As a flow display technique, the silk thread method can clearly show the state of the flow field. However, displaying the state of the flow field in industrial closed metal cavities is impossible, and results of the traditional silk thread method fail to present depth information. To address these limitations, we propose a display method based on γ-photon silk thread 3D imaging. Firstly, a flow field visualization experimental platform applicable for industrial closed metal cavity was designed. Then, aiming at the shortcomings of insufficient γ-photon scanning data and limited imaging quality in flow field visualization, an adaptive sinogram interpolation-iterative filtering reconstruction algorithm was proposed to expand the data via the adaptive interpolation processing of the sinogram in image reconstruction. Beltrami filtering was also embedded in the iterative algorithm to effectively reduce noise and artifacts in the imaging image. Finally, the internal flow field inspection of the NACA0018 airfoil and the industrial confinement turbine were used as examples to visualise the wing upper surface flow and turbine blade passage secondary flow, respectively, and the results were consistent with those of the numerical simulation analysis. As the angle of attack of the wing increased, laminar flow separation occurred, and the silk thread structure state changed to the point where the aircraft stalled. After the imaging map analysis, the stall angle ranged between (15,19), which is consistent with the simulation results. In the turbine blade passage secondary flow detection, the imaging map formed a horseshoe vortex with airflow separation at the central saddle point and silk threads clearly presenting the structural state of the flow field along different directions.

中文翻译：

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基于γ光子丝线法的3D成像在流场可视化与检测中的应用研究

丝线法作为一种流场显示技术，可以清晰地显示流场的状态。然而，无法显示工业封闭金属腔体中的流场状态，并且传统丝线方法的结果无法呈现深度信息。为了解决这些限制，我们提出了一种基于γ光子丝线3D成像的显示方法。首先设计了适用于工业封闭金属腔体的流场可视化实验平台。然后，针对流场可视化中γ光子扫描数据不足、成像质量有限的缺点，提出一种自适应正弦图插值-迭代滤波重建算法，通过图像重建中正弦图的自适应插值处理来扩展数据。迭代算法中还嵌入了Beltrami滤波，可有效减少成像图像中的噪声和伪影。最后以NACA0018翼型和工业约束涡轮的内部流场检查为例，分别对机翼上表面流动和涡轮叶片通道二次流进行可视化，结果与数值模拟分析结果一致。随着机翼迎角的增大，发生层流分离，丝线结构状态发生变化，直至飞机失速。经过成像图分析，失速角范围在（15，19）之间，与仿真结果一致。在涡轮叶片通道二次流检测中，成像图形成中心鞍点处气流分离的马蹄形涡流，丝线清晰地呈现出不同方向流场的结构状态。