SIMULATION OF TANK SLOSHING BASED ON OPENFOAM AND COUPLING WITH SHIP MOTIONS IN TIME DOMAIN

Tank sloshing in ship cargo is excited by ship motions, which induces impact load on tank wall and then affects the ship motion. Wave forces acting on ship hull and the retardation function are solved by using three-dimensional frequency domain theory and an impulse response function method based on the potential flow theory, and global ship motion is examined coupling with nonlinear tank sloshing which is simulated by viscous flow theory. Based on the open source Computational Fluid Dynamics (CFD) development platform Open Field Operation and Manipulation (OpenFOAM), numerical calculation of ship motion coupled with tank sloshing is achieved and the corresponding numerical simulation and validation are carried out. With this method, the interactions of wave, ship body and tank sloshing are completely taken into consideration. This method has quite high efficiency for it takes advantage of potential flow theory for outer flow field and viscous flow theory for inside tank sloshing respectively. The numerical and experimental results of the ship motion agree well with each other.     

TIME DOMAIN SOLUTION OF UNSTEADY FLOW AROUND A SHIP

The unsteady flow around a ship advancing at constant speed is studied in time domain using a higher-order boundary element method. The Rankine source is employed and the ship hull and free surface are discretized into 8-node isoparametric elements. A modified Green formula is used to overcome the numerical difficulty arising from the singular or quasi-singular integrals in the integral equation. In the case of τ> 0. 25, a rigid wall condition is applied to the upstream and a numerical beach is applied downstream to absorb the outgoing waves. The numerical results are satisfactory, compared with the experimental results.     

NUMERICAL SIMULATIONS OF WAVE-INDUCED SHIP MOTIONS IN TIME DOMAIN BY A RANKINE PANEL METHOD

A time domain prediction of wave-induced ship motions by a Rankine panel method is investigated. Linear boundary conditions on free surface and mean wetted body surface are adopted, while the numerical damping method is used for the radiation conditions. The motions of two ships in regular head waves are computed by the present method. The related numerical results are compared with the experiment data and those from linear strip theory. The comparison shows satisfactory agreements for pitch and heave transfer functions.     

WAVE MAKING COMPUTATION IN TIME DOMAIN FOR MULTI-HULL SHIPS

1. INTRODUCTION For high-speed displacement ships, the wave making at the free surface is an important hydro- dynamic performance. The wave making reduction has attracted more attention for ship designers. The ship wave resistance and ship hull form improvement have been widely investigated. The thin ship theory adopting the Havelock source distribution on the ship centerline plane can be used to analyze the ship wave making profile and the ship wave resistance may be obtained by ship wav…     

HYDROELASTIC VIBRATIONS AND LIQUID SLOSHING SUPPRESSION IN A RECTANGULAR TANK WITH ELASTIC SPACER

In this paper, the couple vibration of liquid and elastic spacer in a rectangular tank is investigated. Two different velocity potential functions corresponding respectively to the liquid above and below the elastic spacer are assumed.Complicated boundary conditions corresponding to two velocity potential functions and vibrations of elastic spacer are given. Using the method of energy, the equation of couple frequency is obtained. Through numerical computation the natural frequencies that change according to the location and stiffness of the spacer are shown.     

COMPUTATIONAL RESEARCH ON WAVE MAKING OF MOVING WIGLEY HULL IN TIME DOMAIN

Based on Green＇s theorem, a time domain numerical model was constructed to simulate wave making phenomenon caused by a moving ship. In this article, the Rankine sources and dipoles were placed on boundary surfaces （i.e., the ship surface and free surface）, and a time-stepping scheme was employed. Its unique characteristic is that steady state can be realized from initial value by employing the time-stepping scheme and unsteady free surface conditions. In time domain, if the results of unsteady flow problem tend to data stabilization after many time steps of computation, they could be regarded as the data of steady ones. This model could be employed to steady or unsteady problems. Theoretical reasoning and computational process of this method was described in detail The linear and nonlinear boundary conditions on body surface were studied, and the relative means to realize these boundary conditions in iterative computation were also discussed. Some proper parameters about the model of the Wigley hull were determined by many numerical tests, and their influences on wave making resistance and wave pattern were discussed. According to the comparison between numerical results and data available in relative references, the method used in this work is proven to be a reliable method in time domain. And the lattice reorganization in every time step computation is a feasible numerical approach.     

