用格子Boltzmann方法模拟平板层流边界层流动

本文应用格子Boltzmann方法模拟了平板层流边界层流动。考虑到平板边界的影响，我们对模型进行了修正，在标准格子Boltzmann方程中引入压力修正项。该项满足一定的假定条件，从而消除了压缩性引起的偏差。作为算例，我们用修正的模型计算了平板层流边界层流动，并与经典的Blasius解及Lavallee的格子气自动机结果进行了比较，结果是可以接受的。     

空泡噪声的数值研究

空泡噪声是一个非线性动边界的声辐问题，作者针对这个特点，提出了一种新的数值方法-混合边界元法，本文应用混合边界元法对无界流场、自由面或固壁面附近空泡溃灭过程辐射的噪声进行计算，得到了空泡在不同情况下溃灭辐射声音的特征，结果显示混合边界元方法在这类动边界声辐射问题上，能体现出声音传播的延迟效应，体现出液体压缩性对声压峰值的影响，作者认为混合边界法在处理这类动边界声辐射问题上有着很好的应用前景。     

不确定性边界问题的预网格剖分边界拟合方法

本文提出了一种处理不确定性边界问题的预网格剖分边界拟合方法，并对其基本思想和算法进行了比较详细的阐述。利用本文提出的方法编写相关计算机程序对一复杂曲线形态的动边界实例处理结果显示：该方法对复杂边界具有较好的拟合能力，边界附近网格质量较好，能够有效减少数值计算前处理的工作量。同时在节省计算机内存以及保证网格质量等方面都具有明显的优越性。     

辽东湾顶极浅海潮流数值计算

针对辽东湾顶的复杂地形，本文使用有限元方法离散浅水波动方程。对计算区域采用三角单元剖分，对水位和流速用线性插值函数逼近，应用动边界技术模拟了潮滩随水位变化而干出或淹没，对传统的底摩擦公式进行了改进，从而解决了在计算很浅的水域时，可能出现的数值不稳定问题。本文的计算值与实测资料符合良好。     

高拱坝地震响应时程分析

采用有限元结合三维粘弹性局部人工边界的动接触地震波动模拟方法建立拱坝一地基一库水的有限元计算模型,研究库水对结构振动频率和振型的影响.并借助APDL语言实现粘弹性人工边界、动水压力及地震波的自动输入模块.对拱坝-地基-库水联合作用下的结构进行抗震计算时程分析.计算结果为优化坝体结构的动力特性和抗震设计提供参考.     

考虑动水压力的土石坝三维动力反应分析

本文用空间有限元与边界元相结合的方法分析土石坝与水体间的动力相互作用问题,考虑地震荷载和动水压力共同作用时对土石坝进行三维动力反应分析。还对动水压力问题进行了一些试验研究,在土石坝动力计算中采用了部分试验结果,并结合工程实例对计算方法进行了比较分析。     

边界元法求解振动边界的动水压力

本文研究了平面理想不可压缩流体在其周围的固体边界作微幅振动条件下,流场计算的边界元方法。通过刚性坝面不同倾角以及刚性闸门的四种边界条件在不同开度时的动水压力计算,并与已有成果对比分析,说明边界元方法在进行水工结构——流体相互作用的研究中是一种实用的数值计算方法。特别是用于闸门泄水定常流场下,由闸门边界振动而产生的非定常流场所确定的闸门上压力分布是比较合理的。     

波浪对三维浮体的二阶作用

本文通过求解二阶势的方法对波浪与任意形状三维物体的相互作用问题做了研究，波浪运动的二阶势应用高阶边界元方法进行计算，为了高阶边界元法的应用，本文给出了一个无速度势二阶空间导数，无奇异积分的新的积分方程。     

采用边界元法确定坝基面渗透压力

由于边界单元法只需在边界上剖分单元，且容易处理无限边界问题，所以在计算坝基面渗透压力时较有限元法具有明显的优势。介绍了坝基面渗透压力的计算理论及其边界元数值算法，并给出了应用算例。由算例分析可以看出，采用边界元法计算坝基面渗透压力，计算程序简单，占用计算机内存少，计算速度快，且计算精度较高。     

人工粘性、动边界及其在河口二维水流计算中的应用

本文就附加人工粘性以增强计算格式的稳定性和引用动边界以适应平面边界随潮位的变化这两个问题进行了分析。综合前人研究的基础上,建成了几种平面二维人工粘性项的结构形式,介绍了动边界的两种处理方式。分析了利用人工粘性抑制由于动边界的引用造成的局部不稳定的问题。通过对某电站升船机下游引航道非恒定的计算和长江口南支潮流场的计算试用,结果是令人满意的。     

A radial basis function for reconstructing complex immersed boundaries in ghost cell method

It is important to track and reconstruct the complex immersed boundaries for simulating fluid structure interaction problems in an immersed boundary method(IBM). In this paper, a polynomial radial basis function(PRBF) method is introduced to the ghost cell immersed boundary method for tracking and reconstructing the complex moving boundaries. The body surfaces are fitted with a finite set of sampling points by the PRBF, which is flexible and accurate. The complex or multiple boundaries could be easily represented. A simple treatment is used for identifying the position information about the interfaces on the background grid. Our solver and interface reconstruction method are validated by the case of a cylinder oscillating in the fluid. The accuracy of the present PRBF method is comparable to the analytic function method. In ta flow around an airfoil, the capacity of the proposed method for complex geometries is well demonstrated.     

