Field Test and Numerical Simulation of Tidal Bore Pressures on Sheet-Pile Groin in Qiantang River

A field test of bore pressures on a sheet-pile groin in the Qiantang River was carried out to investigate the characteristics of tidal bore pressures in which temporal and spatial distributions of bore pressures on the sheet-pile groin were obtained through the test. The standard turbulence model was used to simulate the propagation of the tidal bore over a sheet-pile groin with the free surface tracked by the volume of fluid (VOF) method. With the simulated bore pressure over the sheet-pile groin, a finite difference method was used to simulate the dynamic response of the sheet-pile groin subjected to bore pressures. Good agreement between the field test and the simulated results validated the present numerical method. It was found that the bore pressures on the sheet-pile groin varied linearly in the vertical direction and obtained maximum value at the still water level. Bore pressures below the still water level decreased slightly with the depth and were characterized by a trapezoidal distribution.     

涌潮冲击丁坝的数值计算

鉴于钱塘江涌潮水流复杂多变和带有自由表面的情况,采用VOF方法追踪自由表面,考虑各向异性,用修正的K吨模型封闭Reynolds方程,用施主一受主法求解流体体积函数控制方程,计算了涌潮冲击丁坝时的压力场和自由面状况,并与现场实测值进行了比较,取得了良好的效果,为涌潮的小尺度数值模拟提供了借鉴的经验。     

水平轴潮流能水轮机数值模拟方法对比分析

叶素动量理论和CFD方法是水平轴潮流能水轮机性能分析中运用较为广泛的数值模拟方法,文中结合小尺寸水轮机模型试验,对比分析了叶素动量理论和CFD方法在水轮机性能分析中的准确性和适用性.验证结果表明:叶素动量理论和CFD方法均能对水轮机的性能进行预报,且CFD精度高于动量叶素理论;大尖速比时,动量叶素理论偏离较高,不再适合性能预报;在小尖速比下,建议采用RNGk-ε模型的CFD方法进行分析计算;动量叶素理论适合设计初期设计方案的对比分析,而CFD方法适合对设计结果的验证校核和详细分析.     

楔形体在波浪中自由入水的数值模拟

物体入水时波浪的影响不可忽略,基于流体力学模型采用VOF法,并利用自定义函数,模拟了楔形体的自由入水过程;同时结合推波板原理及海绵层消波理论实现了数值水槽的造消波,完成了波浪中楔形体自由入水的模拟,计算了楔形体入水时所受的水作用力、自由液面变化及物面压强分布等,研究了不同波高、周期以及在波浪不同位置入水时对楔形体的影响。结果表明:本文建立的数值模型可很好地模拟楔形体入水造成的射流及空泡的形成发展过程,波浪对楔形体入水的影响主要由波浪内部流场变化及表面波形决定,在波浪不同位置处入水对楔形体受力及入水形态均有较大影响。     

Numerical Analysis of Hydrodynamic Pressure Induced by Fluid-Solid Impact

—As a further development of the authors'work(Huang and Qian,1993),in this paper a newnumerical method based on the time domain boundary element technique is proposed for solving fluid-sol-id coupling problems,in which a rigid body impacts normally on the calm surface of a half-space fluid.Afundamental solution to the half-space potential flow problem is first derived with the method of images.Then,an equivalent boundary integral equation in the Laplace transform domain is established by meansof Green's second identity.Through the inverse Laplace transform and discretization in both time andboundary of the fluid region,the numerical calculation for the problem under consideration has been car-ried out.Several examples demonstrate that the present method is more efficient than existing ones,fromwhich it is also seen that the shape of the impacting body has a considerable effect on the total impactforce.     

