Abstract
Aero-optical effects reduce the accuracy of optical sensors on high-speed aircraft. Current research usually focuses on light refraction caused by large-scale density structures in turbulence. A method for analyzing photon energy scattering caused by micro-scale structures is proposed in this paper, which can explain the macro image distortion caused by moving molecules in inhomogeneous airflow. Quantitative analysis of the propagation equation indicates that micro-scale structures may contribute more to the wavefront distortion than the widely considered large-scale structures. To analyze the micro mechanism of aero-optical effects, a transient simulator is designed based on the scaling model of transient distorted wavefronts and the artificial vortex structure. The simulation results demonstrate that correct aero-optical phenomena can be obtained from the micro mechanism of photon energy scattering. Examples of using the transient simulator to optimize the parameters of the star sensor on a hypersonic vehicle are provided. The proposed analysis method for micro-scale structures provides a new idea for studying the aero-optical effects.
Highlights
With the rapid development of hypersonic vehicles, the measurement errors of optical sensors caused by aero-optical effects have attracted research attention [1,2,3,4,5]
Light refraction is a macro description that cannot accurately reveal the micro mechanism of aero-optical effects because the influence from the scattering of micro-scale structures, which is close to the dissipative scale, is not negligible compared with the refraction caused by large-scale structures [12,13]
The results show that correct aero-optical phenomena can be obtained by the micro mechanism of photon energy scattering
Summary
With the rapid development of hypersonic vehicles, the measurement errors of optical sensors caused by aero-optical effects have attracted research attention [1,2,3,4,5]. The transmission of light through a high-speed flow field is disturbed by the inhomogeneous and time-varying density field, which seriously reduces the imaging quality of the optical sensor and causes image blurring, deviation, and jitter. The cause of aero-optical effects is usually explained as light refraction, and large-scale density structures in turbulence are considered the main contributor [10,11]. Light refraction is a macro description that cannot accurately reveal the micro mechanism of aero-optical effects because the influence from the scattering of micro-scale structures, which is close to the dissipative scale, is not negligible compared with the refraction caused by large-scale structures [12,13]. The high-speed flow field contains plenty of unstable turbulent structures, whose density distribution changes rapidly in both the time and space domains.
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