氧碘激光器腔内边界层分离规律与控制方法

The boundary layer separation of intracavity flow seriously deteriorates the beam quality and operation stability of chemical oxygen-iodine lasers (COIL). In this proposal, fundamental rules governing the boundary layer separation of the flowing lasing media, as well as the aero-optical effects induced by the boundary layer separation control method based on near-wall blowing is explored. Based on the acquired knowledge, the feedback boundary layer control method for COIL is developed for the first time to achieve effective separation control with low blowing flow rate and good output beam quality. This could greatly enhance the applicability of COIL in directed energy weapons..Firstly, numerical model that is capable of catching the boundary layer separation phenomenon of the supersonic flowing lasing media is developed by associating the large-eddy simulation and the Reynolds-averaged Navier-Stokes method. The molecular tagging velocimetry is applied to experimentally verify the proposed model. And the quantitative relationship between the boundary layer separation position and the operation condition of the laser is explored..Then, by further associates the established model with the wave optics methods, the aero-optical effects induced by the boundary layer separation control method is revealed. The optimized blowing flow distribution for achieving boundary layer control with low total blowing flow rate and good output beam quality is obtained for various circumstances with different boundary layer separation positions..Finally, the feedback boundary layer control method for COIL is developed based on the established relationship between the separation position and the operation condition, and the optimized blowing flow distribution related to various boundary layer separation positions. Experiments will be carried out on the kilowatts COIL experimental platform in Key Laboratory of Chemical Lasers, Chinese Academy of Sciences, to prove the effectiveness of the proposed method.

氧碘激光器腔内流场的边界层分离现象严重影响激光器的光束质量和工作稳定性。本项目通过探索腔内边界层分离的产生规律及吹气式边界层控制方法的气动光学效应等基础问题，发展适用于氧碘激光器的反馈式腔内边界层分离控制方法，为提升氧碘激光器在定向能技术中的应用能力探索有效途径。.主要研究内容为：（1）有效结合大涡模拟法和雷诺平均法各自优势，建立准确解析腔内边界层分离现象的数值模型；利用分子标记测速实验对模型进行验证；进而探明边界层分离位置与激光器工作条件之间的规律。（2）进一步结合波动光学模型，建立准确解析腔内高频脉动湍流气动光学效应的数值模型；进而考察不同吹气方式对光束质量的影响，以高光束质量和低吹气流量为目标，确定针对不同分离位置的最优吹气方式。（3）基于所探明的边界层分离位置规律和针对不同分离位置的最优吹气方式，发展反馈式边界层分离控制方法；基于千瓦级氧碘激光实验平台验证其有效性。

氧碘激光器光腔中的边界层一旦分离，会压缩边界层外的流体而造成增益介质不均匀，使激光器光束质量下降。如何抑制光腔中的边界层分离，对于提高氧碘激光器的光束质量和稳定性，提升其在定向能技术中的应用能力具有重要意义。主要研究内容包括：（1）建立准确解析腔内边界层分离现象的数值模型；利用分子标记实验对模型进行验证；进而探明边界层分离位置与激光器工作条件之间的规律。（2）建立准确解析腔内高频脉动湍流气动光学效应的数值模型；确定针对不同分离位置的最优吹气方式。（3）发展反馈式边界层分离控制方法；基于千瓦级氧碘激光实验平台验证其有效性。本项目取得的主要结果包括：建立了LES/RANS流场-化学场耦合模型和光场-LES/RANS流场-化学场耦合模型，已经获得了化学氧碘激光器多物理场耦合模拟仿真软件著作权，计算结果与实验实测结果比较，相对误差在15%以内；获得了氧碘激光器腔内边界层分离规律、边界层的气动光学规律以及抑制边界层分离最佳吹气条件等规律；发展了抑制边界层分离及改善边界层气动光学效应的边界层控制方法，建立了相应的反馈控制系统，并在千瓦级氧碘激光器上验证了控制方法的有效性，激光输出功率增加幅度约3.9%，填充因子（F因子）增加幅度约1.7%。本项目提出的部分技术途径在某重大项目中得到实际应用，显著提高了激光光束质量，获省部级科技进步二等奖。