Numerical Analysis of Factors Influencing Implosion

-By using gas-liquid two-phase flow theory, a modified mathematical model based on the computational fluid dynamics method SIMPLE (Semi-Implicit Method for Pressure-Linked Equations) is introduced to investigate implosion phenomena in high pressure chambers systematically. A theoretical simulation-prediction method, which is independent of experimental data, is developed in the paper and great improvement has been made on the topic. In the paper, various implosion situations have been simulated and predicted. Effects of a series of factors influencing implosion results and methods of reducing implosion danger have been analysed. The analysis results are of importance to underwater engineering practice.     

Numerical Analysis on the Effects of Submerged Depth of the Grid and Direction of Incident Wave on Gravity Cage

In this paper,the numerical model of the net cage with the grid mooring system in waves is set up by the lumped mass method and rigid kinematics theory,and then the motion equations of floating system,net system,mooring system,and floaters are solved by the Runge-Kutta fifth-order method.For the verification of the numerical model,a series of physical model tests have been carried out.According to the comparisons between the simulated and experimental results,it can be found that the simulated and experimental results agree well in each condition.Then,the effects of submerged depth of grid and direction of incident wave propagation on hydrodynamic behaviors of the net cage are analyzed.According to the simulated results,it can be found that with the increase of submerged depth of grid,the forces acting on mooring lines and bridle lines increase,while the forces on grid lines decrease;the horizontal motion amplitudes of floating collar decrease obviously,while the vertical motion amplitudes of floating collar change little.When the direction of incident wave propagation changes,forces on mooting lines and motion of net cage also change accordingly.When the propagation direction of incident wave changes from 0° to 45°,forces on the main ropes and bridle ropes increase,while the forces on the grid ropes decrease.With the increasing propagation direction of incident wave,the horizontal amplitude of the forces collar decreases,while the vertical amplitude of the floating collar has little variation.     

Numerical Simulation of Dynamic Response of Towed Systems

In this paper,the dynamic response of undersea -+towed systems is numerically simulated.Atwo body towed system is especially considered in detail.The factors influencing the heave oftowed-bodies,such as the weight of the towed-body(in sea water),the length and the weight(in sea water)per unit length of the cable between towed-bodies and towing ship,are investigated in detail.Calculationsshow that the two-body towed system can greatly increases the stability of the towed system.     

水平循环荷载作用下单桩动力特性的数值模拟

采用修正的p-y曲线方法，分析了桩基础振动过程中桩土之间由于土体塑性变形导致的桩土脱开现象，给出了计算桩土脱开现象的数值模拟方法，并据此分析计算了中国渤海湾JZ20－2MUQ平台的桩基础动力特性，得到了桩基础振动过程中桩土脱开的区域，分析了桩土之间的脱开对桩基础动力响应的影响等问题。     

Simulation of Gravity Currents Using VOF Model

By the Volume of Fluid (VOF) rnultiphase flow model two-dimensional gravity currents with three phases including air are numerically simulated in this article. The necessity of consideration of turbulence effect for high Reynolds numbers is demonstrated quantitatively by LES (the Large Eddy Simulation) turbulence model. The gravity currents are simulated for h ≠ H as well as h= H, where h is the depth of the gravity current before the release and H is the depth of the in-truded fluid. Uprising of swell occurs when a current flows horizontally into another lighter one for h ≠ H. The problems under what condition the uprising of swell occurs and how long it takes are considered in this article. All the simulated results are in reasonable agreement with the experimental results available.     

旋转式压力交换器流体能量损失研究

为探究旋转式压力交换器运行过程中流体能量损失规律,以外驱式旋转压力交换器为研究对象,采用数值模拟方法对模型的湍流耗散率进行模拟研究。研究结果表明,转子在低压区转动时,海水侧流体能量损失先降低后升高,浓盐水侧逐渐降低;转入低压密封区,流体能量损失集中在海水侧,范围逐渐向浓盐水侧扩散;进入高压区后,海水侧流体能量损失逐渐下降,浓盐水侧逐渐升高;转子在高压密封区运行时,流体能量损失集中于浓盐水侧,能量损失范围向海水侧扩散。研究结果对旋转式压力交换器结构优化具有一定指导意义。     

