The present work is focused on the analysis of cloud cavitation, i.e. high-speed unsteady liquid /vapor flows characterized by periodical large-scale shedding. The study relies on the numerical modeling of cavitating flows with a homogeneous approach coupled with the Reynolds-Averaged Navier-Stokes (RANS) framework. A new algorithm based on an implicit fractional step method is used to solve the time-dependent mass, momentum and transport equation for the void fraction. It is combined with an original treatment of the cavitation source term, which enables to maintain the void fraction within its physical range [0 1] throughout the calculation. No artificial numerical limitation is applied, so the overall mass conservation of the method is not deteriorated. The influence of the turbulence modeling on the results is investigated by applying a k-ε RNG and a k-ω SST model with and without the modification of the turbulent viscosity proposed by Reboud et al.[1,2]. Cavitation on a 2D Venturi type section and a NACA hydrofoil are both considered. The present work confirms the capability of the modified k-ε RNG and k-ω SST models to reproduce the main features of cloud cavitation. The role of the transport of principal turbulent shear stress in the mechanism of flow unsteadiness is discussed, as well as the validity of the Bradshaw's assumption for adverse pressure gradient. The benefit and the limitations of the modification of the turbulent viscosity are shown: while it enables to reproduce the main features of the flow behavior, significant discrepancies in the local shear stress are still found.

目前的工作集中在对云空化的分析上，即以周期性大范围脱落为特征的高速非稳态液体/蒸气流。该研究依靠空化流的数值模型，采用均质方法结合雷诺平均Navier-Stokes（RANS）框架。提出了一种基于隐式分数步法的新算法来求解空隙率随时间的质量，动量和输运方程。它与空化源项的原始处理相结合，可以在整个计算过程中将空隙率保持在其物理范围[0 1]中。由于没有人为的数值限制，因此该方法的整体质量守恒不变。通过应用k-εRNG和k-ωSST模型研究湍流模型对结果的影响，该模型具有和不具有由Reboud等人提出的[1,2]修改的湍流粘度。均考虑了二维文丘里管型截面上的气蚀和NACA水翼型。本工作证实了修改后的k-εRNG和k-ωSST模型具有再现云空化的主要特征的能力。讨论了主要湍流剪切应力的传递在流动不稳定机理中的作用，以及Bradshaw假设的逆压力梯度假设的有效性。示出了改变湍流粘度的益处和局限性：尽管它能够再现流动行为的主要特征，但是仍然发现局部剪切应力的显着差异。