弱电离高超声速流场对太赫兹波传播影响

在再入飞行过程中生成的等离子体鞘套对电磁波传播的影响引起了很多的关注。包覆飞行器的等离子体鞘套通常为一团弱电离的气体。等离子体鞘套的存在会影响飞行器与地面间的通信,甚至带来通讯黑障问题。为了解决这一问题,进行了大量的研究并提出提高电磁波频率可以成为一种解决方式。随着可以生成高强度太赫兹源的设备出现,电磁波与等离子体间相互作用在微波波段的研究局限被打破,高频率的太赫兹波与等离子体间的相互作用也引起了更多关注。通过计算流体力学方法对包覆飞行器的热力学和化学动力学非平衡流体进行数值计算可以得到包覆高超声速飞行器的流场分布, 以此可以得到等离子体鞘套的电磁特性。通过数值计算得到四种飞行场景下的等离子体鞘套,并分析了不同传播路径下太赫兹波与等离子体鞘套的相互作用,结果表明:当飞行高度较低,鞘套等离子体密度较大时,太赫兹波具有穿过等离子体鞘套的能力,可以为通讯黑障问题的解决提供理论支持。

Effects of weakly ionized hypersonic flow on propagation of terahertz wave

The plasma sheath produced in the progress of entry or reentry flight has attracted much attention as it would impact the propagation of electromagnetic wave. This plasma sheath is a group of weakly ionized gas in general and has the ability to influent the communication between aero craft and ground. Sometimes the existence of this plasma sheath even cloud cause the communication blackout which is not desirable. To improve this problem plenty of researches have done, some of the researches mentioned that raising the wave frequency could be one way. The development of intensive terahertz sources broke up the restrain of electromagnetic wave in microwave range, there comes out several researches on the interaction between terahertz wave and plasma. Computational fluid dynamics was used in numerical simulating of a thermodynamics and chemical nonequilibrium flow over the aero craft to calculate the electromagnetic characteristics of plasma layer. Four flight scenes and different incidence forms were taken to discuss the interaction between terahertz wave and plasma sheath. And the propagation of terahertz wave along with different paths was discussed. From the simulating results, terahertz wave is capable to transmit in the plasma sheath with high electron density when the flight height is lower.