裂隙水渗流潜水面迭代方法的探讨

针对裂隙岩体的渗流问题，引入潜水面单元的概念，探讨了裂隙网络中潜水面的迭代方法，并据此方法分析了潜水面的裂隙水渗流问题，证明该方法是可靠的。     

STUDY OF INTERACTION BETWEEN VORTICES AND A FREE SURFACE* PART I:INVISCID FLOW

Vortex method is developed to study the interaction between free surface and vortex systems. The. vortex systems, considered here, include vortex pairs, an infinite vortex sheet, and a trailing-edge vortex sheet. The computational results reproduces qualitatively the deformation of free surface under the action of vortices, which is observed in experiments.     

Coupled finite particle method with a modified particle shifting technology

The conventional SPH method has been frustrated with the low accuracy originated from the particle inconsistency. The finite particle method (FPM) is an improved SPH method with a higher‐order accuracy. However, the numerical accuracy and stability of FPM depend on the uniformity of particles. Facing the disorder particles, the conventional FPM may suffer from an ill‐conditioned corrective matrix and is difficult to conduct longtime simulations. A popular and robust particle regularization scheme is the so‐called particle shifting technology (PST), which can effectively enhance the accuracy and stability of particle methods. In the context of FPM, PST is analyzed and discussed, and a modified PST (MPST) is proposed. Modified PST saves great amount of computational cost with respect to the conventional PST and acquires better features of accuracy and stability. Finally, the coupled FPM method by combining MPST and δ‐SPH is developed to simulate a series of viscous flows. The numerical results indicate that MPST is effective in improving accuracy, stability, and efficiency of PST, and the coupled FPM is shown to be robust for simulating viscous flows and has a higher accuracy and stability.     

基于双三次B样条插值的空间结构自由曲面

双三次B样条插值曲面方法是工业造型、机械制造领域应用成熟的一种自由曲面设计方法，本在分析空间结构曲面设计现状、需求以及不足的基础上，提出了应用C^2连续的双三次B样条插值曲面方法进行空间结构自由曲面设计算法，并通过实例论证了该算法的可行性和有效性。     

可燃液体自由表面燃烧特性的数值模拟

依据小尺度汽油燃烧实验模拟法确定边界条件,采用数值模拟方法进行汽油池火燃烧模拟。数值模拟结果和实验结果具有一致性:用非稳态数值模拟的火焰热辐射随燃烧的进行逐步增加;热辐射分布以火焰的高温区分布较强;火焰中各组分如氧气消耗量、C(s)等质量浓度与燃烧时间的无量纲关系曲线与燃烧过程的温度分布一致,且遵循双曲线变化规律。采用稳态模拟方法得到不同风速条件下火焰倾角与风速之间的变化曲线,有风时火焰温度较无风时增加,且随着风速的增加而增加(实际上存在某个临界风速);有风时火焰热辐射分布随火焰的倾斜而改变,下风向热辐射明显,上风向则较低,且热辐射波及范围较无风时增大。     

铸造充型过程的数值模拟研究现状及发展

铸件充型过程计算机模拟仿真是铸造学科发展的前沿领域.分析了国内外铸造充型数值模拟的发展过程以及目前应用的最前沿数值模拟方法,论述了铸造充型模拟的数学模型、计算方法和实验验证方法,并提出了数值模拟现存的主要问题,阐述了充型过程数值模拟的发展趋势.     

三峡船闸进水口三维水动力特性数值模拟

 以三峡船闸进水口输水系统为研究背景，建立三峡船闸进水口的数值几何模型；同时根据进水口水流具有自由表面及较大弯曲壁面的流动特性，建立计算模型和网格边界。在此基础上，分别对三峡船闸进水口在145.0 m及175.0 m（正常蓄水位）两种库水位条件下输水运行进行了数值模拟，其计算结果与物理模型及原型观测数据对比，较为吻合，说明该数值模型对研究上游引航道通航水流条件及输水廊道的水力特性，具有较好的效果。     

激光快速成形过程中熔池形态的演化

采用高速摄影技术对激光快速成形过程中液态熔池的形成及其演化过程进行了实时观察。结果发现,以一定速度向前运动的激光束辐照基材时,基材表面开始熔化并形成液态熔池,经过一个较短的时间间隔(约1．0 s)后熔池深度增大至一定值,熔池长度则围绕一恒定值波动。以恒定送粉率向熔池中连续送进金属粉末时,熔池的长度和宽度逐渐减小,熔池寿命缩短。同时熔池后沿不断抬高即熔覆层厚度不断增加,最大熔深处熔池自由表面法向和激光束轴线之间的夹角由几度逐渐增大到20°～30°左右。熔池自由表面发生周期性的变化,实验观察到熔池后沿有周期性的“岛状凸起”出现和消失现象。数值计算结果证实这主要是熔池中熔体在表面张力梯度下引起的强制对流作用的结果。     

基于STEP-NC的自由曲面刀具路径生成术的研究

在详细地分析了STEP-NC程序相对于G/M代码差异及优越性的基础上,深入地对基于STEP-NC的CNC系统中关键技术——刀具路径生成技术进行了研究。本文以自由曲面为例,首先分析了自由曲面如何在STEP-NC程序的表述,然后从STEP-NC程序中提取有用的信息自动生成刀具路径,最后采用仿真来验证该方法的正确性。