**5. Conclusion**

This chapter concentrates on the numerical study of modeling aero-optical transmission and imaging through the supersonic flow fields. We have developed two computational models for predicting aero-optical performance of the supersonic flow fields, respectively, using geometrical optical method and information optical method. Firstly, this model combining the CFD model with the geometrical optics is discussed in detail. The calculation results are coincident favorably with prior knowledge from the completed research about aero-optics. The model has been compared with the experimental knowledge about the influences of the supersonic flow fields on optical transmission. Due to test complication and lack of experiment facilities, a complete comparison cannot be allowed. The model has merits not only in predicting optical performance of supersonic flow field but also in understanding the aero-optical characteristic of a particular design.

In addition, this chapter also provides a solution to aero-optical problems in terms of information optics. A computational model for studying aero-optical imaging through the supersonic flow fields is presented. This model integrates the CFD grids with the model of angular spectrum propagation to construct serially connected optical subsystems for representing the supersonic flow fields. The simulation results are qualitatively coincident with prior knowledge about aero-optical effects. The proposed model can be directly helpful in restoring the image degraded by the supersonic flow fields. Compared with the geometrical optical method, the provided approach based on the information optics can overcome the complexity of ray tracing, and give the explicit shifts of the image and describe the blur circle of the degraded image. However, the computational results are discussed qualitatively due to unavailability of the corresponding wind tune experiments. In future, more extensive computational experiments will be done so as to study the imaging under different field of view and do the comparisons under different premises.

The research methods in this chapter are also suitable for the other optical transmitting through the air turbulence and high-speed flow fields. If the issues discussed above can be take consideration into the passive aero-optical system, the other similar problems will be sure to be faced in the active optical systems. As we all know, in the near the future, airborne active laser emitter/laser communication systems will come true. There are optical beams emitting through the high-speed flow fields, and then, airborne lasers are adversely affected by this flow field when operating. In the active system, the flow field causes the projected beam energy to attenuate and deviate from the illumination target, and the laser imaging system will cause image blur and jitter. Similarly, the approaches provided in this chapter will still have the advanced technical merits in the solutions of the aero-optical effects.
