纳秒脉冲激光能量沉积激波减阻机理数值研究

Numerical study of shock wave drag reduction mechanism by nanosecond-pulse laser energy deposition

为详细揭示纳秒单脉冲激光能量沉积激波减小波阻的机理,分别研究了单脉冲激光能量沉积与正激波相互作用、单脉冲激光能量沉积与弓形激波超声速流场相互作用。鉴于常用数值模拟方法不考虑空气的离解和电离,不能合理模拟激光能量沉积诱导等离子体热核的空间分布,采用泪滴形能量分布,且耦合有限速率化学反应模型,所得到的激波和热核演化过程的数值模拟结果与实验吻合程度高,验证了所提出模拟方法的合理性。分别选取马赫数为1.92条件下的正激波和弓形激波,入射激光能量大小为10.1 mJ和12 mJ,研究表明:单脉冲激光能量沉积诱导形成的等离子体热核通过正激波后,形成上下对称的涡环结构;在弓形激波条件下,在波后形成的低压涡环引起波阻减小,这是激波减阻的主要机理。

To reveal the mechanism of shock wave drag reduction by single nanosecond-pulse laser energy deposition,the interactions between single laser energy deposition and normal shock wave,the single laser energy deposition and bow shock wave in supersonic flow field were studied numerically.Dissociation and ionization of air usually were not taken into consideration in typical simulation method,so appropriate space distribution of laser energy deposition induced plasma cannot be obtained.Tear-drop initial energy distribution and finite rate reaction model were adopted in this work.The simulation results of shock wave and hot core evolution processes are in good accordance with those of experiments,which verifies the rationality of the proposed simulation method.The normal shock and bow shock wave under the condition of Maher number 1.92 are selected respectively.The incident laser energy is 10.1 mJ and 12 mJ.Results show that the hot core of laser energy deposition induced plasma cloud turns into low pressure symmetrical vortex ring after the interaction with normal shock wave.In the condition of bow shock wave,the shock wave drag induced by low pressure vortex ring is reduced,which formed after the shock wave.It is the main mechanism of shock wave drag reduction.