非平稳时间序列法在特殊裂缝观测资料分析中的应用

根据大坝裂缝开度实测资料的特点，将裂缝开度{Xt}看成一系列时刻t1,t2,…，tn得到的时间序列，采用基于滑动平衡模型MA（q）的非平稳时间序列法，对其进行模型识别，参数估计和新息预报。通过概率分布函数对其规律性进行统计描述，克服了常规回归分析方法的不足，计算结果表明，该方法预报精度高，是一种行之有效的方法。     

NUMERICAL INVESTIGATION OF SEABED INTERACTION IN TIME DOMAIN ANALYSIS OF MOORING CABLES

1. INTRODUCTION Seabed interaction of mooring cables influences the dynamic behavior of the mooring system (see Fig.1). As moored structures are widely used in the offshore oil and gas industry, there is a continuing need to improve the designs of such st…     

最优权组合模型与参数优化在安全监测分析中的应用

采用最优加权法配合参数优化建立组合预测模型 ,对某电站厂房机组平台作垂直位移分析。实例计算证实了所建模型的有效性 ,为一元或多元非线性建模提供了一条可行途径。     

用交集域优选法辨识堆石坝材料参数

应用岩土力学、数理统计等理论 ,对鲁布革风化料心墙堆石坝变形观测资料进行了细致的分析 ,建立了数学模型 ,并将变形合理分解为填筑分量、水压分量和时效分量。通过对材料各参数与变形之间的关系分析和大量的有限元计算 ,按照交集域优选法的思想、辨识鲁布革堆石坝各区材料的非线性参数 ,结果令人满意     

THREE-DIMENSIONAL MODELLING FOR LUBRICATION WITH REFERENCE TO HUMAN JOINTS

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A TIME DOMAIN INVESTIGATION ON THE HYDRODYNAMIC RESO-NANCE PHENOMENA OF 3-D MULTIPLE FLOATING STRUCTURES

A 3-D time domain method is developed to investigate the gap influence on the wave threes for 3-D multiple floating structures. Special hydrodynamic resonance due to small gaps between multiple floating structures on wave forces is examined. Strong and complicate hydrodynamic interactions between the floating bodies are observed and the numerical computations have proved the existence of the sharp peak force response on each floating body at some special resonant wave numbers. By comparison with the results from the frequency domain technique, the results obtained from the time domain method reveal the similar resonant phenomena and hydrodynamic interaction. The resonant wave numbers are also proved around kL-nπ （n = 1,2 ……∞） with a corresponding frequency shift. The strong hydrodynamic interaction feature is practically significant for the design of module structures and the links （connection） in whole the floating body system.     

THE ANALYSIS OF THE SEPARATED LAYERS ALGORITHM BY DOMAIN DECOMPOSITION METHOD

From the principle of of the Domain Decomposition Method (DDM), we analyse the 2nd-order linear elliptic partial differential problems and link the Separated-Layers Algorithm (SLA) with DDM. The mathematical properties of SLA and numerical example are presented to obtain satisfactory computation results. For general linear differential ones, also are the structure of SLA and its characteristics discussed.     

NUMERICAL RESEARCH ON UNSTEADY SHIP WAVE-MAKING PROBLEMS IN TIME-DOMAIN

A time-domain Kelvin source high-order panel method based on NURBS is developed and applied to solve the unsteady wave-making problems. Numerical results of instant wave resistance and free surface elevation are presented and compared with the availaby results by other authors, for submerged spheroid and sphere beneath the free surface and for surface ship of Wigley models moving with unsteady speed,The agreement is satisfying.     

