共查询到20条相似文献,搜索用时 109 毫秒
1.
黎航 杨冬 李三伟 况龙钰 李丽灵 袁铮 张海鹰 于瑞珍 杨志文 陈韬 曹柱荣 蒲昱东 缪文勇 王峰 杨家敏 江少恩 丁永坤 胡广月 郑坚 《物理学报》2018,67(23):235201-235201
激光间接驱动惯性约束聚变实验中,黑腔内情况复杂,在激光烧蚀和辐射烧蚀等的驱动下,光斑区、冕区、纯辐射烧蚀区、射流区的多种等离子体以不同规律运动.发展了X光双能段窄能带的时间分辨成像方法,用以观测黑腔内多种等离子体的运动情况.在真空黑腔中观测到清晰的射流,分析了射流产生机制及其速度;在黑腔中充气,能有效消除射流和抑制冕区等离子体运动,但两种物质界面处可能会出现流体力学不稳定性等现象,分析了界面处的压力平衡关系和密度陡变情况. 相似文献
2.
三维激光烧蚀瑞利-泰勒不稳定性并行计算 总被引:3,自引:0,他引:3
给出了用三维激光烧蚀不稳定性程序求解的物理方程组,简要介绍了所用的数值方法.根据所模拟问题的物理性质和数值模拟方法探索了在多处理机上实行并行计算的技术和方法,并行效率达75%,在此基础上进行了三维多模激光烧蚀不稳定性的数值模拟,深化了对有关物理规律的认识. 相似文献
3.
直接驱动惯性约束聚变中,高温烧蚀初始印记在压缩过程的不稳定性发展中起着重要作用.利用X射线针孔辅助点投影成像法,研究了不同波形激光脉冲驱动下CH平面靶及其瑞利-泰勒不稳定性发展的情况.结果表明,在相同驱动激光能量作用下,初始阶段激光强度越低,上升越缓慢,高温烧蚀初始印记引起的密度调制幅度越大.提高预脉冲强度能显著抑制高温烧蚀初始印记效应.
关键词:
高温烧蚀初始印记
激光脉冲形状
瑞利-泰勒不稳定性
针孔辅助点投影 相似文献
4.
激光和辐射烧蚀引起的Rayleigh-Taylor(R-T)不稳定性是激光聚变的重要研究课题,本文讨论了R-T不稳定性实验的有关要求,在考虑烧蚀致稳的情况下,对特定的塑料薄膜靶用解析公式计算了R-T不稳定性线性发展阶段的积分增长指数随扰动波长、驱动源强度和持续时间的变化。给出某些感兴趣的物理图象,提供的信息可供有关实验和靶设计参考。 相似文献
5.
烧蚀引起R-T不稳定性实验条件的初步研究 总被引:2,自引:2,他引:0
激光和辐射烧蚀引起的Rayleigh-Taylor(R-T)不稳定性是激光聚变的重要研究课题,本文讨论了R-T不稳定性实验的有关要求,在考虑烧蚀致稳的情况下,对特定的塑料薄膜靶用解析公式计算了R-T不稳定性线性发展阶段的积分增长指数随扰动波长、驱动源强度和持续时间的变化。给出某些感兴趣的物理图象,提供的信息可供有关实验和靶设计参考。 相似文献
6.
使用LARED-S程序,参照NIF直接驱动DT点火靶,模拟研究了激光非均匀性对高收缩比球内爆内界面变形的影响。2维数值模拟计算表明:直接驱动高收缩比内爆对驱动激光非均匀性非常敏感,内界面流体不稳定性的发展严重破坏靶丸的对称压缩,使中心热斑的体积显著减小。以最大压缩时扰动增长幅度不超过热斑半径的1/3为限,模拟给出不同模数的低阶扰动模(模数小于等于12)对驱动激光均匀性的要求在2.5%~0.25%之间,其中模数在8~10之间的扰动模对激光功率均匀性的要求最严格,约为0.25%。 相似文献
7.
为研究激光烧蚀靶产生冲量过程和机理, 建立了一个复杂的一维热传导和流体动力学模型. 以空间碎片常见材料Al为例, 用建立的模型数值计算了纳秒脉宽激光烧蚀靶产生的冲量及冲量耦合系数随时间变化情况. 数值结果和已有的实验数据符合的较好. 数值计算表明: 激光脉冲时间内, 靶获得的冲量随时间迅速增加, 在脉冲时间结束后, 冲量变化随时间趋于稳定; 在冲量耦合过程中, 烧蚀等离子体向真空膨胀, 羽流尺度逐渐增大, 同时吸收入射激光能量, 导致激光与靶耦合的能量降低.
