Computation and analysis of backward ray-tracing in aero-optics flow fields

Area of Science:

• Computational fluid dynamics
• Optical physics
• Aero-optics

Background:

• Aero-optics simulations are crucial for understanding light propagation through turbulent airflow.
• Traditional forward ray-tracing methods can be computationally intensive for complex flow fields.
• Accurate modeling of refractive index variations is essential for predicting optical distortions.

Purpose of the Study:

• To propose and demonstrate a backward ray-tracing method for aero-optics simulations.
• To simplify computational complexity in ray tracing through aero-optical flow fields.
• To establish a foundation for active laser illumination studies using the reciprocity principle.

Main Methods:

• A backward ray-tracing algorithm is developed, initiating from the internal sensor towards the distant target.
• The method traces rays through the internal gas region, aero-optics flow field, and freestream.
• Coordinate values, density, and refractive index are computed at each step, with a stopping criterion at the flow field's edge.

Main Results:

• The backward ray-tracing method significantly simplifies computations compared to forward methods.
• A specific stopping criterion effectively defines the boundary for tracing within the aero-optics flow field.
• Demonstration on a blunt-nosed vehicle validates the method's applicability and efficiency.

Conclusions:

• The proposed backward ray-tracing method offers a computationally efficient approach for aero-optics simulations.
• The developed stopping criterion enhances the practicality of the method.
• The technique is extensible to active laser illumination scenarios due to the principle of reciprocity.