FULLY NONLINEAR WAVE COMPUTATIONS FOR ARBITRARY FLOATING BODIES USING THE DELTA METHOD

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Development of Cartesian grid method for simulation of violent ship-wave interactions

We present a Cartesian grid method for numerical simulation of strongly nonlinear phenomena of ship-wave interactions. The Constraint Interpolation Profile(CIP) method is applied to the flow solver, which can efficiently increase the discretization accuracy on the moving boundaries for the Cartesian grid method. Tangent of Hyperbola for Interface Capturing(THINC) is implemented as an interface capturing scheme for free surface calculation. An improved immersed boundary method is developed to treat moving bodies with complex-shaped geometries. In this paper, the main features and some recent improvements of the Cartesian grid method are described and several numerical simulation results are presented to discuss its performance.     

Numerical modeling of sediment transport based on unsteady and steady flows by incompressible smoothed particle hydrodynamics method

The purpose of the present paper is to introduce a simple two-part multi-phase model for the sediment transport problems based on the incompressible smoothed particle hydrodynamics(ISPH) method. The proposed model simulates the movement of sediment particles in two parts. The sediment particles are classified into three categories, including the motionless particles, moving particles behave like a rigid body, and moving particles with a pseudo fluid behavior. The criterion for the classification of sediment particles is the Bingham rheological model. Verification of the present model is performed by simulation of the dam break waves on movable beds with different conditions and the bed scouring under steady flow condition. Comparison of the present model results, the experimental data and available numerical results show that it has good ability to simulate flow pattern and sediment transport.     

计算流体动力学(CFD)在建筑排水系统中的应用

建筑排水系统的设计依据是最大使用限度理念,该理念由概率论和恒定流理论发展而来.这种基于恒定流理论的现有方法,对排水立管流态、瞬态压强传播机理、系统内气体运动模式、虹吸雨水排水系统初始阶段的管道水流状态等问题的分析难以取得有效进展,而对排水系统内部非恒定水流运动情况的详细分析已成为该领域的研究趋势.介绍了研究建筑排水系统内气水运动模式的计算流体动力学(CFD)方法,并总结了CFD在国外排水系统中的应用情况.     

NUMERICAL STUDY OF SQUARE-STERN SHIP WAVE IN SHALLOW WATER

This paper employed shallow water equations with moving pressure to calculate water waves generated by a square-stern ship in shallow water. The moving ship is considered as moving pressure on free surface. The finite element method with moving grids is used to solve the shallow water equations based on wave equation model [3]. A non-reflection boundary condition [5]is imposed on open boundaries surrounding the ship. 3-D surface elevations, depth-averaged horizontal velocities are presented. The numerical solutions are physically reasonable. It is found that wave resistance coefficients, draftchange and pitch angle vary rapidly in neighborhood of critical flow (Fh=u/ gh= 0. 9 -1. 1). The numerical results also indicate that the wave resistance coefficients, draft change and pitch angle of square-stern ship are larger than those of sharp-stern ship with the same hull structure at the same speed.     

Numerical simulation of two-dimensional viscous flows using combined finite element-immersed boundary method

In this paper, a method that combines the characteristic-based split finite element method(CBS-FEM) and the direct forcing immersed boundary(IB) method is proposed for the simulation of incompressible viscous flows. The structured triangular meshes without regarding the location of the physical boundary of the body is adopted to solve the flow, and the no-slip boundary condition is imposed on the interface. In order to improve the computational efficiency, a grid stretching strategy for the background structured triangular meshes is adopted. The obtained results agree very well with the previous numerical and experimental data. The order of the numerical accuracy is shown to be between 1 and 2. Moreover, the accuracy control by adjusting the number density of the mark points purely at certain stages is explored, and a second power law is obtained. The numerical experiments for the flow around a cylinder behind a backward-facing step show that the location of the cylinder can affect the sizes and the shapes of the corner eddy and the main recirculation region. The proposed method can be applied further to the fluid dynamics with complex geometries, moving boundaries, fluid-structure interactions, etc..     

Numerical method for multi-body fluid interaction based on Immersed Boundary Method

A Cartesian grid based on Immersed Boundary Method (IBM), proposed by the present authors, is extended to unstructured grids.The advantages of IBM and Body Fitted Grid (BFG) are taken to enhance the computation efficiency of the fluid structure interaction in a complex domain.There are many methods to generate the BFG, among which the unstructured grid method is the most popular.The concept of Volume Of Solid (VOS) is used to deal with the multi rigid body and fluid interaction.Each body surface is represen...     

工程中液面波动的数值模拟

本文研究数值模拟含有自由表面的三维非定常流动的表面波动情况。运用部分单元法的概念成功地 各种复杂形状的边界以及复杂的边界条件和流场内部的障碍物，运用ＶＯＦ方法踪自由液面。     

NUMERICAL SOLUTION FOR UNSTEADY 2－D FLOW USING THE TRANSFORMED SHALLOW WATER EQUATIONS

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