctness of the method, a boundary element method is used. A comparison of the analytical results with those obtained by the boundary element method is made and good agreement is achieved, which shows that the analytical expressions for the radiated and diffracted potentials are correct. By use of the present analytical solution, the added mass, damping coefficients, wave excitation force, together with the hydrodynamic effects of the draft, width of the structure and the clearance between the structure and the sidewall are also investigated.     

Hybrid three-dimensional finite-difference and finite-element analysis of seismic wave induced fluid–structure interaction of a vertical cylinder

The two-dimensional finite-difference scheme has been extended to three dimensions to solve nonlinear hydrodynamic pressures and structural responses of a deformable, vertical and circular surface-piercing offshore cylinder during earthquakes. A complete three-dimensional analysis has been made with both the three-dimensional equations of motion and the simultaneous action of three components of ground acceleration included in the analysis. Not only the magnitude but also the direction of the acting ground motion can be varied with time. The dynamic response of a cylinder is approximated by the displacements in the fundamental modes of vibration. A comparison of the dynamic displacement of the cylinder with and without surrounding sea water has been made. The flexibility of the offshore cylinder can significantly increase the hydrodynamic pressures acting on cylinder faces, that is, the fluid-structure interaction is necessary in offshore cylinder analysis. Although the hydrodynamic pressure induced by the vertical ground acceleration of the El Centro 1979 earthquake is significant, the calculated structural dynamic response of a cylinder is very small and the corresponding resultant hydrodynamic force is almost nil. The hydrodynamic force induced by two-horizontal ground acceleration is about the same as that by three simultaneous components of ground acceleration. For a solid and stubbier circular cylinder, the vertical component of ground acceleration may be neglected.     

海底宏渗漏气体走航式海洋电阻率法探测效果模拟与观测系统设计

为实现海底宏渗漏气体连续调查,提出了一种走航式海洋电阻率探测技术。根据前人原位观测资料和含气水体电阻率特征构建地电模型;采用数值模拟和室内试验方法获得不同参数电阻率映像剖面,分析确定探测剖面异常特征,评价探测效果。在此基础上进一步进行了探测系统设计和实验测试。研究结果表明,走航式海洋电法探测电缆可由2个供电电流极和8个电位测量极组成,电位极距需小于0.05 m;测量可采用偶极装置通过并行采集方式实现。气体分布区表现为高阻异常,异常模式由走航速度、排列长度和气体分布区横向宽度共同决定,可分为7种情形;探测电阻率极大值和气体喷出流速存在正相关指数关系。该技术可实现气体分布范围和喷出速率快速探测。     

The effect of a natural water-movement related disturbance on the structure of meiofauna and macrofauna communities in the intertidal sand flat of Rocas Atoll (NE, Brazil)

Rocas, the only atoll in the South Atlantic, is located 266 km off the northeast Brazilian coast. Spatial patterns in community structure of meiofauna, particularly nematodes, and macrofauna were examined along a transect through the sediment path from windward to leeward of the Rocas Atoll sand flat. Differences in benthic community structure between four zones of the sand flat were found to be significant and related to the major local processes of carbonate-grain transport and sedimentation. Both meiobenthic and macrobenthic assemblages were significantly more diverse and abundant within the sediment inflow zone (the initial part of the detrital path of Rocas sand flat) than in the other zones, where a clear impoverishment of benthic invertebrates occurred. This first study of the benthos of an intertidal sand flat over a reef island in the Atlantic showed that the meiofauna is numerically dominated by the nematodes Metoncholainussp. 1 (Oncholaimidae) and Epsilonema sp. 1 (Epsilonematidade), whilst the macrofauna is largely dominated by oligochaetes and large Oncholaimidae nematodes. Analysis of the species composition, trophic structure and abundance of both the meiobenthos and the macrobenthos revealed an impoverished community subjected to an intense water-movement disturbance.