结构对太赫兹超材料光调控特性的影响

利用光泵浦太赫兹探测系统研究了3个基于开口谐振环的超材料的光调制性质。结果表明:当太赫兹波的电场矢量平行于超材料底边，设计太赫兹超材料时，需要避免对称性样品的中间条等长。然而，非对称性的样品存在耦合和劈裂现象。由于不同的共振机制，低频LC共振对光较为敏感。虽然样品由于设计结构的区别使得各自共振峰位有所不同，但它们对光所呈现出的调制特性是相同的。即当太赫兹波的电场矢量平行于超材料两侧的边时，由于结构的原因在透射谱中只有一个透射凹陷，此透射凹陷表现为偶极共振且该偶极共振特性对光激励不敏感。

Numerical calculation of turbulent convection heat transfer over infrared dome based on SST turbulence model

Spherical dome usually works in the state of turbulent convection heat transfer for the penetration infrared guidance system flying at low altitude and high speed. In this paper, the sphere-cone at zero attack corner was focused on. Numerical calculation engineering method of turbulent convection heat transfer for dome was proposed by using SST model, which was implemented by generating the structure grid, setting physical property parameter of inflow and compared with the engineering formula of heat transfer at stagnation point and turbulent region. Firstly, based on Billig's results, detached shock was generated in flow field by use of multi-block structured grid in order to reduce the numerical dissipation. In order to analyze the sensitivity of the calculation results to near-wall grid, several numerical experiments were performed with grid of different near-wall node heights. Then, the influence of SST model parameters on the calculation results was analyzed and Bradshaw number only had an obvious impact on the computation of peak heat flux. The result of heat flux at stagnation point calculated by SST model was consistent with Klein's formula by using the correction approach of equivalent thermal conductivity for inflow. At the region of turbulent flow over dome, the Bradshaw number was modified by applying the engineering formula of turbulent heat transfer over the sphere at high speed. The result of heat flux computed by SST model was consistent with this engineering formula. The results calculated by modified SST model could satisfy the requirement of engineering applications and could be applied to analyze thermal shock resistance of dome, aero-optic effects, non-uniformity correction of infrared images and trajectory design of terminal guidance for infrared or laser guidance system. This numerical calculation method plays an important role in engineering design of optical guidance system at high speed.