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一个浅水波方程的Semi—Lagrangian—半隐式格式试验方案
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作者 卢敬华 赵邦杰 《成都信息工程学院学报》 1989年第2期14-25,共12页
在正形投影坐标系下,半拉格朗日法与半隐式法相结合积分浅水波方程导出的模式,用一小时的时间步长,是无条件稳定。我们作了一个60小时的实例时间积分,计算稳定。半隐式积分格式导致求解一个赫姆霍茨方程,为比较其高低精度的优劣,我们提... 在正形投影坐标系下,半拉格朗日法与半隐式法相结合积分浅水波方程导出的模式,用一小时的时间步长,是无条件稳定。我们作了一个60小时的实例时间积分,计算稳定。半隐式积分格式导致求解一个赫姆霍茨方程,为比较其高低精度的优劣,我们提出在空间上用二阶精度和四阶精度解赫姆霍茨方程的超松驰法,同时,作了有无地形的试验。应该注意列,半拉格朗日法含有大量的插值,因而,在每一步时间步长里此积分格式比通常的欧拉法含有更多的计算,但是每一时间步长的计算量的增加却从使用很大的时间步长得到了更多的补偿。 展开更多
关键词 数值天气预报 半拉格朗日法 半隐式法 浅水波方程
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岩石非线性细观损伤-塑性耦合本构模型及其数值实现
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作者 张志镇 滕业奇 +4 位作者 周睿 张辉 徐珂 尚晓吉 高峰 《岩石力学与工程学报》 EI CAS CSCD 北大核心 2024年第6期1425-1442,共18页
为了体现岩石在压缩过程中的压剪破坏模式,解决传统多尺度岩石损伤力学本构模型不能描述剪切弱化的问题,在多尺度岩石损伤力学框架内,通过考虑局部应力Lode角对屈服函数的影响,引入局部莫尔-库仑塑性屈服函数,建立一个新的岩石非线性细... 为了体现岩石在压缩过程中的压剪破坏模式,解决传统多尺度岩石损伤力学本构模型不能描述剪切弱化的问题,在多尺度岩石损伤力学框架内,通过考虑局部应力Lode角对屈服函数的影响,引入局部莫尔-库仑塑性屈服函数,建立一个新的岩石非线性细观损伤-塑性耦合本构模型。推导出本构模型在常规三轴压缩情况下应力-应变的解析解,进而给出本构模型所有参数的标定方法。采用优化后的半隐式解耦算法将本构模型写入LS-DYNA材料库,通过单元测试验证算法的有效性和收敛性,并对石灰岩三轴压缩力学特性进行模拟,数值模拟结果和试验数据具有较好的一致性。最后,进行本构模型参数敏感性分析,得出模型参数对岩石峰值应力、峰值应变、脆延转变等力学行为的影响规律。所建立的本构模型不需要引入额外的硬化/软化函数,显著减少了模型参数的数量,且参数具有严格的标定方法,采用关联流动法则即可完成对轴向、横向及剪切非线性力学行为的准确描述;优化后的半隐式解耦算法收敛性较好,所编译的LS-DYNA求解器计算过程稳定,且计算速度显著快于岩石传统现象学模型,这对于本构模型的实际应用具有重要意义。 展开更多
关键词 岩石力学 细观力学 损伤-摩擦耦合模型 局部应力Lode角 半隐式解耦算法
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Error Estimate for Semi-implicit Method of Sphere-Constrained High-Index Saddle Dynamics
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作者 Lei ZHANG Pingwen ZHANG Xiangcheng ZHENG 《Chinese Annals of Mathematics,Series B》 SCIE CSCD 2023年第5期765-780,共16页
The authors prove error estimates for the semi-implicit numerical scheme of sphere-constrained high-index saddle dynamics,which serves as a powerful instrument in finding saddle points and constructing the solution la... The authors prove error estimates for the semi-implicit numerical scheme of sphere-constrained high-index saddle dynamics,which serves as a powerful instrument in finding saddle points and constructing the solution landscapes of constrained systems on the high-dimensional sphere.Due to the semi-implicit treatment and the novel computational procedure,the orthonormality of numerical solutions at each time step could not be fully employed to simplify the derivations,and the computations of the state variable and directional vectors are coupled with the retraction,the vector transport and the orthonormalization procedure,which significantly complicates the analysis.They address these issues to prove error estimates for the proposed semi-implicit scheme and then carry out numerical experiments to substantiate the theoretical findings. 展开更多
关键词 Saddle point Constrained saddle dynamics Solution landscape semiimplicit Numerical analysis
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A VERTICAL 2D MATHEMATICAL MODEL FOR HYDRODYNAMIC FLOWS WITH FREE SURFACE IN σ COORDINATE 被引量:15
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作者 ZHANG Jing-xin LIU Hua XUE Lei-ping 《Journal of Hydrodynamics》 SCIE EI CSCD 2006年第1期82-90,共9页
Numerical models with hydrostatic pressure have been widely utilized in studying flows in rivers, estuaries and coastal areas. The hydrostatic assumption is valid for the large-scale surface flows where the vertical a... Numerical models with hydrostatic pressure have been widely utilized in studying flows in rivers, estuaries and coastal areas. The hydrostatic assumption is valid for the large-scale surface flows where the vertical acceleration can be ignored, but for some particular cases the hydrodynamic pressure is important. In this paper, a vertical 2t) mathematical model with non-hydrostatic pressure was implemented in the σ coordinate. A fractional step method was used to enable the pressure to be decomposed into hydrostatic and hydrodynamic components and the predictor-corrector approach was applied to integration in time domain. Finally, several computational cases were studied to validate the importance of contributions of the hydrodynamic pressure. 展开更多
关键词 vertical 2D model free surface flow semiimplicit NON-HYDROSTATIC
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THE FORMULATION OF A PERFECT SQUARE CONSERVATIVE SEMI-IMPLICIT TIME DIFFERENCE SCHEME AND ITS PRELIMINARY CHECK 被引量:3
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作者 钟青 《Chinese Science Bulletin》 SCIE EI CAS 1992年第6期497-502,共6页
Quantitative studies of scientific problems require solving correspondent mathematical models. Although a great deal of mathematical models of evolutional problems are set up under continuous space-time meaning, they ... Quantitative studies of scientific problems require solving correspondent mathematical models. Although a great deal of mathematical models of evolutional problems are set up under continuous space-time meaning, they usually had to be solved numerically after space-time discretization because nonlinear mathematical models except some 展开更多
关键词 nonlinear SEMI-IMPLICIT perfecr SQUARE CONSERVATIVE time difference scheme COMPUTATIONAL finstability COMPUTATIONAL accuracy
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