Two-dimensional simulation of pellet ablation with atomic processes
Two-dimensional simulation of pellet ablation with atomic processes
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DOI：
10.1063/1.1769376
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发表时间：
2004-07
影响因子：
2.2
通讯作者：
R. Ishizaki;P. Parks;N. Nakajima;M. Okamoto
中科院分区：
文献类型：
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作者：
R. Ishizaki;P. Parks;N. Nakajima;M. Okamoto
开发了一个二维流体动力学模拟程序CAP，用于研究磁化等离子体中氢化弹丸烧蚀的整个时间演化过程。该程序的一个特点是，它处理颗粒表面的固-气相变，而不像以前的烧蚀模型那样在那里施加人工边界条件。数值模拟包括多组分原子过程，主要是烧蚀过程中的分子解离和热电离，采用动力学热流模型。研究发现，电离导致在烧蚀流的超音速区域形成准静态激波锋面，然后是更远的“第二”声速表面。由于磁场的方向性，各向异性加热导致颗粒表面的烧蚀(反冲)压力分布不均匀。由于在足够高的热流密度下，剪切应力可以超过固体的屈服强度，所以当固体颗粒烧蚀和失重时，固体颗粒可以被流态化并压扁成“煎饼”形状。在烧蚀过程中，弹丸变形可以使弹丸寿命缩短近3倍，而弹丸在烧蚀过程中保持刚性和静止。
A two-dimensional hydrodynamic simulation code CAP has been developed in order to investigate the dynamics of hydrogenic pellet ablation in magnetized plasmas throughout their temporal evolution. One of the properties of the code is that it treats the solid-to-gas phase change at the pellet surface without imposing artificial boundary conditions there, as done in previous ablation models. The simulation includes multispecies atomic processes, mainly molecular dissociation and thermal ionization in the ablation flow beyond the pellet, with a kinetic heat flux model. It was found that ionization causes the formation of a quasistationary shock front in the supersonic region of the ablation flow, followed by a “second” sonic surface farther out. Anisotropic heating, due to the directionality of the magnetic field, contributes to a nonuniform ablation (recoil) pressure distribution over the pellet surface. Since the shear stress can exceed the yield strength of the solid for a sufficiently high heat flux, the solid pellet can be fluidized and flattened into a “pancake” shape while the pellet is ablating and losing mass. The effect of pellet deformation can shorten the pellet lifetime almost 3× from that assuming the pellet remains rigid and stationary during ablation.