在波浪荷载作用下插入式大圆筒结构稳定性分析评述

结合某大圆筒结构工程，对大圆筒结构稳定性分析中的各种计算方法进行了综合评述与讨论，尤其对大圆筒结构在波浪荷载作用下，各方法采用的受力计算模式及其计算结果进行了深入剖析，明确了一些概念性问题，有助于促进本课题的进一步发展。     

波浪作用下软基上沉入式大直径圆筒结构的变位计算模型

文章通过所建立的软粘土地基土体的循环累积变位分析模型，对大直径圆筒原型结构在波浪引起的水平向循环荷载作用下的基础稳定性进行研究，计算分析了简体随循环次数的变位状况和临界稳定状态时简体所受到的土压力分布以及临界稳定状态的判别参数c值。     

An Approach to Stability Analysis of Embedded Large-Diameter Cylinder Quay

The large-diameter cylinder structure, which is made of large successive bottomless cylinders placed on foundation bed or partly driven into soil, is a recently developed retaining structure in China. It can be used in port, coastal and off-shore works. The method for stability analysis of the large-diameter cylinder structure, especially for stability analysis of the embedded large-diameter cylinder structure, is an important issue. In this paper, an idea is presented that is, em-bedded large-diameter cylinder quays can be divided into two types, i.e. the gravity wall type and the cylinder pile wall type. A method for stability analysis of the large-diameter cylinder quay of the cylinder pile wall type is developed and a method for stability analysis of the large-diameter cylinder quay of the gravity wall type is also proposed. The effect of sig-nificant parameters on the stability of the large-diameter cylinder quay of the cylinder pile wall type is investigated through numerical calculation.     

不同间距大直径圆筒防波堤波压力试验研究

通过开展物理模型试验,进行不规则波作用下不同间距大直径圆筒防波堤的波峰压力分布规律研究,分析了圆筒相对间距、相对水深、波陡等主要影响因素对圆筒波压力的影响规律,并通过波压力试验值与各家理论公式计算值的比较,进行不同间距圆筒波压力的计算方法研究。基于直立墙结构和大尺度孤立墩柱结构波压力公式给出修正系数以及横向衰减函数的拟合公式,用以计算圆筒周身不同位置处的波压力,从而为工程设计和理论研究提供参考。     

基于多元线性回归函数的波浪荷载实验研究

在实际工程实验与研究中，根据最小二乘法估计理论，进行多元线性回归分析是一种常见的数据处理方法。大直径圆柱壳结构是近年来在港口海洋工程中出现的一种新型结构。在大直径圆柱壳结构波浪力实验的基础上，引入多元线性回归函数对作用在大直径圆柱壳结构上的波浪力及其弯矩的计算进行了分析，并尝试给出作用在该结构上的波浪荷载公式。     

Experimental Study on Local Scour Around A Large Circular Cylinder Under Irregular Waves

1 .IntroductionWiththedevelopmentofexploitationofmarineresources ,theconstructionofoffshorestructuresdevelopsrapidly ,suchasmarineoilplatforms ,deep waterbreakwaters ,marinebridges ,largehar bors,etc .Thesestructureswillchangesurroundingwaveandcurrentconditionsandleadtolocalscourofseabed ,resultinginstructuraldamage .Therefore ,localscouraroundmarinestructuresaswellastheirprotectionhasdrawnmuchattentionfromrelativeengineeringfields .Manyscholarshaveconduct edtheoreticalanalysisandexperimentals…     

Wave Uplift Forces on the Bottom of a Circular Cylinder

The analysis of the data of model tests of two large deep wharves and monographic experimental studies show that two aspects are to be improved so as to predict the wave uplift forces on the bottom of a circular cylinder. The first aspect is the uplift pressure distribution on the bottom, and the second is the correct determination of the phase for maximum horizontal wave forces. The second problem has been solved. Synthesizing the results of theoretical analysis and experiments, we suggest a diagram for the determination of the phase when the maximum horizontal wave force appears. On the basis-ef the diagram the simultaneous wave uplift forces can be obtained for the structural stability analysis.     

