| When the ray propagates in the inhomogeneous refractive index flow fields,the aero-optical effects such as aberration and jitter will occurred.The aero-optical effects will have a serious impact on the directional strike capability of laser weapons,optical imaging guidance,and optical imaging detection.Therefore,it is of great practical significance to study the transmission characteristics in the supersonic aero-optical flow field.The research of this paper are as follows:Cellular automata(CA)ray tracing algorithm is proposed in this pap er for aero-optical calculation in the discrete flow fields,Based on the shear layer flow field generated by NPLS(Nanoparticle-based Planar Laser Scattering)and the flow field surrounding the optical dome obtained by DES(Detached Eddy Simulation),The two-dimensional cellular automata algorithm and numerically solving the ray equation algorithm are used to calculate the ray tracing in supersonic boundary layer,mixing layer and the section of the flow field surrounding the optical dome.Then the refractive index field is integrated along the beam path to obtain the optical path length(OPL).The optical path difference(OPD)is calculated from OPL.Unlike numerically solving the ray equation,in CA algorithm,the coordinate value and the offset angle are calculated according to the position and direction evolution rules in CA algorithm.The root mean square error of the OPD between the two algorithms in different flow fields is less than 0.1 wavelength,and the fitting degree is over 85%,it can be seen that the cellular automata algorithm is applicable in the twodimensional flow field and has high calculation accuracy.The twodimensional cellular automata algorithm also has higher computational efficiency than the traditional algorithm by comparing the time complexity and the program running time under the same computer configuration.The average program running time of cellular automata is only about 1/4 of the numerically solving the ray equation.Since in practical applications,the calculation of ray tracing in the aero-optical flow field is mostly three-dimensional flow fields,which are more complex and require more calculation.Therefore,this paper proposes a three-dimensional ray tracing algorithm to calculate the ray tracing near the flow field surrounding the three-dimensional optical dome.Threedimensional ray tracing is calculated in the selected area near the optical window.Then the optical path difference obtained by the two Threedimensional ray tracing algorithms and the algorithm complexity,the program running times are compared and analyzed.The root mean square error of the OPD between the two algorithms is less than 0.1 wavelength,and the fitting degree is over 90%.The results show that the threedimensional cellular automata algorithm is not only has higher calculation accuracy,but also has higher computational efficiency.The results show Three-dimensional cellular automata ray tracing algorithm is suitable for ray tracing in three-dimensional flow field,which provides a new idea for aero-optics calculation in discrete inhomogeneous flow field. |