关键词:
激光烧蚀
冲量耦合
等离子体 相似文献
8.
激光烧蚀瑞利-泰勒不稳定性模拟 总被引:9,自引:5,他引:4
给出了激光烧蚀流体不稳定性计算程序EUL2D的物理方程,介绍了计算中使用的活动网格和一些技术问题处理。EUL2D程序的计算结果与Takabe公式、FAST2D程序和LASNEX程序的结果较好符合。数值计算日本大阪大学激光烧蚀瑞利-泰勒不稳定性实验,再现了实验结果。发现了横向电子热传导烧蚀在长波长扰动的非线性瑞利-泰勒不稳定性演变中起重要作用。 相似文献
9.
给出脉冲激光作用块状靶材的烧蚀模型.根据能量平衡原理,导出烧蚀面的位置随时间的变化关系.利用绝热近似、温度连续性条件和能量平衡原理来获得烧蚀面与固液相界面边界条件.结合热传导方程,利用精确解与积分近似法相结合的方案,给出固液两相的温度分布与时间和位置的变化关系,以及固液相界面的位置随时间的变化规律,并与已有的理论和实验结果进行比较.最后以铝靶为例计算模拟了激光烧蚀的全过程计算.
关键词:
脉冲激光
等离子体
固液相界面
烧蚀面 相似文献
10.
为了探索纳秒脉冲强激光与材料的相互作用机理,建立了二维数值模型,利用有限差分法对纳秒激光脉冲烧蚀金属铝的温度场进行了数值模拟.通过对比不同脉宽、光斑和能量下激光引起的温度场随时间的演化,发现脉冲的前期温度升高比后期快.等温图显示中心温度升高最快,烧蚀轮廓与激光束形状相似,烧蚀深度达1—5 μm.脉宽越长,烧蚀越窄和越深,光斑越大,烧蚀越宽和越浅.数值研究表明,1)激光的脉冲形状、脉宽和功率密度直接影响烧蚀的形状和深度,2)激光功率密度在109 W/cm2量级烧蚀 相似文献
11.
12.
流体界面不稳定性数值模拟中不同介质界面的处理方法 总被引:2,自引:0,他引:2
在界面不稳定性数值模拟中,以往的方法^〔1,4-8〕局限于密度不同的单种介质或绝热指数相同的两种介质问题,在计算绝热指数不同介质间的扰动时,界面上强制加入接触间断边界条件,从而避免了界面上数的非物理振荡,用三维程序TVD/AC对两种不同介质,在单波扰动下Rayleigh-Taylor不稳定性的发展进行了计算,得到了扰动随时间发展的图像。 相似文献
13.
14.
Xia Ma Paul T. GiguereBalaji Jayaraman Duan Z. Zhang 《Journal of computational physics》2010,229(20):7819-7833
When using the time explicit material point method to simulate interaction of materials accompanied by large deformations and fragmentation, one often encounters a numerical instability caused by small node mass, because acceleration on a mesh node is obtained by dividing the total force on the node by the mass of the node. When the material points are in the far sides of the cells containing the node, typically happening near material interfaces, the node mass can be very small leading to artificially large acceleration and then numerical instability. For the case of small material deformations, this instability is typically avoided by placing the material points away from cell boundaries. For cases with large deformations, with the exception of initial conditions, there is no control on locations of the material points. The instability caused by small mass nodes is often encountered. To avoid this instability tiny time steps are usually required in a numerical calculation. 相似文献
15.
16.
The interfacial RT instability experiments on imploding jelly liners in cylindrically convergent geometry have been performed. The liner‘s instability growth was observed clearly with a high-speed framing camera. Jelly liners have different initial perturbation forms on their inner and outer interfaces, being either smooth or sinusoidal. The initial perturbations also have different magnitudes and spatial frequencies (for example, mode n=-5, 10, 20). The experimental results show that the growth and coupling of perturbations on inner and outer surfaces are remarkably different. Meanwhile, the relevant 2-D numerical simulation of hydrodynamics combined with Level Set method has been performed. Using the numerical code, we can design the parameters of imploding jelly liner, and predict the experimental results. The results of simulation are demonstrated to be in good agreement with the measured data in a series of experiments. 相似文献
17.
