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In this study, the performance of a pump-jet propulsor (PJP) with pre-swirl stator in open water is numerically investigated. Both full-scale and model-scale configurations are considered. The Reynolds-averaged Navier–Stokes equations and shear stress transport [Formula: see text] turbulence model are used in the numerical calculation. The computational domain is discretized using structured grids, and a rotating grid is affixed to the rotor to deal with the relative motion between the rotor and stationary components. The mesh quality is determined based on a grid uncertainty analysis. The numerical method is validated using model-scale experimental data. The simulation results reveal the influences of the scale size on the hydrodynamic performance and the distributions of the velocity, pressure and vorticity under three advance coefficients. With the increase in the advance coefficients, the scale influences on the efficiency become more obvious, and the efficiency of the full-scale PJP is always higher than that of the model-scale PJP. The full-scale configuration is found with a more significant instability in the gap vortex development, because it presents larger interaction between tip leakage vortex (TLV) and the inner wall of the duct. As the main velocity increases, the TLV shedding is delayed. Finally, the development process of gap vortices is analyzed for the difference operation conditions.

Pipeline vibration induced by fluid flow can cause pipeline fatigue damage, which seriously endangers the safety of the operation. This paper aims to clarify the dynamic variation law of pipeline vibration induced by gas-liquid two-phase flow in the elbow and the influence of different gas-liquid ratios on the dynamic evolution of two-phase flow patterns. The volume of Fluid (VOF) method and C-C algorithm capture the flow pattern characteristics and reconstruct the flow pattern phase space respectively, further exploring the complex information of dynamic flow pattern evolution. The chaotic characteristics of each flow pattern are analyzed according to the maximum Lyapunov exponent. The vibration characteristic mechanism corresponding to the evolution of the flow pattern is explored based on the time and frequency domain, and the origin exciting force of the elbow is explored according to the momentum balance equation. The simulation results show that the VOF method can well capture the characteristics of slug flow developed by the interphase instability mechanism. After phase space reconstruction, the dynamic evolution mechanism of the flow pattern is complex and the chaotic characteristics of slug flow are strong. The flow pattern evolution is related to the increase in wave height. The superficial velocity of the liquid phase is more sensitive to the flow pattern formation mechanism than the gas phas'e. The amplitude of the wave strongly depends on the Vsg and Vsl. There is a strong correlation between the main exciting force pulsation and momentum flux pulsation.