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中国物理学会期刊

激波与轻质气柱作用过程的磁场抑制特性

CSTR: 32037.14.aps.73.20231916

Magnetic field suppression characteristics in interaction process between shock wave and light gas cylinder

CSTR: 32037.14.aps.73.20231916
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  • 本文采用CTU (corner transport upwind)+CT (constrained transport)算法求解理想可压缩磁流体动力学(magneto-hydro-dynamic, MHD)方程, 仿真研究了不同方向磁场控制下高斯分布轻质气柱界面受平面冲击波扰动后的演化过程, 揭示了磁场方向对界面不稳定性的影响机理. 仿真结果探讨了有/无磁场作用下流场特性与波系结构的发展, 对比分析了磁场方向对气柱的长度、高度、射流宽度和体积压缩率的影响, 并结合流场上半区环量、能量分量、速度和磁场力分布, 多角度分析了磁场方向对界面不稳定性的影响机理. 结果表明, 磁压力推动涡量远离界面, 降低了涡量在密度界面上的沉积而附着在分裂后的涡层上, 从而有效抑制Richtmyer-Meshkov不稳定性对界面的影响; 由于磁张力附着在被分离的涡层上, 且其作用方向与界面因速度剪切而卷起涡的方向相反, 因此抑制了界面因Kelvin-Helmholtz不稳定性而形成涡串. 另外, 纵向磁场控制下的磁张力反作用于中轴射流方向, 同样抑制了Rayleigh-Taylor 不稳定性的发展.

     

    Based on ideal compressible magnetohydrodynamics (MHD) equations, the interface instabilities induced by the interaction between planar shock wave and the light gas (Helium) cylinder under the influence of the magnetic fields with different directions are investigated numerically by using the CTU(corner transport upwind)+CT (constrained transport) algorithm. The numerical results elucidate the evolution of flow field characteristics and wave structures with and without magnetic field. Moreover, we examine the influence of the magnetic field direction on a characteristic scales (including the length, height and width of the central axis of gas cylinder), as well as the volume compressibility. Then, the mechanism of the magnetic field direction affecting the interface instability is studied in depth by integrating the analyses of the circulation, energy, velocity and magnetic force distribution within the flow field. The core of this study, is to explore the suppression mechanism of interface instability by magnetic field force. The results show that the magnetic pressure plays a crucial role in driving vorticity away from the interface, thereby reducing its deposition on the density interface. Simultaneously, it adheres to the divided vortex layer, thereby effectively isolating the influence of Richtmyer-Meshkov instability on the interface. On the other hand, the magnetic tension adheres to the separated vortex layer, and its direction is opposite to that of the vorticity generated by the shear of interface velocity. This action effectively suppresses the Kelvin-Helmholtz instability and the rolling-up of vortices on the density interface. Additionally, under the control of a longitudinal magnetic field, the direction of magnetic tension is opposite to the direction of the central jet, effectively suppressing the development of Rayleigh-Taylor instability.

     

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