TIME-DOMAIN ANALYSIS OF WAVE FORCES ON SHIPS WITH FORWARD SPEED

Analyses of wave forces on Wigley and Series 60 ships at forward speedare presented in time domain which is based on a free surface transient Green functionwith linearized condition. The main effort focus on the investigation of the numerical sta-bility of time stepping calculation and the waterline intergal contribution to the excitingforces. Numerical study shows that the stable results can be obtained when a wall-sided as-sumption is used at the stern only and the effect of waterline can be neglected. Compar-isons have been made between the present time domain calculations and other works. Nu-merical results for the added resistance on a C_B=0.8 ship in short waves are presentedbased on the assumption that the steady disturbance of ship hull can be neglected.     

因素分析模型在拱坝观测数据分析中的研究与应用

针对拱坝安全监测中大量的观测数据以及数据之间复杂的相关性，从全坝多测点的测值所形成的相关矩阵中提取整体因素信息，分析各观测变量之间的相互关系，归纳出测量本质相同的变量，使分散复杂的观测数据成果简洁化、整体化，从而为观测资料的整体分析提供一种多元统计分析方法。     

APPLICATION OF LBM-SGS MODEL TO FLOWS IN A PUMPING-STATION FOREBAY

A 2-D Lattice Boltzmann Method (LBM) coupled with a Sub-Grid Stress (SGS) model is proposed and validated by flows around a non-submerged spur dike in a channel. And then the LBM-SGS model is further applied to flows in a pumping-station forebay. Shallow water equations are numerically solved by the LBM and the turbulence can be taken into account and modeled efficiently by the Large Eddy Simulation (LES) model. The bounce-back scheme of the non-equilibrium part of the distribution function is used at the inlet boundary, the normal gradient of the distribution function is set as zero at the outlet boundary and the bounce-back scheme is applied to the solid wall to ensure non-slip boundary conditions. Firstly, the model successfully predicts the flow characteristics around a spur dike, such as circulating flow, velocity and water depth distributions. The results are verified by the experimental data and compared to the results obtained by conventional Smagoringsky Model (SM) of LES. Finally, the LBM-SGS model is used to further predict the flow characteristics in a forebay, such as secondary flow and water level. The comparisons show that the model scheme has the capacity to simulate complex flows in shallow water with reasonable accuracy and reliability.     

基于模型筛选法的卡尔曼滤波法在大坝变形分析中的应用

以模型筛选法为基础，将筛选出的变形误差最小的模型的模型参数作为状态向量，用卡尔曼滤波法进行大坝变形分析，实例计算表明，这种方法能够提高模型的拟合及预报精度。     

SECONDARY INSTABILITY WITH RESPECT TO SPATIAL GROWING THREE－DIMENSIONAL SUBHARMONIC DISTURBANCES IN BOUNDARY LAYER FLOW WITH SUCTION

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A TIME-DOMAIN METHOD TO PREDICT SHIP MOTIONS IN OBLIQUE SEAS AT FORWARD SPEEDS

Time-domain analysis is used to predict wave loading and motion responses for a ship travelling at a constant speed in regular oblique waves.The combined diffraction and radiation perturbations,caused by the steady forward speed of the ship and her motions,are considered as a distribution of normal velocities on the wetted hull surface.The ship-hull boundary condition is exactly fulfilled by expressing the fluid normal velocities as a finite series in terms of the body geometry and the incident wave potential.As far as the authors are aware,no similar work is published todate. The new theory is applied to predict forces and motions at forward speed for a Wigley ship-hull in head waves and a catamaran-ferry in oblique waves.Predictions are compared with published theoretical and experimental results for the Wigley ship-hull,and the comparison is good.For the catamaran,a self-propelled model is built and tested in the large towing tank and seakeeping basin of the China Ship Scientific Research Centre,Wuxi