Calculating the Wave Force on Partially Immersed Large-Scale Horizontal Cylinders

Large-scale interceptors constitute the main structure of offshore self-driven floating marine litter collection devices,and the structural stability of such interceptors under the action of waves directly influences the overall safety of the device.When the ratio of the diameter of a horizontal cylinder in such interceptors to the incident wavelength is larger than 0.25,the wave force can be calculated by using the diffraction theory,by considering the problem as that of the interaction between the waves and a partially immersed large-scale horizontal cylinder.In this study,an analytical approach to calculate the wave force on a partially immersed large-scale horizontal cylinder was formulated by using the stepwise approximation method.Physical model tests were conducted to investigate the effects of different factors(wave height,period,and immersion depth)on the wave force on a large-scale horizontal cylinder under conditions involving short-period waves.The results show that both horizontal and vertical wave forces on the cylinder increase as the wave height(immersion depth)increases in most cases.The vertical wave force decreases with the decrease of the period.For the horizontal wave force,it increases with the decrease of the period when the wavelength is larger than the diameter of the cylinder and decreases with the decrease of the period when the wavelength is smaller than the diameter of the cylinder.     

Numerical Investigation of Run-ups on Cylinder in Steep Regular Wave

The run-up on offshore structures induced by the steep regular wave is a highly nonlinear flow with a free surface.This article focuses on the investigation of the steep regular wave run-up on a single vertical cylinder by solving the Navier-Stokes equations. A numerical wave tank is established based on the open-source package to simulate the wave scattering induced by a vertical cylinder. The VOF method is applied to capture the large deformation and breaking of the free surface. The numerical model is validated by experimental results. The relative wave run-ups on the front face and the back face along the centerline of a cylinder are analyzed. The changes of the relative run-ups with the wave steepness, the relative diameter and the relative depth are studied. It is found that the relative run-ups on the front face and the back face of the cylinder depend mainly on the wave steepness and the relative diameter,while the dependence on the relative depth is weak. The empirical formulae are proposed to calculate the relative run-ups in terms of the wave steepness of incident regular waves and the relative diameter of a cylinder.     

波浪作用下孤立砂球稳定性条件研究

波浪作用下大块石稳定性条件的研究,不仅是泥沙运动力学急待发展的内容之一,也是抛石工程合理化设计的重要问题。在收集大量国内外有关研究资料的基础上,分析了在波浪作用下大块石的受力状况,得出当大块石处于失稳临界状态时,其所受失稳应力与其自身有效容重和其当量直径乘积的比值是雷诺数、斯特鲁哈尔数及块石水下休止角的函数。为排除块石形状和块石间相互支撑形式不规则等干扰因素的影响,采用固定钢圈支撑孤立水泥砂球,在波浪槽中进行试验研究。根据试验资料,在斯特鲁哈尔数大于10的条件下,验证了当沙粒雷诺数达到105以后Shields曲线出现跳跃的事实。     

基于预应力钢丝缠绕技术的深海超高压试验装置研制与应用

深海超高压环境模拟试验装置是深海关键技术与装备研究中必不可少的测试装置。采用传统的一体式压力筒研制大直径、超高压试验装置时难以克服应力集中的问题,安全性较低且造价昂贵。采用预应力钢丝缠绕技术研制的深海超高压环境模拟试验装置克服了其局限性,该装置是目前国内工作压力最高、可实现筒内环境数据监测且升降压自动控制的压力试验装置。文中简要介绍了该装置的系统组成及研制过程中主要关键技术问题及解决方法,最后介绍了典型实验应用,为深海超高压环境模拟试验装置的研制与应用提供参考。     

波浪作用下沙质海床上大直径圆筒结构动态响应的实验研究

通过物理模型实验,对沙质海床上沉入式大直径圆筒结构对波浪的动态响应进行了较系统的实验研究。实验中考虑了大直径圆筒、波浪和海床三者之间的耦合作用,并实时记录了大直径圆筒结构的动态响应。实验数据分析表明,大直径圆筒在波浪作用下的动态响应以大圆筒随波浪的前后摆动为主,其摆动轴心并不是固定不变的。最后通过回归分析给出了估算大直径圆筒摆动转角幅值的经验公式。     

Simulation and Analysis of a Gravity Cyh''''nder''''s Stability in Short-Crested Sea

Generally, the reliability of ami -sliding and anti-overturning stability of an isolated gravity cylinder in a certain working period can be evaluated only when the statistical properties of short term stability are given first. The authors used numerical method to simulate the stability state function of a cylinder in short-crested sea, and further to get the probabilitical characteristics of the structure's stability by time domain analysis. The external loads appeared in the state functions include horizontal wave force, lift force and the respective moments, and the loads are correlated by co- spectrum. The numerical method presented in this paper can be used not only to solve short term reliability problem directly, but to calculate and analyse the long term reliability problem as well. For circular cylinders, an example of simulation and analysis is displayed in this paper.     

