共查询到20条相似文献,搜索用时 125 毫秒
1.
在移动最小二乘法的基础上,提出了复变量移动最小二乘法.复变量移动最小二乘法的优点是采用一维基函数建立二维问题的逼近函数,所形成的无网格方法计算量小.然后,将复变量移动最小二乘法应用于弹性力学的无网格方法,提出了复变量无网格方法,推导了复变量无网格方法的公式.与传统的无网格方法相比,复变量无网格方法具有计算量小、精度高的优点.最后给出了数值算例.
关键词:
移动最小二乘法
复变量移动最小二乘法
无网格方法
弹性力学
复变量无网格方法 相似文献
2.
结合无网格局部彼得洛夫-伽辽金(MLPG)方法和径向基函数有限差分(RBF-FD)无网格方法求解非线性热传导问题。MLPG方法属于弱式无网格方法,具有处理边界条件方便的优点,然而因其要做大量的插值、积分运算而计算效率偏低;RBF-FD无网格方法属于强式无网格方法,直接对微分算子进行数值离散,计算效率高,然而其边界条件的处理较复杂。将二者相结合,在求解域边界附近采用MLPG方法,其它区域采用RBF-FD无网格方法,则能扬长避短。介绍了MLPG方法和RBF-FD无网格方法的基本原理,将该混合方法用来求解非线性热传导方程,数值算例显示了方法的正确性和高效性。 相似文献
3.
4.
本文通过破开算子方法,把二维输运问题的控制方程破开为对流问题和扩散问题。在任意四边形网格的离散下,用特征线法解对流问题,并采用伽辽金加权余量法,从而有效地减少插值所引起的数值阻尼,提高计算精度。用有限单元法和迭代计算格式解扩散问题。由于采用了辛普生积分公式,在每个时间步长都不需要求逆矩律,节省了计算时间。算例表明,本文数值模拟结果与精确的理论解吻合较好。 相似文献
5.
6.
7.
将滑动Kriging插值法与无网格局部Petrov-Galerkin法相结合,采用Heaviside分段函数作为局部弱形式的权函数,提出改进的无网格局部Petrov-Galerkin法,进一步将这种无网格法应用于位势问题,并推导相应的离散方程.因为滑动Kriging插值法构造的形函数满足Kronecker函数性质,所以本文建立的改进的无网格局部Petrov-Galerkin法可以像有限元法一样直接施加边界条件;由于采用Heaviside分段函数作为局部弱形式的权函数,因此在计算刚度矩阵时只涉及边界积分,而没有区域积分.此外,还对本方法中一些重要参数的选取进行了研究.数值算例表明,本文建立的改进的无网格局部Petrov-Galerkin法具有数值实现简单、计算量小以及方便施加边界条件等优点. 相似文献
8.
将重构核粒子法(RKPM)和边界积分方程方法结合,提出了一种新的边界积分方程无网格方法——重构核粒子边界无单元法(RKP-BEFM).对弹性力学问题,推导了其重构核粒子边界无单元法的公式,研究其数值积分方案,建立了重构核粒子边界无单元法离散化边界积分方程,并推导了重构核粒子边界无单元法的内点位移和应力积分公式.重构核粒子法形成的形函数具有重构核函数的光滑性,且能再现多项式在插值点的精确值,所以本方法具有更高的精度.最后给出了数值算例,验证了本方法的有效性和正确性.
关键词:
重构核粒子法
弹性力学
边界无单元法 相似文献
9.
运用无网格流形方法求解动态断裂力学问题.该方法利用单位分解法和有限覆盖技术建立形函数,形函数的建立不受域内不连续的影响,可较好地求解裂纹问题.对于局部化问题,该方法的形函数构造较其他方法更为有效,避免了其他方法在建立试函数时没有考虑不连续尖端的缺点.由于采用有限覆盖技术建立试函数,该方法克服了不连续对试函数的影响,尤其当不连续变得复杂时,更能显示该方法在处理不连续方面的优点.在求解动态断裂力学问题时,弹性动力学积分弱形式的推导采用加权残数法,空间离散采用基于单位分解法的无网格流形方法,时间离散主要采用Newmark法.最后给出两个数值算例,将计算结果与解析解对比,说明该方法的正确性和可行性.
