Abstract Unsteady turbulent flows in a waterjet propulsion system are investigated at various cruising speeds with the emphasis on pressure fluctuations. The numerical methodology is based on the Reynolds-Averaged Navier-Stokes (RANS) equation with the SST k-ω turbulence model and a sliding mesh technique. The head and efficiency of the waterjet pump are predicted fairly well compared with the available experimental data. The pressure fluctuates intensively in the impeller and the dominant frequency is the impeller rotating frequency with the largest amplitude near the impeller inlet. Besides, two dominant frequency components exist in the intake duct and the diffuser. A high-frequency component is caused by the rotor-stator interaction, and another component is generated by the unsteady vortex evolution in the diffuser passage and would propagate upstream to the impeller and the intake duct. Analyses based on the vorticity transport equation demonstrate the great contribution of the vortex stretching term to the vorticity distribution and evolution in the diffuser. Finally, at the cruising speed of 45 knot, the flows inside the duct are strongly affected by the impeller rotation and present a periodic prewhirl motion with the dominant frequency of the impeller rotating frequency.

中文翻译：

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不同巡航速度下喷水推进系统非定常内部流动特性的研究

摘要 研究了在不同巡航速度下水刀推进系统中的不稳定湍流，重点是压力波动。数值方法基于具有 SST k-ω 湍流模型和滑动网格技术的 Reynolds-Averaged Navier-Stokes (RANS) 方程。与可用的实验数据相比，水刀泵的扬程和效率预测得相当好。叶轮内压力波动剧烈，主导频率为叶轮进口附近振幅最大的叶轮旋转频率。此外，进气管和扩散器中存在两个主频率分量。高频分量是由转子-定子相互作用引起的，另一个分量是由扩散器通道中不稳定的涡流演变产生的，并将向上游传播到叶轮和进气管。基于涡度输运方程的分析表明，涡流拉伸项对扩散器中的涡度分布和演化有很大贡献。最后，在45节的巡航速度下，管道内的流动受到叶轮旋转的强烈影响，并呈现出以叶轮旋转频率为主频率的周期性预旋运动。