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Comparison of perfectly matched layer and multi-transmitting formula artificial boundary condition based on hybrid finite element formulation
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作者 李宁 谢礼立 翟长海 《Acta Seismologica Sinica(English Edition)》 CSCD 2007年第6期684-695,共12页
The theory of perfectly matched layer (PML) artificial boundary condition (ABC), which is characterized by absorption any wave motions with arbitrary frequency and arbitrarily incident angle, is introduced. The co... The theory of perfectly matched layer (PML) artificial boundary condition (ABC), which is characterized by absorption any wave motions with arbitrary frequency and arbitrarily incident angle, is introduced. The construction process of PML boundary based on elastodynamic partial differential equation (PDE) system is developed. Combining with velocity-stress hybrid finite element formulation, the applicability of PML boundary is investigated and the numerical reflection of PML boundary is estimated. The reflectivity of PML and multi-transmitting formula (MTF) boundary is then compared based on body wave and surface wave simulations. The results show that although PML boundary yields some reflection, its absorption performance is superior to MTF boundary in the numerical simulations of near-fault wave propagation, especially in comer and large angle grazing incidence situations. The PML boundary does not arise any unstable phenomenon and the stability of PML boundary is better than MTF boundary in hybrid finite element method. For a specified problem and analysis tolerance, the computational efficiency of PML boundary is only a little lower than MTF boundary. 展开更多
关键词 perfectly matched layer multi-transmitting formula elastodynamic wave artificial boundary hybrid finite element
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Analysis of high-frequency local coupling instability induced by multi- transmitting formula - P-SV wave simulation in a 2D waveguide 被引量:6
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作者 Xie Zhinan Zhang Xubin 《Earthquake Engineering and Engineering Vibration》 SCIE EI CSCD 2017年第1期1-10,共10页
Local coupling instability will occur when the numerical scheme of absorbing boundary condition and that of the field wave equation allow energies to spontaneously enter into the computational domain. That is, the two... Local coupling instability will occur when the numerical scheme of absorbing boundary condition and that of the field wave equation allow energies to spontaneously enter into the computational domain. That is, the two schemes support common wave solutions with group velocity pointed into the computation domain. The key to eliminate local coupling instability is to avoid such wave solutions. For lumped-mass finite element simulation of P-SV wave motion in a 2D waveguide, an approach for stable implementation of high order multi-transmitting formula is provided. With a uniform rectangular mesh, it is proven and validated that high-freqaency local coupling instability can be eliminated by setting the ratio of the element size equal to or greater than x/2 times the ratio of the P wave velocity to the S wave velocity. These results can be valuable for dealing instability problems induced by other absorbing boundary conditions. 展开更多
关键词 absorbing boundary condition local coupling instability dispersion analysis group velocity multi-transmitting formula
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基于信息理论的航天相机性能评价研究 被引量:9
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作者 陈荣利 樊学武 李英才 《光学技术》 CAS CSCD 2004年第4期434-436,共3页
基于Shannon公式,提出了一种综合评价航天相机性能的新判据。给出了用系统的调制传递函数(MTF)与信噪比(SNR)的乘积大于或等于9来综合评价航天相机性能的方法。该方法为航天高分辨率相机的研制提供了参考。由于这个结论没有针对具体的相... 基于Shannon公式,提出了一种综合评价航天相机性能的新判据。给出了用系统的调制传递函数(MTF)与信噪比(SNR)的乘积大于或等于9来综合评价航天相机性能的方法。该方法为航天高分辨率相机的研制提供了参考。由于这个结论没有针对具体的相机,因而具有普遍的意义。 展开更多
关键词 航天相机 香农公式 系统的mtf
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常数分布Rankine源法与二阶绕射问题精度研究 被引量:7
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作者 徐刚 段文洋 《哈尔滨工程大学学报》 EI CAS CSCD 北大核心 2010年第9期1144-1152,共9页
为了准确地预报作用在浮体上的非线性水动力,采用时域二阶理论对非线性波物相互作用问题进行了研究.对自由面条件和物面条件进行Taylor级数展开和Stokes摄动展开得到一阶和二阶边值问题.使用基于Rankine源的边界元法计算每一时刻的流场... 为了准确地预报作用在浮体上的非线性水动力,采用时域二阶理论对非线性波物相互作用问题进行了研究.对自由面条件和物面条件进行Taylor级数展开和Stokes摄动展开得到一阶和二阶边值问题.使用基于Rankine源的边界元法计算每一时刻的流场,并在自由面上采用积分格式的自由面条件(IFBC);在远方控制面上采用多次透射边界条件(MTF).以圆球绕流和直立圆柱桩的二阶绕射问题为例,研究了所述方法的数值精度,经过对数值结果的比较与分析,得出了该方法精度较低的原因,并且得到MTF和IFBC可以有效地用于时域二阶问题的数值模拟,在远方人工边界上达到无反射的效果. 展开更多
