• Cavitation flow in an ARHCR is studied combining flow visualization and CFD. • Cavitation is characterized by the periodic motion of CGUs. • Cavitation development process shows high periodicity from flow visualization. • Vortex cavitation is generated at the vortex center of CGUs. • Sheet cavitation is induced in the flow separation region of downstream CGUs.

• A novel rotor-radial groove (RRG) hydrodynamic cavitation reactor was proposed with good cavitation intensity and energy utilization. • The cavitation performance of rectangular-shaped CGU was better than the cylindrical-shaped CGU. • The cavitation performance could be improved more effectively by increasing the rotor speed and decreasing the interaction distance.

With the development of industry and the rapid growth of population, the current water treatment technologies face many challenges. Hydrodynamic cavitation as a green and efficient means of water treatment has attracted much attention. During the hydrodynamic cavitation, enormous energy could be released into the surrounding liquid which causes thermal effects (local hotspots with 4600 K), mechanical effects (pressures of 1500 bar) and chemical effects (hydroxyl radicals). These conditions can degrade bacteria and organic substance in sewage. Moreover, the combination of hydrodynamic cavitation and other water treatment methods can produce a coupling effect. In this review, we summarize the methods of hydrodynamic cavitation and the performance of water treatment for different types of sewage. The application of hydrodynamic cavitation reactors with different structures in water treatment are also evaluated and discussed. The design and optimization of high-performance hydrodynamic cavitation reactor are the most crucial issues for the application of hydrodynamic cavitation in water treatment. Finally, recommendations are provided for the future progress of hydrodynamic cavitation for water treatment.

In order to improve the simulation accuracy of scroll compressors, a novel mesh-generation method of structured dynamic mesh (SDM) is proposed for fluid domains of scroll compressors in this paper. High-quality and density meshes are generated using the SDM in the fluid domains, especially in the flank meshing clearance between wrap profiles in the orbiting and fixed scrolls. The mesh generation process is presented, including scroll solid boundary of fluid domains, structured mesh dividing method in normal and tangent direction, and motion equations of each layer of nodes. Based on the SDM, numerical simulation of an unsteady compressible viscous turbulent flow with moving boundaries in the working process of scroll compressors is carried out, and the overall flow distributions of pressure, temperature and velocity are obtained. The study results show that the numerical simulation using the SDM is more accurate than using the existing unstructured dynamic mesh. The results are significant to predict, exhibit and reveal flow fields in the fluid domain of scroll compressors.