关键词:
有限覆盖
无网格流形方法
动态断裂力学
动态应力强度因子 相似文献
10.
11.
Electric field gradients (EFG) due to Cu, Zn and Ga impurities in silver were studied by the perturbed angular correlation
technique using the probe atom111In/111Cd. A large deviation from the axial symmetry was observed for the EFG at a nearest neighbour site to Zn and Ga impurities.
The molecular cluster method calculations can reproduce the magnitude of the EFG, however, does not account for the asymmetry
parameter. 相似文献
12.
Element-free Galerkin (EFG) method for a kind of two-dimensional linear hyperbolic equation 下载免费PDF全文
The present paper deals with the numerical solution of
a two-dimensional linear hyperbolic equation by using the element-free
Galerkin (EFG) method which is based on the moving least-square
approximation for the test and trial functions. A variational method
is used to obtain the discrete equations, and the essential boundary
conditions are enforced by the penalty method. Compared with
numerical methods based on mesh, the EFG method for hyperbolic
problems needs only the scattered nodes instead of meshing the
domain of the problem. It neither requires any element connectivity
nor suffers much degradation in accuracy when nodal arrangements are
very irregular. The effectiveness of the EFG method for two-dimensional
hyperbolic problems is investigated by two numerical examples in
this paper. 相似文献
13.
The present paper deals with the numerical solution of the
third-order nonlinear KdV equation using the element-free Galerkin
(EFG) method which is based on the moving least-squares approximation. A
variational method is used to obtain discrete equations, and the
essential boundary conditions are enforced by the penalty method.
Compared with numerical methods based on mesh, the EFG method for
KdV equations needs only scattered nodes instead of meshing the
domain of the problem. It does not require any element connectivity
and does not suffer much degradation in accuracy when nodal
arrangements are very irregular. The effectiveness of the EFG method
for the KdV equation is investigated by two numerical examples in this
paper. 相似文献
14.
The electric field gradient tensor (EFG) can be measured accurately by various experimental techniques. The theoretical understanding,
however, was restricted to point charge models, Sternheimer antishielding factors and model calculations for a restricted
number of compounds. We have developed a method which obtains the EFG from a full potential linearized augmented plane wave
(LAPW) energy band structure calculation. Starting from the total crystal charge density (including the core electrons) the
EFG is obtained numerically without further approximations. We have applied our method successfully to all hep metals up to
Cd, to semiconductors, and to insulators such as lithiumnitride or cuprite. Good agreement with experiment is found and we
predict interesting changes in the sign of the EFG in the 3d and 4d transition metal series. The aspherical distribution of
the valence electrons determines 80 or 90% of the total EFG and the influence of the core electrons is small. Even for the
3d and 4d metals the asphericity of the valence p electrons dominates over the d contribution to the EFG due to the different
radial behavior of p and d wave functions. 相似文献
15.
A class of experimental techniques known as hyperfine methods can be used to measure electric field gradients (EFGs) through the hyperfine interaction experienced by tracer nuclei. When EFGs fluctuate at rates comparable to the inverse characteristic timescale of the hyperfine method, there is a loss of signal coherence that can be used to determine EFG fluctuation rates. This has been used to measure, for example, EFG fluctuations accompanying atomic jumps of radiotracers using perturbed angular correlation spectroscopy (PAC). Nominally, there is a one-to-one correspondence between EFG fluctuation and tracer jump, but when tracer jumps are mediated by a vacancy diffusion mechanism, a subset of multiple tracer-vacancy exchanges will not affect spectra when they occur much faster than the hyperfine timescale, leading to an underestimate of underlying tracer jump rate if this correlated random-walk effect is not taken into consideration. The present work calculates the factor by which EFG fluctuation rate differs from tracer jump rate based on a time-dependent, random-walk analysis of tracer displacement probabilities in a vacancy encounter model for the special case of self-diffusion in the L12 crystal structure. 相似文献
16.
