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排序方式: 共有109条查询结果,搜索用时 15 毫秒
1.
In this paper, we apply Homotopy Perturbation Method (HPM) to find the analytical solutions of nonlinear MHD flow of an incompressible viscous fluid through convergent or divergent channels in presence of a high magnetic field. The flow of an incompressible electrically conducting viscous fluid in convergent or divergent channels under the influence of an externally applied homogeneous magnetic field is studied both analytically and numerically. The graphs are presented to reveal the physical characteristics of flow by changing angles of the channel, Hartmann and Reynolds numbers.  相似文献   
2.
在哈特曼波前测量过程中,需要对哈特曼图像进行网格划分用于计算波前斜率。传统的网格划分方法通过观察哈特曼图像手动调整网格位置和网格间距。该方法不但需要人工干预,还给波前实时测量带来困难。为实现哈特曼图像网格划分的自动化,研究了基于相关法的哈特曼图像网格自动划分方法。该方法首先对哈特曼图像进行自相关求取网格行列数以及网格间距,然后利用该网格建立相应的模拟光斑图像,最后对模拟光斑图像和哈特曼图像进行互相关求取网格最佳位置。该方法无需人工干预,耗时短,实现了网格实时自动划分。  相似文献   
3.
建立哈特曼传感器的模型,证明在高空间分辨力下,可以采用Hudgin模型进行波面重构,避免了采用Fried模型带来的复杂性。对哈特曼子孔径缺失破坏连续性的问题进行了分析,介绍了相应的边缘处理算法。完成了基于离散傅里叶变换的波面重构算法数值模拟,实现了波面的无损重构。针对实际应用中输入波面在被遮挡处不连续的问题,提出了基于最小二乘解的拼接方案,实现了非连续波面拼接。分析了影响波面重构速度的主要因素,提出了提高波面重构性能的方法。  相似文献   
4.
The article is devoted to extension of boundary element method (BEM) for solving coupled equations in velocity and induced magnetic field for time dependent magnetohydrodynamic (MHD) flows through a rectangular pipe. The BEM is equipped with finite difference approach to solve MHD problem at high Hartmann numbers up to 106. In fact, the finite difference approach is used to approximate partial derivatives of unknown functions at boundary points respect to outward normal vector. It yields a numerical method with no singular boundary integrals. Besides, a new approach is suggested in this article where transforms 2D singular BEM's integrals to 1D nonsingular ones. The new approach reduces computational cost, significantly. Note that the stability of the numerical scheme is proved mathematically when computational domain is discretized uniformly and Hartmann number is 40 times bigger than length of boundary elements. Numerical examples show behavior of velocity and induced magnetic field across the sections.  相似文献   
5.
This work considers an electrically conducting fluid filled between two concentric cylindrical walls relatively close to each other. A theoretical solution for the steady Taylor–Couette flow between these two electrically insulated rotating cylinders under the influence of a radial magnetic field is provided in this work. By solving the appropriate set of governing equations simultaneously, the profiles of fluid tangential velocity component and induced magnetic field were obtained as complicated functions involving the modified Bessel functions of the first and second kinds of the first-order in terms of radial coordinates and Hartmann number. A computational study was also performed to validate the present theoretical solution. The analytical and computational results are identical when Ha = 1 while these results only slightly deviate from each other as Ha increases. Current results show that, the presence of the external magnetic field causes the flow close to the slower cylinder to accelerate while that close to the faster cylinder to decelerate. This has clearly implied the fact that an external magnetic field tends to make the velocity distribution across the inner and outer cylinders more uniform.  相似文献   
6.
在使用角锥棱镜前对其进行检测,选取误差较小的棱镜是一项关系到整个测量工作结果的重要任务。因此,提出一种用哈特曼波前传感器全面检测角锥棱镜角度误差和面形误差的技术方案,从理论上分析了哈特曼法的测量原理,深入研究了光经过角锥棱镜后的波面重建,给出了波面特征与角锥棱镜误差参量之间的关系。在试验中验证了这种方法的正确性和可行性。  相似文献   
7.
In this paper, the basic equations of two-phase liquid metal flow in a magnetic field are derived, and specifically, two-phase liquid metal MHD flow in a rectangular channel is studied, and the expressions of velocity distribution of liquid and gas phases and the ratioK 0 of the pressure drop in two-phase MHD flow to that in single-phase are derived. Results of calculation show that the ratioK 0 is smaller than unity and decreases with increasing void fraction and Hartmann number because the effective electrical conductivity in the two-phase case decreases. The Project is supported by the National Natural Science Foundation of China.  相似文献   
8.
在标量势和矢量势相等的条件下,严格求解了在广义非对称Hartmann势场中粒子运动的Klein Gordon方程;并利用束缚态边界条件,获得了束缚态能谱表达式和由超几何函数表示出的波函数.  相似文献   
9.
The flow of an electrically conducting incompressible viscous fluid in a plane channel with smooth expansion in the presence of a uniform transverse magnetic field has been analysed. A solution technique for the governing magnetohydrodynamic equations in primitive variable formulation has been developed. A co‐ordinate transformation has been employed to map the infinite irregular domain into a finite regular computational domain. The governing equations are discretized using finite‐difference approximations in staggered grid. Pressure Poisson equation and pressure correction formulae are derived and solved numerically. It is found that with increase in the magnetic field, the size of the flow separation zone diminishes and for sufficiently large magnetic field, the separation zone disappears completely. The peak u‐velocity decreases with increase in the magnetic field. It is also found that the asymmetric flow in a symmetric geometry, which occurs at moderate Reynolds numbers, becomes symmetric with sufficient increase in the transverse magnetic field. Thus, a transverse magnetic field of suitable strength has a stabilizing effect in controlling flow separation, as also in delaying the transition to turbulence. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   
10.
自适应光学中扩展信标波前探测的研究与实验   总被引:3,自引:0,他引:3  
陈珂  赵达尊 《光学技术》2001,27(5):387-390
讨论了一种基于Hartmann Shack (H S)传感器的扩展信标相关波前探测方法。通过在传统H S探测光路的物平面上加入视场光阑消除了子孔径像斑的重叠问题 ,并利用一种快速相关算法计算各像斑的相对位移 ,进而得到各子孔径波前的相对斜率。光学实验研究证实了该相关波前探测方法能够较精确地测算出波前像差 ,从而使目前使用最多的H S传感器具有扩展信标波前探测能力  相似文献   
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