Numerical Simulation Of High Speed Gas-liquid Two-phase Flow Through A Crack

Some defects,such as cracks,voids and inclusions,will inevitably appear on the surface or inside pressure-bearing components such as pipes and pressure vessels.Numerous studies have shown that the phenomenon of stable leakage occurs before fracture,and the study of the flow characteristics within the penetration crack is of practical importance for the design of the LBB and the prevention of major accidents.In this study,the gas-liquid two-phase flow in a rectangular through-crack is visualised by means of numerical simulations and the special phenomenon of single-hole inlet in the rectangular through-crack and extended to simulate the gas-liquid two-phase flow in a bent-angle microchannel.With the help of CFD numerical simulation technology to visualise the details of the flow field,velocity field and pressure field and to understand the characteristics of the gas-liquid two-phase flow within the penetration crack more intuitively,the main research results are:(1)Based on experimental data,the gas-liquid two-phase flow within the penetration crack is simulated under different operating conditions.The CFD simulations were validated by comparison with experimental visualisation images and pressure monitoring data.The simulations show that the gas phase distribution and the experimental visualisation images are in good agreement,and the maximum error in pressure prediction at each pressure measurement point is around 10%.(2)The gas-liquid cross-sectional gas content increases along the range and is negatively correlated with the pressure,the higher the pressure the stronger the compression of the gas and the lower the cross-sectional gas content.(3)The simulation results of the two-phase flow velocity distribution show that there is a clear dividing line between the velocities of the gas and liquid phases,with the velocity of the single-phase liquid on both sides being significantly slower than that of the gas-liquid two-phase mixture in the middle,and the velocity of the two-phase mixture gradually accelerating in the direction of the flow channel and reaching a maximum at the outlet.There is a certain acceleration pressure drop at the exit of the flow channel,and as the gas content increases,the more obvious the acceleration effect at the exit.(4)The special phenomenon of the single-hole intake is due to the fact that the flow resistance of the two holes cannot be identical.Studies on the single-hole intake and double-hole intake conditions show that the difference in pressure drop between the two is not significant,but the average density of the double-hole intake model is higher than that of the single-hole intake model at the same position in the cross-section.(5)The bending angle of the flow channel will have an obstructive effect on the fluid in the channel,and the smaller the angle of the bending angle,the greater the obstructive effect.(6)It is of great engineering importance to estimate the amount of leakage through the channel.CFD numerical simulations can predict the pressure drop in the channel very accurately,but it is still recommended to increase the safety margin when assessing the leakage of the initial crack through the pressure drop.