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The sink vortex with a free surface exists some physical processes in the suction evolution process, such as multiphase coupling, mass transfer, and intensive energy exchange. Here, the transport mechanism of multiphase coupling is a complex dynamics problem with highly nonlinear characteristics. The mechanical modeling and numerical solution of multiphase viscous coupled transport face a significant challenge. To address the above problem, a multiphase coupling transport modeling-solving method of the free sink vortex is proposed. Based on the coupled level set and volume-of-fluid (CLSVOF) method, a multiphase coupling transport model of the free sink vortex is set up with a continuous surface tension model and a realizable (<em>k</em>-<em>ε</em>) turbulence model. An effective volumetric correction scheme calculates the high-speed rotating flow and ensures the mass conservation of flow fields and the velocity field without divergence. Then, an interphase coupling solution approach accurately traces the multiphase fluid distribution and multiphase interface. The multiphase coupling interface and cross-scale vortex cluster transport laws are obtained according to the multi-characteristic physical variables. The interaction mechanism between the multiphase coupling transport process and the pressure pulsation characteristics is revealed. The results show that the multiphase coupling transport is the critical state of the fluid medium transition. The vortex microclusters are subjected to different spatiotemporal disturbance modes and form the layered threaded waveforms at the interface. With the increment of the nozzle sizes, the multiphase coupling process enhances, and the coupling energy shock causes nonlinear pressure pulsation. It can offer valuable references to the research works of the vortex transport mechanism, cross-scale solution of vortex cluster, and flow pattern tracking.

The energy-conversion stability of hydropower is critical to satisfy the growing demand for electricity. In low-head hydropower plants, a gravitational surface vortex is easily generated, which causes irregular shock vibrations that damage turbine performance and input-flow stability. The gravitational surface vortex is a complex fluid dynamic problem with high nonlinear features. Here, we thoroughly investigate its essential hydrodynamic properties, such as Ekman layer transport, heat/mass transfer, pressure pulsation, and vortex-induced vibration, and we note some significant scientific issues as well as future research directions and opportunities. Our findings show that the turbulent Ekman layer analytical solution and vortex multi-scale modeling technology, the working condition of the vortex across the scale heat/mass transfer mechanism, the high-precision measurement technology for high-speed turbulent vortexes, and the gas–liquid–solid three-phase vortex dynamics model are the main research directions. The vortex-induced vibration transition mechanism of particle flow in complex restricted pipelines, as well as the improvement of signal processing algorithms and a better design of anti-spin/vortex elimination devices, continue to draw attention. The relevant result can offer a helpful reference for fluid-induced vibration detection and provide a technical solution for hydropower energy conversion.

Multiphase vortices are widely present in the metallurgical pouring processes, chemical material extraction, hydroelectric power plant energy conversion, and other engineering fields. Its critical state detection is of great significance in improving product yield and resource utilization. However, the multiphase vortex is a complex dynamics problem with highly nonlinear features, and its fluid-induced vibration-generation mechanism faces significant challenges. A fluid-solid coupling-based modeling method is proposed to explore mass transfer process with the vorticity distribution and vibration-generation mechanism. A vibration-processing method is utilized to discuss the four flow-state transition features. A fluid-induced vibration experiment platform is established to verify the numerical results. It is found that the proposed modeling method can better reveal the vibration-evolution regularities of the fluid-solid coupling process. The flow field has a maximum value in the complex water–oil–gas coupled flow process, and induces a pressure pulsation phenomenon, and its frequency amplitude is much larger than that of the water phase and water–oil two-phase flow states. In the critical generation state, the increasing amplitude and nonlinear step structure of high-frequency bands (45 Hz~50 Hz) and random pulse components can be used for the online detection of multiphase-coupling states.

Fluid-induced vibration detection technology for the multiphase sink vortex can help achieve efficient, safe, and low-carbon sustainable industrial production in various areas such as the marine, aerospace, and metallurgy industries. This paper systematically describes the basic principles and research status in light of the important issues related to this technology in recent years. The primary issues that occur in practical application are highlighted. The vital technologies involved, such as the vortex-formation mechanism, interface dynamic evolution, the shock vibration response of thin-walled shells, and vortex-induced vibration signal processing algorithms, are analyzed. Based on in-depth knowledge of the technology, some significant scientific challenges are investigated, and further research prospects are suggested. The research results show that this technology can achieve the real-time detection of vortex-induced vibration states. Two future research directions are those of exploring multiphysical field coupling under harsh conditions and more accurate modeling methods for multiphase coupling interfaces. Regarding vortex-induced vibration, forced-vibration characters with various restriction conditions, the forced-vibration displacement response of liquid-filled shells, intrinsic properties influenced by random excitation forces, and highly effective distortion-detection algorithms will continue to attract more attention. The associated results could give technical support to various fields, including energy-efficiency improvement in manufacturing processes, tidal power generation condition monitoring, and the performance optimization of low-carbon energy components.