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为研究高能脉冲激光烧蚀铝靶材瞬态流动过程和形成的羽流流场能量转化过程,采用阴影法对纳秒激光烧蚀铝靶羽流膨胀及演化过程进行研究,得到烧蚀流场演化时序图;利用动量守恒方程,建立烧蚀羽流在环境气体中膨胀模型。由实验测量结果,通过对流场参数的无量纲化处理,分析得到烧蚀流场无量纲羽流动能、环境气体动能以及热能之间的能量转化过程。研究表明,初始时刻,由于烧蚀压要远大于环境气压,羽流膨胀与真空中的自由膨胀行为类似,此后,羽流动能逐渐转化为环境气体动能和热能;当无量纲激波半径为1时,羽流的无量纲动能等于被羽流推起的气体的动能,而热能约等于总能量的1/2,最终全部转化为羽流和环境气体热能。
In order to study the transient flow process and the energy conversion process of the plume formed by high energy pulsed laser ablation aluminum target, the shadowing method was used to study the plume expansion and evolution process of aluminum target ablated by nanosecond laser. The ablation flow field Evolution timing diagram; use of momentum conservation equation, the establishment of ablation plume expansion in the ambient gas model. From the experimental results, through the non-dimensional treatment of the flow field parameters, the energy conversion between the non-dimensional plume kinetic energy, ambient gas kinetic energy and thermal energy in the ablation flow field is analyzed. The results show that, at the initial time, the plume flow is gradually transformed into the kinetic and thermal energy of the ambient gas since the ablation pressure is much larger than the atmospheric pressure. The plume expansion is similar to the free expansion in the vacuum. When the dimensionless shock radius is 1 , The non-dimensional kinetic energy of the plume is equal to the kinetic energy of the gas pumped up by the plume, while the heat energy equals about 1/2 of the total energy and eventually all is converted into the plume and the thermal energy of the ambient gas.