本文基于磁流体动力学方程组,在保证磁场散度为零的条件下,采用CTU+CT(corner transport upwind+constrained transport)算法,对有无磁场控制下激波与重质或轻质三角形气柱相互作用过程进行数值研究.结果表明:无论有无磁场,两气柱在激波冲击下均具有完全不同的波系结构和射流现象.其中,入射激波与重气柱发生常规折射,形成介质射流,而与轻气柱作用则发生非常规折射,形成反相空气射流.无磁场时,气柱在激波冲击下,产生Richtmyer-Meshkov和Kelvin-Helmholtz不稳定性,界面出现次级涡序列,重气柱上下角卷起形成主涡对,轻气柱空气射流穿过下游界面后形成偶极子涡.施加横向磁场后,次级涡序列、主涡对以及偶极子涡均消失.进一步研究表明,在磁场作用下,洛伦兹力将不稳定性诱导产生的涡量向界面两侧的Alfvén波上输运,减少界面涡量沉积,抑制界面卷起失稳.最终,涡量沿界面两侧形成相互远离的涡层,界面不稳定性得到控制.此外,定量分析表明磁场能加快两气柱上游界面的运动,抑制下游界面的运动,且对轻气柱的控制效果更好. 相似文献
18.
Based on the numerical methods of volume of fluid (VOF) and piecewise parabolic method (PPM) and parallel circumstance of
Message Passing Interface (MPI), a parallel multi-viscosity-fluid hydrodynamic code MVPPM (Multi-Viscosity-Fluid Piecewise
Parabolic Method) is developed and performed to study the hydrodynamic instability and flow mixing. Firstly, the MVPPM code
is verified and validated by simulating three instability cases: The first one is a Riemann problem of viscous flow on the
shock tube; the second one is the hydrodynamic instability and mixing of gaseous flows under re-shocks; the third one is a
half height experiment of interfacial instability, which is conducted on the AWE’s shock tube. By comparing the numerical
results with experimental data, good agreement is achieved. Then the MVPPM code is applied to simulate the two cases of the
interfacial instabilities of jelly models accelerated by explosion products of a gaseous explosive mixture (GEM), which are
adopted in our experiments. The first is implosive dynamic interfacial instability of cylindrical symmetry and mixing. The
evolving process of inner and outer interfaces, and the late distribution of mixing mass caused by Rayleigh-Taylor (RT) instability
in the center of different radius are given. The second is jelly layer experiment which is initialized with one periodic perturbation
with different amplitude and wave length. It reveals the complex processes of evolution of interface, and presents the displacement
of front face of jelly layer, bubble head and top of spike relative to initial equilibrium position vs. time. The numerical
results are in excellent agreement with that experimental images, and show that the amplitude of initial perturbations affects
the evolvement of fluid mixing zone (FMZ) growth rate extremely, especially at late times. 相似文献
19.
Ravi Samtaney 《Journal of computational physics》2009,228(18):6773-6783
We present a numerical method to solve the linear stability of impulsively accelerated density interfaces in two dimensions such as those arising in the Richtmyer–Meshkov instability. The method uses an Eulerian approach, and is based on an upwind method to compute the temporally evolving base state and a flux vector splitting method for the perturbations. The method is applicable to either gas dynamics or magnetohydrodynamics. Numerical examples are presented for cases in which a hydrodynamic shock interacts with a single or double density interface, and a doubly shocked single density interface. Convergence tests show that the method is spatially second-order accurate for smooth flows, and between first and second-order accurate for flows with shocks. 相似文献
20.
Dynamics of multiphase flow under high voltage has attracted extensive research interests due to its wide industrial applications. In this paper, numerical solution of electro-hydrodynamic behavior and interface instability of double emulsion droplet is presented. Level set method and leaky dielectric model coupled with Navier-Stokes equation are used to solve the electro-hydrodynamic problem. The method is validated against the theoretical analysis and the simulation results of the other researchers. Double emulsion droplet with inner droplet (core) and outer droplet (shell) phases immersed in continuous phase is subjected to high electric field. Shell/continuous and core/shell interfaces of the droplet undergo prolate-oblate or oblate-prolate deformation depending on the extent of the penetration of electric potential and sense of charge distribution at the interfaces. The deformation of the shell deviates from theory at larger volume fraction of core for oblate-prolate case whereas it follows theory for prolate-oblate case. The interfaces showing oblate-prolate deformation split at the poles whereas, for prolate-oblate, they split away along the equator. The re-union of the interfaces under high electric field results with production of daughter droplet at the core. The large decrease in critical electric field for oblate-prolate case shows their less interface stability at larger volume fraction of core. When the core is eccentric, the electric field drives it towards the shell center or to the shell/continuous interface depending on electrical parameters. The study is beneficial in understanding the electro-hydrodynamic behavior of emulsion droplets and efficient design of related industrial processes. 相似文献