Fluid sloshing negatively impacts the stability and safety of liquid hydrogen during transportation. Computational fluid dynamics (CFD) analysis is employed to investigate the sloshing behavior in cargo and fuel storage tanks. Key influencing factors include liquid hydrogen fill level, wave amplitude and frequency, and tank design parameters. Rib structures are incorporated into transportation tanks to mitigate sloshing, although their installation may compromise structural integrity. To address this, CFD methods are integrated with metamodels and artificial intelligence (AI) models to optimize rib design, balancing sloshing suppression and structural stability. In this study, a random forest algorithm predicts optimal rib configurations with a error margin of 3.3

Cavitation vortex dynamics play a vital role in the hydraulic efficiency and reliability of Francis turbines, particularly under variable operating conditions. This study investigates the formation, evolution, and impact of cavitation-induced vortex rope within the turbine flow passages. Computational fluid dynamics (CFD) simulations are conducted to evaluate the interactions between pressure fluctuations, turbulence intensity, and vortex formation at different operating loads. By assessing the behavior of vortex rope under flexible operating conditions, the study aims to identify critical parameters that affect cavitation inception and propagation. Results indicate that low-pressure regions and flow instabilities contribute to the development of unsteady vortex structures, influencing hydraulic performance and operational efficiency. Furthermore, optimization strategies, such as flow control techniques and blade modifications, are explored to mitigate the adverse effects of cavitation. The findings offer valuable insights into enhancing turbine longevity and minimizing efficiency losses from cavitation vortex formation. This research enhances the understanding of hydrodynamic instabilities in Francis hydro turbines and supports the development of strategies to control cavitation effects, ensuring stable and highperformance turbine operations in varying hydraulic conditions.

Unsteady flow phenomena, such as von Karman vortex shedding at the trailing edge of Francis turbine runner blades, can induce pressure fluctuations, acoustic emissions, and structural vibrations, thereby compromising operational stability and efficiency. This study examines the impact of trailing edge modification on vortex shedding behavior and associated hydrodynamic instabilities. A Francis turbine model was developed and analyzed using high-fidelity CFD simulations under steady and transient conditions, employing SST and LES turbulence models. The three modified trailing edge geometries (Karman cuts) were compared with the original design to assess their influence on flow structure, pressure fluctuation, and frequency characteristics. Results indicate that trailing edge modifications significantly reduce vortex intensity, streamline distortion, and pressure oscillation amplitude at both the runner trailing edge and draft tube inlet. Furthermore, pressure fluctuation, sound pressure level, and sound amplitude are reduced significantly with trailing edge modification. The geometric modifications at the trailing edge enhance hydraulic stability, improve energy transfer, and reduce vibration-induced fatigue, offering a practical design strategy for high-performance Francis turbines.

Modern Francis turbines play a crucial role in stabilizing power grid through flexible operation. However, flexible operation often requires running under off-design conditions and undergoing frequent transient operations. These regimes expose the turbine to instabilities, primarily associated with cavitation vortex ropes and Rotor–Stator Interactions (RSI), which lead to pressure fluctuations, vibrations, and even resonance. These issues can cause erosion, fatigue failure, and structural damage, and may even destabilize the power grid. Accordingly, achieving flexible operation relies on two complementary approaches: assessing and avoiding unstable operating conditions, and mitigating instability to acceptable levels. In recent years, significant advances have been achieved through experimental investigations and numerical simulations with reduced-scale model turbine, and collaborative projects aimed at extending the stable operating range. This review provides a comprehensive overview of state-of-the-art understanding of instabilities during off design and transient operations in Francis turbines, as well as technologies and methods proposed to mitigate these phenomena, and it finally outlines future research directions.

The demand for pump turbines is increasing to eradicate the fluctuating, unpredictable, and delocalized energy production from wind and solar. The pump turbine design and the geometrical shape (diameter and width ratios) are based on specific speeds. The pump turbine's specific speed directly influenced hydraulic performance and internal flow behavior. Besides hydraulic performance and internal flow, the pump turbine encounters the S-Curve region when operating at a partial flow rate in turbine mode. The S-Curve region is sensitive to the geometrical shape of the pump turbine. At S-Curve region and partial flow conditions, the high specific speed pump turbine has better flow characteristics than a low specific speed pump turbine.

High pumping performance is essential for the boiler in industrial processes and thermal power plants. The multistage centrifugal pump is one of the options for the boiler feed pump because it can deliver a wide range of head and flow rates. The boiler feed pump operates at a wide range of temperatures, and the working fluid properties are sensitive to the temperature. The change in the thermodynamic properties of the working fluid (viscosity, density, and thermal conductivity) will affect the head and efficiency of the multistage centrifugal pump. Besides the hydraulic performance of multistage centrifugal pumps, the thermodynamic properties of the working fluid will adversely affect the structural stability of the pump. It is necessary to understand the influence of working fluid thermodynamic properties on the performance of a multistage centrifugal pump to design and operate the pump appropriately.

Regenerative blowers can produce a high head with a small flow rate, which makes them desirable compared to positive displacement pumps. The regenerative blower consists of an impeller and casing. The impeller shape contributes to the performance of the regenerative blower. CFD analysis is conducted to investigate the effect of geometrical modification on the operating condition of regenerative blowers like head, power, and efficiency. The geometry modification of the regenerative blower is achieved by varying the impeller blade curvature radius, blade inclination angle, blade shape (curved, radially straight, and chevron), and impeller disk side gap passage shape. The various impeller blades and impeller disk side gap passage designs were selected and conducted the CFD analysis to evaluate the regenerative blower performance and internal flow behavior. Study results show that changing the blade shape from curved to radially straight type can improve the blower’s performance.

A screw centrifugal pump is a non-clog type pump known as the sewage pump to transfer solids such as rags, hair, clusters of stringy material, and digested sludge applications. With the large and open channel from suction to discharge, the screw centrifugal pump shows better solids transferring capability, even the sensitive products such as food (tomato, potato), live fish, eel, shrimp. However, the impeller blade inlet of screw centrifugal pump with the high rotation speed can damage the live fish or food. Therefore, in this study, the impeller blade inlet shapes are investigated for their influence on the performance of the live fish transfer pump. The straight, concave, and convex blade inlet shapes are created. Numerical analysis was conducted to study the pump hydraulic and suction performances according to the impeller blade inlet shapes of the screw centrifugal pump.