三维N-S方程混合有限分析多重网格方法

提出了一种求解三维定常不可压N-S方程的混合有限分析多重网格方法(HFA-FMG).以三维方腔流动作为算例,计算表明提出的数值格式能极大地节省计算工作量且稳定有效.三维方腔流动的模拟成果较好地表现方腔内复杂的流动特征并和其他成果吻合.     

间断水波在梯级水库中的传播

基于矢通量分裂得到了一维浅水方程组的隐式守恒有限差分格式,并对有底坡、有摩阻的梯级水库同时溃坝和相继溃坝的溃坝波传播进行了数值模拟。对数值结果作了分析。结果合理,方法有效可行。     

含油水各向异性孔隙介质中地震波传播方程

油气勘探的重点是寻找油气储层的分布 ,而地下油气的存在必然对地震记录产生影响。传统的地震波理论是建立在纯弹性固体基础之上 ,没有考虑固体中所含的流体 ,因此 ,它难以研究含油水岩石的物理性质 ,如岩石的渗透率和孔隙度、油水粘度。从固、液介质系统能量和本构方程出发 ,推导出固体、油相和水相的动力学方程 ,进而建立起含油水两相流体各向异性孔隙介质的地震波传播方程。该方程包括有岩石和油水的物理参数 ,更适合于油田的勘探和开发。     

Plasticity model for sand under small and large cyclic strains: a multiaxial formulation

This paper presents the multiaxial formulation of a plasticity model for sand under cyclic shearing. The model adopts a kinematic hardening circular cone as the yield surface and three non-circular conical surfaces corresponding to the deviatoric stress ratios at phase transformation, peak strength and critical state. The shape of the non-circular surfaces is formulated in accordance with the experimentally established failure criteria, while their size is related to the value of the state parameter ψ. To simulate cyclic response under small and large shear strain amplitudes without a change in model parameters, it was found necessary to introduce: (a) a non-linear hysteretic (Ramberg–Osgood type) formulation for the strain rate of elastic states and (b) an empirical index of the effect of fabric evolution during shearing which scales the plastic modulus. This index is estimated in terms of a macroscopic second-order fabric tensor, which develops as a function of the plastic volumetric strain increment and the loading direction in the deviatoric plane. Comparison of simulations to pertinent data from 27 resonant column, cyclic triaxial and cyclic direct simple shear tests provide a measure for the overall accuracy of the model.     

The effect of ferromagnetism on the equation of state of Fe3C studied by first-principles calculations

First-principles calculations have been used to determine the equation of state of Fe₃C in both its low-pressure magnetically ordered and high-pressure non-magnetically ordered states; at 0 K the ferromagnetic transition was found to occur at about 60 GPa. In the high pressure, non-magnetically ordered regime at 0 K the material may be described by a Birch-Murnaghan third-order equation of state with V₀=8.968(7) ų per atom, K₀=316.62(2) GPa and K′=4.30(2). At atmospheric pressure the ferromagnetic phase transition in Fe₃C occurs at ∼483 K; preliminary measurements of the thermal expansion by powder neutron diffraction show that this transition produces a large effect on thermoelastic properties. The volumetric thermal expansion coefficient in the paramagnetic phase was found to be 4.34×10⁻⁵ K⁻¹ at T∼550 K. By applying a thermal expansion correction to the calculated equation of state at 0 K, predicted values for the density and adiabatic incompressibility of this material at core pressures and temperatures were obtained. These results appear to be sufficiently different from seismological data so as to preclude Fe₃C as the major inner core-forming phase.     

Equation of state of gold and its application to the phase boundaries near 660 km depth in Earth’s mantle

The pressure-volume-temperature equation of state (EOS) of gold is fundamental to high-pressure science because of its widespread use as an internal pressure standard. In particular, the EOS of gold has been used in recent in situ multi-anvil press studies for determination of phase boundaries related to the 660-km seismic discontinuity. These studies show that the boundaries are lower by 2 GPa than expected from the depth of the 660-km discontinuity. Here we report a new P-V-T EOS of gold based on the inversion of quasi-hydrostatic compression and shock wave data using the Mie-Grüneisen relation and the Birch-Murnaghan-Debye equation. The previously poorly constrained pressure derivative of isothermal bulk modulus and the volume dependence of Grüneisen parameter (q=d lnγ/d ln V) are determined by including both phonon and electron effects implicitly: K′_0T=5.0±0.2 and q=1.0±0.1. This combined with other accurately measured parameters enables us to calculate pressure at a given volume and temperature. At 660-km depth conditions, this new EOS yields 1.0±0.2 GPa higher pressure than Anderson et al.’s EOS which has been used in the multi-anvil experiments. However, after the correction, there still exists a 1.5-GPa discrepancy between the post-spinel boundary measured by multi-anvil studies and the 660-km discontinuity. Other potential error sources, such as thermocouple emf dependence on pressure or systematic errors in spectroradiometry, should be investigated. Theoretical and experimental studies to better understand electronic and anharmonic effects in gold at high P-T are also needed.     

水气二相流方程的一种离散数值解法

提出了水气二相流方程的一种数值解法.在利用有限元方法求解水气二相流方程时,引入了离散Newton迭代方法,用于非线性有限元方程组的线性化处理,将这一步计算的收敛阶由原有研究的线性收敛提高到平方收敛,并避免了直接应用Newton迭代方法给编程带来的不便.同时在求解两相的有限元方程组时,采用两相方程组并行迭代的方法,与联立计算相比节省了大量的内存空间.     

非规则网格下二维浅水流动的数值模拟

建立了一种在非规则结构化网格上求解平面二维浅水流动的有限体积方法。通过采用地形在离散网格内双线性变化及离散网格界面间地形连续的地形逼近方法和应用可以有效处理间断问题的Roe格式来离散浅水方程中的对流项,并通过VanLeer提出的状态插值法提高格式精度。在计算原始变量在网格内的插值梯度时,采用最小二乘方法求变量的最优梯度代替差分计算梯度,从而可采用任意形状的不规则四边形网格离散计算域。计算实例表明,该方法能够计算间断问题并能够处理各种复杂流态的过渡,具有较好适应性和计算精度,能够满足不同实际问题的计算要求。     

宝钢引水库大坝水平位移监测评价和变形分析

本文对宝钢引水库大坝的水平位移监测网的布设方案,采用灵敏度和可靠性准则进行了网的优化设计计算,从监测网的质量准则出发,对布网方案作了若干探讨。从二十五期观测资料中选出十三期进行了水平位移计算和变形的几何分析。指出,在变形分析中正确选取基准的重要意义和据多期位移值进行变形预报的一些方法,并定性地讨论了该大坝变形的物理解释。本文所作的工作对类似大坝的水平位移监测和成果处理具有实际意义。     

地震数据互相关驱动的多道反演方法

地震反演是储层定量描述和地震油气识别的关键技术,反演结果在复杂构造区域的横向连续性和保真性是影响地震资料定量解释精度的重要因素.基于此,本文发展了地震数据互相关驱动的多道反演方法.考虑地层反射系数与地震数据在结构上具有相似性的特点,基于地震数据互相关描述地层反射系数的结构特征,并将其作为多道地震反演的横向约束条件;此外,为改善地震数据本身横向连续性差对反演结果的影响,在目标泛函的惩罚项中引入局部优化算子,构建了一个易于求解的多道地震反演目标泛函.与常规多道地震反演方法相比,本文方法能够设计更合理、更符合实际情况的横向约束算子,提高反演结果的横向连续性,并且能有效降低地震资料质量对反演结果的影响.模型测试和实际应用验证了本方法的可靠性和稳定性.