# Correction of Aero-Optical Effect with Blow-Suction Control for Hypersonic Vehicles
## 4 Results and Discussion
### With Suction-Controlled Aero-Optical Effect Correction  
According to the prediction, the implementation of inspiratory control will further suppress the development of large-scale vortex structures, resulting in a more flattened disturbed flow field near the window. The stratification along the \(z\)-axis will become more pronounced, and density fluctuations will be further reduced. In high Mach number flight, one of the primary challenges for optical detection is mitigating aerodynamic thermal radiation effects on optical windows. Figure 26 illustrates the temperature distribution across the window, with suction control applied. It can be observed that with or without MVGs, adding suction control to the compression corner downstream effectively maintains  
Figure 25: Comparison of optical wavefront aberration under different flow field conditions (Case0–Case2 conditions without MVGs, Case10–Case12 conditions with MVGs). a low window temperature gradient. Compared to Figure 21b, there is an enhanced uniformity in the window temperature distribution achieved through this approach. The spatial distribution of the density field in the vicinity of the hypersonic/supersonic optical window directly influences its optical detection performance. However, when employing jet cooling and inspiratory rectification in the optical window, it not only introduces complex flow field structures such as shock waves and expansion waves but also experiences influences from mixed layers and turbulent boundary layers, resulting in a more pronounced spatial non-uniformity in the density field. Therefore, studying the refractive index field derived from the density field becomes crucial. Figure 27 illustrates the distribution of refractive index near the optical window under blowing-suction refrigeration control. In this figure, due to inspiratory control at the downstream compression corner of the window, there is an absence of observed complex flow field structures. Comparing with Figures 22a and 24a, the fluctuations in refractive index within the flow field are reduced while exhibiting a more distinct longitudinal distribution. The disturbance of the flow field at the compression corner downstream of the window is clearly evident in Figure 28 below. However, it can be observed that the inspiratory control in other regions of the window at \(Ma=3\) does not significantly enhance the refractive index fluctuation results of the flow field. The flow results at higher Mach numbers reveal the significant impact of the inspiratory disturbance downstream of the window on the density distribution throughout the boundary layer. Figure 29b demonstrates a high-density region extending from upstream to the tail of the window near its wall, providing evidence for how this inspiratory disturbance contributes to stratification within the flow field and facilitates a reduction in phase inequ  
Figure 28: Comparison of refractive index distribution near the optical window under \(Ma=3\): (**a**) without suction, (**b**) with suction. Figure 27: Comparison of refractive index distribution near the optical window: (**a**) \(Ma=3\), (**b**) \(Ma=5\). Figure 26: Comparison of optical window temperature distribution (**a**) without MVGs and (**b**) with MVGs under blow–suction cooling control at \(Ma=3\). The following three comparison diagrams depict the wavefront distortion results under three conditions: only the jet without any inspiratory disturbance at 3 Ma, the addition of inspiratory disturbance, and the inclusion of MVGs and inspiratory disturbance, as illustrated in Figure 30. It is observed that incorporating an inspiratory disturbance can effectively reduce both the average and maximum values of wavefront distortion by 14.7%. A careful analysis reveals that although the mean value of wavefront distortion can be reduced, there remains an increasing trend in distortion along the flow direction. This phenomenon arises due to a larger distance between the shock layer and downstream window caused by outer shock waves.