Numerical prediction of hydrodynamic forces on a ship passing through a lock

While passing through a lock, a ship usually undergoes a steady forward motion at low speed. Owing to the size restriction of lock chamber, the shallow water and bank effects on the hydrodynamic forces acting on the ship may be remarkable, which may have an adverse effect on navigation safety. However, the complicated hydrodynamics is not yet fully understood. This paper focuses on the hydrodynamic forces acting on a ship passing through a lock. The unsteady viscous flow and hydrodynamic forces are calculated by applying an unsteady RANS code with a RNG k-ε turbulence model. User-defined function(UDF) is compiled to define the ship motion. Meanwhile, the grid regeneration is dealt with by using the dynamic mesh method and sliding interface technique. Numerical study is carried out for a bulk carrier ship passing through the Pierre Vandamme Lock in Zeebrugge at the model scale. The proposed method is validated by comparing the numerical results with the data of captive model tests. By analyzing the numerical results obtained at different speeds, water depths and eccentricities, the influences of speed, water depth and eccentricity on the hydrodynamic forces are illustrated. The numerical method proposed in this paper can qualitatively predict the ship-lock hydrodynamic interaction. It can provide certain guidance on the manoeuvring and control of ships passing through a lock.     

Numerical Prediction of Hydrodynamic Forces on A Ship Passing Through A Lock

While passing through a lock, a ship usually undergoes a steady forward motion at low speed. Owing to the size restriction of lock chamber, the shallow water and bank effects on the hydrodynamic forces acting on the ship may be remarkable, which may have an adverse effect on navigation safety. However, the complicated hydrodynamics is not yet fully understood. This paper focuses on the hydrodynamic forces acting on a ship passing through a lock. The unsteady viscous flow and hydrodynamic forces are calculated by applying an unsteady RANS code with a RNG k?ε turbulence model. User-defined function (UDF) is compiled to define the ship motion. Meanwhile, the grid regeneration is dealt with by using the dynamic mesh method and sliding interface technique. Numerical study is carried out for a bulk carrier ship passing through the Pierre Vandamme Lock in Zeebrugge at the model scale. The proposed method is validated by comparing the numerical results with the data of captive model tests. By analyzing the numerical results obtained at different speeds, water depths and eccentricities, the influences of speed, water depth and eccentricity on the hydrodynamic forces are illustrated. The numerical method proposed in this paper can qualitatively predict the ship-lock hydrodynamic interaction. It can provide certain guidance on the manoeuvring and control of ships passing through a lock.     

Numerical Simulation and Dynamical Analysis for Low Salinity Water Lens in the Expansion Area of the Changjiang Diluted Water

The low salinity water lenses(LSWLes) in the expansion area of the Changjiang diluted water(CDW) exist in a certain period of time in some years. The impact of realistic river runoff, ocean currents and weather conditions need to be taken into account in the dynamical analysis of LSWL, which is in need of research. In this paper, the POM-σ-z model is used to set up the numerical model for the expansion of the CDW. Then LSWL in summer 1977 is simulated, and its dynamic mechanism driven by wind, tide, river runoff and the Taiwan Warm Current is also analyzed. The simulated results indicate that the isolated LSWL detaches itself from the CDW near the river mouth, and then moves towards the northeast region outside the Changjiang Estuary. Its maintaining period is from July 26 to August 11. Its formation and development is mainly driven by two factors. One is the strong southeasterly wind lasting for ten days. The other is the vertical tidal mixing during the transition from neap tide to spring tide.     

Numerical Simulation of Large Diameter Cylindrical Structure Slamming

The water entry of large diameter cylindrical structure is studied by applying numerical simulation method. The processes of different diameter cyhndrical structures impacting water with various constant velocities are calculated numerically. Thereafter, analyzed are the distribution of slamming pressure on structure during slamming course and the influence of slamming velocity and cylindrical diameter on slamming process. Furthermore, presented herein is an equation being used to forecast the peak slamming force on a large diameter cylindrical structure.     

