Abstract To figure out the flow characteristics through cracks with narrow and short passage, experimental and theoretical studies were conducted in this study. The leakage flow phenomena such as crack opening enlargement, partial flashing and actual flow region were discovered during the test. The mechanism models were proposed according to the test results. Mechanical model on the COD (crack opening displacement) variation was presented considering the fluid-structure interaction; the entrance resistant coefficient model for cracks was raised, which elaborates the dependence of entrance resistance on stagnation condition and crack opening; non-equilibrium model based on flashing fraction and flashing inception was put forward, taking partial flashing and choking into account; for circumferential crack, flow region was suggested, which increases with stagnation temperature. The above models have been validated and evaluated by the experimental results of this study and from literature. It was proved that, by considering the detailed flow phenomenon and characteristics for cracks with extreme narrow and short passage, these mechanism models significantly improve the prediction accuracy. This study provides a large enhancement on the understanding and prediction of choked flow though micro cracks.

中文翻译：

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流固耦合与微裂纹流动非平衡的实验与理论研究

摘要 为了解窄通道和短通道裂缝的流动特性，本文进行了实验和理论研究。试验过程中发现了裂缝开口扩大、局部闪蒸和实际流动区域等漏流现象。根据试验结果提出了机理模型。考虑流固耦合，提出了COD（裂缝张开位移）变化的力学模型；提出了裂缝入口阻力系数模型，阐述了入口阻力对滞止条件和裂缝张开的依赖性；提出了基于闪蒸分数和闪蒸起始的非平衡模型，考虑了部分闪蒸和阻塞；对于周向裂纹，建议流动区域，它随着停滞温度而增加。上述模型已经通过本研究的实验结果和文献进行了验证和评估。事实证明，这些机理模型通过考虑极窄和短通道裂缝的详细流动现象和特征，显着提高了预测精度。这项研究大大增强了对通过微裂纹的阻塞流的理解和预测。