3 rd International Symposium of Cavitation and Multiphase Flow CFD Simulation of Multiphase Flow at Different Scales Minsheng Zhao, Xiaosong Zhang, Xiao Wen, Jianhua Wang, Cheng Liu, Decheng Wan* Collaborative Innovation Center for Advanced Ship and Deep-Sea Exploration, State Key Laboratory of Ocean Engineering, School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University Shanghai, China * Corresponding Author: dcwan@sjtu.edu.cn ABSTRACT Along with advances in computer technology, numerical simulation has been widely used in the analysis of marine hydrodynamic problems, especially for the multiphase flow. According to the resolution-scales, the simulation of multiphase flow can be performed in macroscale, mesoscale and microscale, corresponding numerical methods, i.e. the RANS/DES approach with VOF method, Euler-Lagrange method, Moving Particle Semi-implicit (MPS) method and DNS method, are demonstrated in the present paper. The numerical results obtained by those methods are in consistent with the experimental ones and other’s research. It is concluded that with further development of theoretical study and numerical methods, the present numerical methods can deal with complex multiphase flow problems in multiple scales. Efficiency and accuracy need to be focused in the future development of the numerical model and CFD solver. KEY WORDS: Multiphase flow; cavitation; breaking wave; bubble flow; MPS method INTRODUCTION Multiphase flows are complex phenomena and can be found in a variety of situations, both in natural and industrial process. The complexity of multiphase flow increases with the presence of multiscale turbulence, large-density- ratio two-phase flow and complicated boundaries. Although the research of multiphase flow is challenging, related studies are of great importance in theoretical analysis and practical applications for the development of many interfacial-flow-equipment. In the field of ship and ocean engineering, there are many topics related to multiphase flow and its branches. The wave-making of surface ships, wave-structure interaction, breaking waves, bubble flow and cavitation, are typical features of multiphase flow in ship and ocean engineering. The in-depth study of gas-liquid two-phase flow lays a foundation for numerical simulation of various multiphase flows. The multiphase flow can be classified into three categories according to the resolved flow feature scales, i.e. macroscale, mesoscale and microscale multiphase flows. The macroscale multiphase flow is mainly computed through relatively simplified models, where the interface is not actually tracked. The Volume of Fluid (VOF) method is one of the approaches for macroscale multiphase flow. The mesoscale flow is generally resolved by the Euler-Lagrange method, while the microscale multiphase flow is that all the interface features are computed directly. The meshless method, such as MPS and SPH method, can give the detailed description of the microscale features since the interface is actually tracked. The DNS approach can also be one of the approaches to predict the microscale multiphase flow behavior. Over the past decade, the Computational Marine Hydrodynamics Lab (CMHL) in Shanghai Jiao Tong University has focused on the development of numerical schemes and solvers related to multiphase flow. So far, the self-developed CFD solvers have been successfully applied to the numerical study on different scales of multi-phase flows, such as ship hydrodynamics, cavitation flow, offshore platform in waves, wave-breaking and floating offshore wind turbines. The recent progress on numerical simulation of multiphase flow at different scales by CMHL are demonstrated in the present paper, where the cavitation flow and ship breaking bow waves at macroscale, bubble flow at mesoscale and various multiphase flows at microscale are illustrated in detail. MACROSCALE FLOW Breaking Wave