三亚湾海岸动力演变的数值模拟研究

近年来,海岸侵蚀呈现不断加剧的趋势,给沿海地区经济社会的发展造成了极大危害。关于三亚湾海岸侵蚀过程及其动力学研究多停留在定性或半定量阶段。从海岸动力地貌学角度出发,基于沉积物迁移理论,利用数值模拟方法,定量研究了三亚湾海岸在波浪和潮流作用下的动力演变过程。计算结果重现了海水波浪的传播形态及动态特征:涨潮时,波高极值相对较大,水位随之升高,波动现象明显,波动形态复杂;落潮时,波高极值相对减小,水位也随之降低,海面相对较平静,波形态在离岸区域较单一,仅在近岸区域相对多样化。同时,数值模拟结果也很好地显示了三亚湾岸线附近的沉积或侵蚀过程特征:三亚湾西段海洋动力条件较强,沉积或侵蚀现象明显,沉积/侵蚀能力由三亚湾西段逐渐向东段减小。此外,以海洋动力学机制为基础,定量模拟了三亚湾海岸侵蚀与演变物理过程,为该地区海岸开发利用、海岸环境保护提供科学依据。     

动刚度和动力触探在强夯地基检测中的应用

随着碎石土强夯地基的推广应用，解决如何对其进行快速有效地检测，提供其准确的强度及变形参数问题，具有重要的经济及安全意义。提出了一种利用平板静力载荷试验、动力触探、地基动刚度测试三种基本手段，建立相关数学模型，主要应用后两种手段进行联合检测的新思路。并将相关数学模型以经验公式的形式进行了总结，对碎石土强夯地基的检测具有指导意义。     

Numerical simulation of longitudinal settlement of shield tunnel in the coastal city Shanghai

Until now more than 14 subway lines are in operation and some new lines are being built in the coastal city Shanghai. The longitudinal settlement of shield tunnel has significant effect on the safety of the subway operation. In this paper, the deformation of the shield tunnel and the surrounding soil were analyzed by the establishment of a three-dimensional model. The vertical displacements of four paths (Path 1 is on the ground; Path 2 is at the top of the tunnel; Path 3 is in the middle of the tunnel; Path 4 is at the bottom of the tunnel) are affected by the nature of the soil. The horizontal displacement is smaller than the vertical displacement and horizontal displacement of the clay is larger than that of the sand. The distribution of the pore pressure changes with soil properties around the tunnel. The pore pressure of the sand layer is larger than that of the clay layer at the same depth of underlying soil.     

相交圆柱摆式波能装置俘获效率数值分析

摆式波能装置具有结构简单和转化效率高等特点,本文应用AQWA 软件基于势流理论对相交圆柱摆式波能装置进行了数值模拟研究,分析了轴间距比、结构阻尼、净浮力比、水深、波浪特性及吃水深度等主要参数对相交圆柱摆式波能装置俘获效率的影响,并与直板摆式波能装置的俘获效率进行了对比。结果表明：同样条件下,相交圆柱摆式波能装置往往比直板摆式波能装置的俘获效率更高;在研究范围内,轴间距比越大俘获效率越高;潮汐导致的水深变化对底铰摆式波能装置的俘获效率具有明显的影响,在工程应用中应采取适当的措施进行处理。     

海洋盐指演化过程的数值模拟

盐指现象的数值模拟研究对理解小尺度海洋动力学过程具有十分重要的意义。本文建立了二维方腔模型,通过有限体积法求解控制方程,对盐指现象的演化过程进行了模拟计算和数值分析,在热瑞利数为(1.12～2.24)×107的变化范围内,展示并对比了不同粘滞系数、热瑞利数和盐瑞利数情况下的盐指现象,发现随着粘滞系数的增加,盐指的演变速率变慢,生成数目减少;热瑞利数的增加对盐指的演变速率具有抑制作用,而盐瑞利数的增加则对其具有促进作用。