Progress and key influencing factors in vortex separator technologies: A comprehensive review on optimization and similarity principles.

Vortex separators have become indispensable small units for the treatment of multiphase streams and particle-laden flows in wastewater, stormwater management and environmental protection industries. Despite the vast application, there is not yet a unified understanding of the joint control of separation performance and similarity scaling by structural configuration, operational parameters, and characteristics of particles. This review synthesizes new developments based on inlet-outlet configurations, internal baffling and vortex-forming elements, along with key hydraulic variables including surface loading rate, hydraulic retention time and inflow velocity over wide ranges of particle sizes, densities and concentrations. The analysis uncovers mechanistic relationships of the flow structure, turbulence and particle trajectories. Principal dimensionless parameters particularly Peclet number (Pe), Reynolds number (Re), and Froude number (Fr) are identified for enabling performance transfer from laboratory models to full-scale systems. The research establishes that meaningful optimization involves simultaneous consideration of the structural, hydraulic and particle domains. Future directions in theoretical development and structural innovation are provided to guide vortex separator design for the next generation.