Forces on partly buried, tandem twin cylinders in waves at low Keulegan-Carpenter numbers

This study deals with the forces on the circular cylinder, laid on, or partly buried in the bed with a parallel twin dummy cylinder nearby and without it. They were determined by measuring the pressure distribution on the cylinder in the case of wave at low KC numbers. The forces on the cylinder were calculated by the integration of the measured pressures determined by pressure transducers on the surface of the cylinder. Force coefficients were obtained for the low KC numbers (KC<5), for the burial-depth-to-the diameter ratio = 0-0.7. The distance between axis of the measurement and dummy cylinders to diameter ratio (x/D) was 2, 1.5 and 1. The dummy cylinder was replaced downstream and upstream of the measurement cylinder.     

卷积神经网络识别侧扫声呐影像的研究

卷积神经网络是当前应用最广泛的图像识别算法,利用大量数据对网络进行训练,即可达到快速、高效地对图像进行识别的目的 .由于卷积神经网络结构众多,且同一数据在不同网络表现也不尽相同,为了选择适用于分析沉船声呐数据的网络,使用Python搭建LeNet 5、AlexNet、VGG、GoogLeNet、ResNet系列(Res...     

Nonlinear wave interaction with a vertical circular cylinder. Part II: Wave run-up

Theoretical results for second-order wave run-up around a large diameter vertical circular cylinder are compared to results of 22 laboratory experiments conducted in regular nonlinear waves. In general, the second-order theory explains a significant portion of the nonlinear wave run-up distribution measured at all angles around the cylinder. At the front of the cylinder, for example, measured maximum run-up exceeds linear theory by 44% on average but exceeds the nonlinear theory by only 11% on average. In some cases, both measured run-up and the second-order theory exceed the linear prediction by more than 50%. Similar results are found at the rear of the cylinder where the second-order theory predicts a large increase in wave amplitude for cases where the linear diffraction theory predicts little or no increase. Overall, the nonlinear diffraction theory is found to be valid for the same relative depth and wave steepness conditions applicable to Stokes second-order plane-wave theory. In the last section of the paper, design curves are presented for estimating the maximum second-order wave run-up for a wide range of conditions in terms of the relative depth, relative cylinder size, and wave steepness.     

软粘土中插入式大直径薄壁圆筒结构的一种极限状态分析模型

根据插入式大直径薄壁圆筒结构的工作特点建立了其合理的破坏机制，以此为基础建立了受横向荷载作用的插入式大直径薄壁圆筒结构的上限法极限分析模型，从中可以得到作用于插入式大直径薄壁圆筒结构上的横向极限荷载近似的上限解；并根据上限法模型计算结果，提出了计算受横向荷载作用的插入式大圆筒结构侧壁极限抗力的简化修正模型，利用此修正模型，基于极限平衡法，可以求解作用于插入式大直径薄壁圆筒结构上的横向极限荷载。     

大直径圆筒振动下沉动力分析方法研究

本文运用纵向强迫振动多自由度结构和土体等代流变模型 ,对大直径圆筒振动下沉过程进行模拟计算 ,确定在振动锤作用下大直径圆筒的动力响应、筒壁峰值应力和可沉入性 ,并通过工程试验结果验证模拟计算方法的适用性 ,为施工控制提供依据。     

分离盘控制圆柱涡激振动的数值模拟研究

圆柱涡激振动问题一直以来备受关注,分离盘作为涡激振动抑制装置得到广泛研究。分离盘长度L与圆柱直径D之比L/D是影响抑制效果的主要因素。运用有限体积法结合RANS方程与一定的湍流模式离散和求解流场,通过编写自定义程序,使用动网格模拟结构物的运动带来的流域边界的变化,针对弹性支撑的圆柱及附加长度为0.5 D的分离盘模型,在约化速度Ur为2.5~13的情况下,对涡激振动及其抑制进行研究。结果表明:分离盘可以抑制甚至消除圆柱涡激振动,99%以上的振幅被抑制;锁定区始点被推后,锁定区变窄;附加分离盘的圆柱阻力和升力被抑制;其斯特鲁哈数(St)稍高于单圆柱St但差别不大。     

3种海产经济鱼类成熟卵膜形态的比较研究

通过扫描电镜对黑鲷,牙鲆和红鳍东方豚成熟卵膜进行比较研究,认为其卵径大小,壳膜厚薄,微型孔小管长短,孔径大小,分布密度,卵膜孔和卵孔管等形态都存在着种的差异,尤其是由漏斗状壁的前庭和漏斗底的卵孔管两个主要部分组成的卵膜孔也体现了种的特异性。黑鲷是深凹陷,短孔道型,牙鲆是浅凹陷,短孔道型,红鳍东方豚是无漏斗状凹陷,仅有一长孔道型的卵孔管和簇拥其周围众多乳突等的特殊结构,这３种鱼的卵孔管内壁肯螺纹,属