附壁空泡群的非定常特性会对水下航行体的正常工作状态产生不利影响。研 究空泡群的脱落机制及其与多场作用规律是包括航天在内的多个工业领域亟需解 决的关键问题。得益于计算流体力学的发展，采用精细湍流模拟方法研究空化流 动成为可能。目前，对这类存在宽泛时空尺度变化的多相流模拟还存在一些建模 和求解方面的问题，研究空泡与湍流场的作用方式尚存不足。本文通过严格的数学推导，发展并完善了一套空化问题数值求解方法，基于 开源 CFD 软件 OpenFOAM 进行求解器开发。在模型、算法和应用三个层次论述了对非定常空化现象的系统研究。模型方面，合理简化宏尺度框架下单场模型的控制方程，其中包含湍 流亚格子粘性、空化源项两个未封闭项。基于 Kataoka 的理论推导工作，湍 流控制方程采用单相可压缩形式的改进延迟分离涡混合方法。对于 描述相间传质的空化模型，提出能体现空泡群内部非线性物理特性的新空化模型。表达式中出现生长/溃灭势函数表征各阶段的非线性特性;只需 两个有明确物理意义的模型参数，分别对应于平均空泡动态特性曲线上 的 Blake 临界半径和平均生长最大半径。通过近壁空泡溃灭、超声变幅杆空化证明 了新模型的优越性。算法方面，提出适用于大密度比的同位网格动量插值方法 (MMI)。可防止在 使用小时间步长出现压力震荡问题，还能避免计算结果与时间步长选择的相关性。 应用方面，基于 DES 方法成功模拟平头回转体非定常空泡脱落，准确地捕捉 到空泡群局部性、交替性的脱落规律。重点分析了“回射流”脱落机制和空泡与湍流 场相互作用。发现回射流有明显的三维结构，流向速度是导致空泡脱落的必要条 件，而其引发的周向流动决定了脱落范围。? 等值面显示空泡脱落与肩部大涡的 破碎过程近乎一致，说明涡结构变化决定了空泡的形态。通过统计各向异性雷诺 应力的二阶、三阶不变量发现，在 500 < ?+ < 2500 的区域内，空泡存在改变了湍 流场脉动速度的各向异性，使得流向分量增强而垂直流向两分量减弱。此外，空 化流场中近壁雷诺切应力的减弱是采用 RANS 模型加入湍流粘性修正的主要 原因。通过分析近壁压力脉动均方根发现，在 1? 左右发生脉动的急剧增高，作用于空泡群使其发生不稳定扰动和脱落现象。

The unsteady characteristics of wall-attached cavitation bubbles has adverse effects on the underwater vehicle in normal operation. To study the mechanism of cavitation shedding and its interaction with multiple physical fields are the critical technology which should be solved and developed for many industries including aerospace engineering. Nowadays it is possible to implement the elaborate simulation to investigate the cavitating flows that is benefit from the great progress of computational fluid dynamics. However, there are still some difficulties about modeling and numerical algorithm for such multiphase flow in which exist wide ranges of temporal-spacial scales inherently. And the studies of interactions between bubble cluster and turbulence field are insufficient. On the basis of strict mathematical deduction, a numerical methodology for cavitation flows is improved and perfected, which are further developed the cavitation solver based on the OpenFOAM. In this thesis, systematic research on unsteady cavitation simulations is carried out in three aspects including modeling, algorithm and application. In the aspect of modeling, the OFF macro-scale models, containing two unclosed terms which are turbulent subgrid-scale viscosity and cavitation sources, are simplified through reasonable assumption. Based on the results of theoretical derivation by Kataoka, the hybrid turbulence model of IDDES-SA is employed which governing equation should be used as single-phase compressible fluid formulation. As for the cavitation model, a new model called NDCM is proposed which can reflect the nonlinear physical characteristics of the cavity. The growth/collapse potential functions $(\psi_{v},\psi_{c})$ appeared in the expressions reveal nonlinear features for respective processes. And only two model parameters are employed which can reflect the relevance between cavitation model and actual physical quantities, where $R_{b}$ and $R_{m}$ represent the Blake critical radius and average maximum growth radius on the statistical dynamic characteristic curves. The Superiorities of new cavitation model are illustrated clearly through the simulation cases of near wall bubble cluster collapse and ultrasonic horn. In the aspect of algorithms, a modified momentum interpolation (MMI) method on collocated grid is proposed which is suitable for the multiphase flow with large density ratios. It can prevent pressure oscillations when using small time step, and the dependence between simulation results and time step selection can be avoided. In the aspect of applications, the unsteady cavitating shedding of blunt head slender body is simulated effectively based on the DES hybrid method, which phenomenon of partial and alternating characteristics are captured exactly. The shedding mechanism of "re-entrant jet" and the interaction between bubbles and turbulent field are analyzed. It is found that the jet has evident three-dimensional structures that the streamwise component is requisite to cause bubble detachment whereas the circumferential movement induced by inverse flow determines the shedding position. The contour of Q-criterion is visualized the synchronization between vortex broken and bubble cloud shedding which implies that the bubbles dynamics are mainly affected by local vortex structure. Analyzing the statistics of the second and third order invariants of anisotropic Reynolds stress found that the anisotropy of fluctuating velocity in turbulent field is reformulated by the existence of cavitation bubbles so that the streamwise component is strengthened whereas the two componets of spanwise are weakened in the region of $500