Abstract The objective of the paper is to investigate the physics involved in the compressible cavitating flows, with emphasis on the compressibility effects. 3-D numerical simulations were conducted on the open source software platform OpenFOAM, using both the native incompressible cavitation solver interPhaseChangeFOAM and implemented compressible cavitation solver, where the cavitation model and turbulence model are kept the same and differences of the two approaches mainly root in the density variances of pure liquid and pure vapor. Results are presented for the transient sheet/cloud cavitating flows around a Clark-Y hydrofoil fixed at attack of angle α=8° at inlet velocity U=10m/s and cavitation number σ=0.8, where both ensemble averaged statistics and transient characteristics are analyzed. Good agreement can be obtained using both the incompressible and compressible approaches when compared with the experiment data. While it is found that compared with the incompressible approach, the compressible approach can predict the unsteady cavitation evolution and cavity shedding frequency better. With the compressibility effects considered, the time averaged void fraction distribution decreases, and the cavity size (i.e. cavitation area) becomes smaller. The re-entrant flow thickness normalized by local cavity thickness predicted by the compressible approach is larger than that by the incompressible approach, indicating that the compressible approach can predict the re-entrant jet dynamics well. The velocity divergence analysis show that compared with that in incompressible approach, where velocity divergence mainly comes from the mass transfer between phases, in compressible approach, the velocity divergence originates from both the cavitation two-phase fluid compressibility and mass transfer, and the fluid density variance dominates in compressible results. Following, the budget analysis of vorticity transport equation (VTE) show that the vortex stretching term dominates the cavitation vortex dynamics. Compressibility effects will significantly increase the dilatation term and decrease baroclinic term by decreasing the misalignment between density gradient and pressure gradient. Finally, the temperature and density variance in different cavitation structures are presented.

中文翻译：

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可压缩空化流的特性和动力学，特别强调可压缩性效应

摘要 本文的目的是研究可压缩空化流中涉及的物理现象，重点是可压缩性效应。在开源软件平台 OpenFOAM 上进行了 3-D 数值模拟，使用原生不可压缩空化求解器 interPhaseChangeFOAM 和实现可压缩空化求解器，其中空化模型和湍流模型保持相同，两种方法的差异主要在于纯液体和纯蒸汽的密度变化。结果显示为在入口速度 U=10m/s 和空化数 σ=0.8 下固定在攻角 α=8° 的 Clark-Y 水翼周围的瞬态片/云空化流，其中集合平均统计和瞬态特性均为分析了。与实验数据相比，使用不可压缩和可压缩方法可以获得良好的一致性。同时发现，与不可压缩方法相比，可压缩方法可以更好地预测非稳态空化演化和空腔脱落频率。考虑到压缩性的影响，时间平均空隙率分布减小，空腔尺寸（即空化面积）变小。可压缩方法预测的局部腔体厚度归一化的回流厚度大于不可压缩方法，表明可压缩方法可以很好地预测再入射流动力学。速度发散分析表明，与不可压缩方法相比，其中速度发散主要来自相间的传质，在可压缩方法中，速度发散源于空化两相流体的可压缩性和传质，并且流体密度方差在可压缩结果中占主导地位。接下来，涡度输运方程 (VTE) 的预算分析表明，涡流拉伸项主导着空化涡流动力学。通过减少密度梯度和压力梯度之间的错位，可压缩性效应将显着增加膨胀项并减少斜压项。最后，给出了不同空化结构中的温度和密度变化。速度发散源于空化两相流体可压缩性和传质，流体密度方差在可压缩结果中占主导地位。接下来，涡度输运方程 (VTE) 的预算分析表明，涡流拉伸项主导着空化涡流动力学。通过减少密度梯度和压力梯度之间的错位，可压缩性效应将显着增加膨胀项并减少斜压项。最后，给出了不同空化结构中的温度和密度变化。速度发散源于空化两相流体可压缩性和传质，流体密度方差在可压缩结果中占主导地位。接下来，涡度输运方程 (VTE) 的预算分析表明，涡流拉伸项主导着空化涡流动力学。通过减少密度梯度和压力梯度之间的错位，可压缩性效应将显着增加膨胀项并减少斜压项。最后，给出了不同空化结构中的温度和密度变化。通过减少密度梯度和压力梯度之间的错位，可压缩性效应将显着增加膨胀项并减少斜压项。最后，给出了不同空化结构中的温度和密度变化。通过减少密度梯度和压力梯度之间的错位，可压缩性效应将显着增加膨胀项并减少斜压项。最后，给出了不同空化结构中的温度和密度变化。