Experimental and theoretical study on fluid-structure interaction and non-equilibrium of the flow through micro cracks

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.