关键词 二阶水动力 人工边界条件 积分格式 多次透射公式 积分格式自由面条件
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透射边界条件在波动谱元模拟中的实现:二维波动 被引量:10
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作者 邢浩洁 李鸿晶 《力学学报》 EI CSCD 北大核心 2017年第4期894-906,共13页
将邢浩洁和李鸿晶提出的多次透射公式(multi-transmitting formula,MTF)的谱元格式应用于均匀介质中线弹性SH波动问题的谱元模拟.假定紧邻人工边界的一层谱单元为具有直线边界的四边形单元,以保证每个人工边界节点都唯一对应一条指向内... 将邢浩洁和李鸿晶提出的多次透射公式(multi-transmitting formula,MTF)的谱元格式应用于均匀介质中线弹性SH波动问题的谱元模拟.假定紧邻人工边界的一层谱单元为具有直线边界的四边形单元,以保证每个人工边界节点都唯一对应一条指向内域的离散网格线.人工边界节点在某时刻的位移由该离散网格线上的节点在前若干时刻的位移确定,按照MTF谱元格式进行计算.通过平面波以一定角度传播的外源问题算例和点源脉冲自由扩散的内源问题算例,验证了方法的可行性以及对实际复杂波动问题的适用性.通过不同类型初值问题算例,在时域内分析了插值多项式阶次、人工波速和透射阶次三个参数对反射误差的影响.结果表明:插值多项式阶次较高的格式会表现出更好的精度,但总体上对反射误差的影响较小;人工波速对反射误差具有显著影响,当人工波速小于介质物理波速时反射误差较大,而当人工波速等于或稍大于介质物理波速时反射误差处于较低水平;透射阶次对反射误差具有决定性影响,表现在不失稳的情形下提高透射阶次能够迅速降低反射误差,但内源问题从三阶MTF开始出现飘移失稳,外源问题从二阶MTF开始出现轻微的飘移失稳. 展开更多
关键词 多次透射公式 谱元法 SH波动 mtf谱元格式 飘移失稳
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透射边界结合隐式有限元方法的计算精度探讨
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作者 倪同健 丁海平 +1 位作者 于彦彦 陈姚杰 《苏州科技大学学报(工程技术版)》 CAS 2020年第4期1-6,共6页
详细推导了采用隐式有限元与MTF结合进行地震作用下结构-地基系统的动力反应数值模拟方法,并选取了3种地形的二维场地模型,进行了地震波作用下的场地响应模拟。通过对比不同网格划分的数值模拟结果与精确解的差异,得到如下结果:对于有... 详细推导了采用隐式有限元与MTF结合进行地震作用下结构-地基系统的动力反应数值模拟方法,并选取了3种地形的二维场地模型,进行了地震波作用下的场地响应模拟。通过对比不同网格划分的数值模拟结果与精确解的差异,得到如下结果:对于有限元分析常采用的每个波长λ取10个单元的情况,一般可以得到较好的计算精度,但提高λ/Δx的数目,可以提高数值模拟的精度;时间步距Δt的减小对精度同样有所改善,只是较之空间步长而言,时间步距的改变对于精度的影响没有那么明显;对于复杂地形,建议取λ/Δx=20,并采用二阶MTF,这样可以大大地提高地震作用下场地响应的数值模拟精度。 展开更多
关键词 隐式有限元 多次透射公式mtf 网格划分 地震响应 数值模拟精度
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Normal transmitting boundary conditions 被引量:3
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作者 廖振鹏 《Science China(Technological Sciences)》 SCIE EI CAS 1996年第3期244-254,共11页
The multi-transmitting formula (MTF) governed by a single artificial speed is analytically developed into a generalized MTF governed by a few artificial speeds to improve its capacity in simultaneous simulation of sev... The multi-transmitting formula (MTF) governed by a single artificial speed is analytically developed into a generalized MTF governed by a few artificial speeds to improve its capacity in simultaneous simulation of several one-way waves propagating at different speeds.The generalized MTF is then discretized and further generalized using the space extrapolation to improve its accuracies in numerical simulation of transient waves at large angles of incidence.The above two successive generalizitions of MTF based on the notion of normal transmission lead to a compact formula of local non-reflecting boundary condition.The formula not only provides a general representation of the major schemes of existing local boundary conditions but can be used to generate new schemes,which combine advantages of different schemes. 展开更多
关键词 one-way WAVE motion non-reflecting BOUNDARY CONDITION multi-transmitting formula.
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Transmitting boundary and radiation conditions at infinity 被引量:7
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作者 廖振鹏 《Science China(Technological Sciences)》 SCIE EI CAS 2001年第2期177-186,共10页
Relationship between the radiation conditions at infinity and the transmitting boundary for numerical simulation of the near-field wave motion has been studied in this paper. The conclusion is that the transmitting bo... Relationship between the radiation conditions at infinity and the transmitting boundary for numerical simulation of the near-field wave motion has been studied in this paper. The conclusion is that the transmitting boundary is approximately equivalent to the radiation conditions at infinity for a large class of infinite media. And the errors of the approximation are of the same order of magnitude as those of the finite elements or finite differences in numerical simulation of wave motion. This result provides a sound theoretical basis for the transmitting boundary used in the numerical simulation of the near-field wave motion and gives a complete explanation for the major experiences accumulated in applications of the transmitting boundary to the numerical simulation. 展开更多
关键词 numerical simulation of wave motion radiation conditions at infinity local artificial boundary condition multi-transmitting formula
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