Time-evolution characteristics of flash radiation of gasified aluminum in aluminum-aluminum hypervelocity impact
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摘要: 撞击闪光辐射现象是超高速撞击过程中的典型物理现象之一。针对撞击闪光辐射机制和演化规律开展研究，对建立不同尺度撞击闪光辐射特征相似性关系和光学探测分辨超高速撞击动力学过程具有重要意义。在铝–铝超高速撞击闪光辐射强度时间演化过程中，会产生一个持续十几微秒的闪光辐射，实验测量分析发现该辐射过程与气体冲击波辐射特征相似。基于辐射传输理论，模拟分析了Taylor模型辐射强度时间演化特征及其影响因素，对比分析了超高速撞击反溅碎片云中的气化铝闪光辐射强度演化信息。研究结果表明：超高速撞击闪光辐射中持续时间较长的辐射强度演化峰的峰值出现时刻与靶室压强负相关。Abstract: Flash radiation is one of the typical phenomena produced in hypervelocity impacts. The study of the radiation mechanisms and evolution law of the impact flash is important for building the similarity relationship between the different scales and probing the dynamics of the hypervelocity impact. In the low pressure atmosphere, the flash radiation mechanisms in aluminum-aluminum hypervelocity impacts are multiplex. One of the radiation processes standing for tens microsecond duration may result from the ablation of tiny fragments. Analysis of impact experiments shows that the characteristics of the processes are close to with the description of the Taylor point explosion model, but further study of the radiation distribution is still lacking. In this paper, the evolution characteristics of the impact flash produced in hypervelocity impact are discussed by considering the effect of the radiation transfer in the impact products. It is found that there exists a peak structure in the time evolution of the radiation intensity, which presents a proportional law showing that the position of the radiation peak depends on the energy and density of the wave shock. The proportional law can be used to establish the relation between the chamber pressure and the radiation peak time of the shock wave. In addition, this work puts forward an approximate solution of the radiation evolution, which is derived from the radiation transfer theory and shows agreement with the results detected by experiments. The consistent results indicate the tens-microsecond-standing peak appeared in the impact flash is generated by the expansion of the shock wave, and the radiation intensity depends mainly on the expansion area and the dynamical evolution of the states of the gas distributed in the shock wave. It provides a theoretical reference for the research of the evolution law and the phenomena of the hypervelocity impact flash.
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Key words:
- hypervelocity impact /
- impact flash /
- radiation transfer /
- radiation intensity /
- time-evolution /
- gasified aluminum
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图 1 铝–铝超高速碰撞反溅碎片云测量结果
Figure 1. The measurement result of the backward debris cloud for the aluminum-aluminum hypervelocity impact experiment
图 2 395 nm处撞击闪光辐射强度时间演化曲线
Figure 2. The time variation curve of the impact-flash radiation intensity at 395 nm, where the ordinate is normalized by the long radiation peak
图 3 Taylor模型冲击波压强、密度和温度分布曲线
Figure 3. The pressure, density and temperature as function of the self-simulating variable ξ
图 4 Taylor模型冲击波在不同膨胀半径R下的辐射成像计算模拟结果
Figure 4. The simulation result of shock wave based on Taylor model with different R
图 5 辐射强度随冲击波膨胀半径R的变化
Figure 5. The radiation intensity as function of the shock wave radius R
图 6 辐射强度演化峰的峰值位置随密度和能量变化的曲线
Figure 6. The position of the radiation peak as function of the density and the energy
图 7 辐射强度演化峰的峰值位置随能量和密度的变化曲线
Figure 7. The position of the radiation peak versus the energy and the density
图 8 辐射强度演化峰的峰值位置随η变化的曲线
Figure 8. The curves of the position Rp of the radiation peak versus η
图 9 辐射强度随时间演化信号
Figure 9. The time evolution results of the radiation intensity signals
表 1 铝原子气体相关原子光谱结构参数
Table 1. The atomic spectra lines data of Al
编号 λ/mm Aij /（107 s−1） gi gj 1 394.40 4.98 2 2 2 396.15 9.82 2 4 
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表 2 实验参数及峰值时刻
Table 2. The experimental parameters and the peak time
实验编号 撞击速度/（km·s−1） 靶室压强pc/Pa 峰值时刻tp/μs 1 6.119 4 4.669 2 6.132 32 2.160 3 5.947 100 1.157
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