An improved element-free Galerkin method for solving generalized fifth-order Korteweg-de Vries equation 下载免费PDF全文
In this paper, an improved element-free Galerkin (IEFG) method is proposed to solve the generalized fifth-order Korteweg-de Vries (gfKdV) equation. When the traditional element-free Galerkin (EFG) method is used to solve such an equation, unstable or even wrong numerical solutions may be obtained due to the violation of the consistency conditions of the moving least-squares (MLS) shape functions. To solve this problem, the EFG method is improved by employing the improved moving least-squares (IMLS) approximation based on the shifted polynomial basis functions. The effectiveness of the IEFG method for the gfKdV equation is investigated by using some numerical examples. Meanwhile, the motion of single solitary wave and the interaction of two solitons are simulated using the IEFG method. 相似文献
17.
An improved element-free Galerkin method for solving the generalized fifth-order Korteweg–de Vries equation 下载免费PDF全文
In this paper, an improved element-free Galerkin (IEFG) method is proposed to solve the generalized fifth-order Korteweg-de Vries (gfKdV) equation. When the traditional element-free Galerkin (EFG) method is used to solve such an equation, unstable or even wrong numerical solutions may be obtained due to the violation of the consistency conditions of the moving least-squares (MLS) shape functions. To solve this problem, the EFG method is improved by employing the improved moving least-squares (IMLS) approximation based on the shifted polynomial basis functions. The effectiveness of the IEFG method for the gfKdV equation is investigated by using some numerical examples. Meanwhile, the motion of single solitary wave and the interaction of two solitons are simulated using the IEFG method. 相似文献
18.
An improved complex variable element-free Galerkin method for two-dimensional elasticity problems 下载免费PDF全文
In this paper, the improved complex variable moving least-squares (ICVMLS) approximation is presented. The ICVMLS approximation has an explicit physics meaning. Compared with the complex variable moving least-squares (CVMLS) approximations presented by Cheng and Ren, the ICVMLS approximation has a great computational precision and efficiency. Based on the element-free Galerkin (EFG) method and the ICVMLS approximation, the improved complex variable element-free Galerkin (ICVEFG) method is presented for two-dimensional elasticity problems, and the corresponding formulae are obtained. Compared with the conventional EFG method, the ICVEFG method has a great computational accuracy and efficiency. For the purpose of demonstration, three selected numerical examples are solved using the ICVEFG method. 相似文献
19.
K. Kovács E. Kuzmann Z. Homonnay A. Vértes L. Gunneriusson A. Sandström 《Hyperfine Interactions》2008,181(1-3):69-73
The structure around the metal site of mavicyanin, a protein molecule with a copper site, was investigated in solution by using time-differential perturbed angular correlation of 117In. The electric field gradient (EFG) of the metal site was deduced from the measurement. It demonstrated that the site in a mutant-type mavicyanin, Thr15Ala-Mav, gives an EFG different from that in the wild-type mavicyanin does. The pH dependence of the EFG was also observed for both proteins. 相似文献
20.
The variation of the electric field gradient (EFG) at nuclear sites with pressure in semimetallic arsenic and antimony has
been calculated using the full-potential linearized augmented plane wave (FLAPW) method. The results are compared with NQR
data, which are available up to a pressure of 2 GPa. The calculated EFG depends sensitively on the values of the lattice parameters
used. A theoretical investigation of the relationship between c/a and the internal parameter z, using FLAPW methods, has been carried out and compared with available X-ray diffraction data
for arsenic and antimony. For antimony, the FLAPW calculations give results which are consistent with the experimental pressure
variation of both the lattice parameters and the EFG. In the As case, the use of theoretical values of z leads to good agreement
with the measured pressure variation of the EFG.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献