The aim of this paper is to study the influence of non-uniform suction flow on the transient characteristics of a vertical axial-flow pump device. The unsteady calculation is employed to forecast the unstable flow structure with three inlet deflection angles $\alpha$, and the calculation accuracy under uniform inlet flow is verified by the external characteristic test. The results depict that a promotion in the $\alpha$ will increase the head and shaft power and thus improve the stress and fatigue failure risk of the impeller. At the impeller inlet, the pressure pulsation intensity (PPI) with $\alpha$ = 40° is lower than that with $\alpha$ = 0° caused by a decline in the axial velocity. The dominant frequency of the unsteady pressure signal is the blade-passing frequency (BPF), and the dominant frequency amplitude rises with the increase in $\alpha$ due to the improvement of the pre-rotation impact intensity. At the guide vanes inlet, the dominant frequency of the unsteady pressure signal at the guide vane inlet is also the blade-passing frequency. An improvement in $\alpha$ magnifies the angle between the trailing edge jet of the impeller and the leading edge of the guide vanes under 0.8Q_des and 1.0Q_des, while it diminishes the angle under 1.2Q_des. Thus, the PPI and dominant frequency amplitude with $\alpha$ = 40° are higher than that with $\alpha$ = 0° under 0.8Q_des and 1.0Q_des, but these are lower than that with $\alpha$ = 0° under 1.2Q_des.

A non-uniform velocity profile occurs at the inlet of a coastal axial-flow pump which is placed downstream of the forebay with side-intake. As a result, the actual efficiency and head of the pump is dissimilar to the design parameters, and the lack of the theoretical investigation on the relationship between inflow distortion and energy losses restricts the application of the coastal axial-flow pump in the drainage project. In this paper, the unsteady numerical simulation and entropy production theory are employed to obtain the internal flow structure and quantify energy losses, respectively, with three inflow deflection angles ($\theta$ = 0°, 15°, or 30°). It is reported that the best efficiency point (BEP) shifts to large flow rate with $\theta$ increasing, due to the decline of the velocity component in axial direction at the impeller inlet. Therefore, the total entropy production (TEP) of the coastal axial-flow pump rises with $\theta$ increasing under small flow rates, but it decreases with $\theta$ increasing under large flow rates. The high total entropy production rate (TEPR) in the vicinity of the tailing edge of the impeller and guide vanes rises with $\theta$ increasing, caused by the enhanced wake vortex strength. In addition, the high TEPR area near the inlet of outflow conduit rises with $\theta$ increasing, originated from the improvement of secondary vortices intensity.

This study comprehensively investigates the flow features and energy loss mechanisms under stall conditions based on computational fluid dynamics (CFD) and hydraulic loss visualisation techniques. The three-dimensional unsteady Reynolds-averaged Navier-Stokes (URANS) equations were solved using the shear stress transport (SST) k-ω turbulence model. Furthermore, the entire flow domain of the vertical volute pump was considered to capture the boundary flow behaviour accurately. The results illustrate that the critical stall condition occurs at 0.7Qd, where the H-Q curve exhibits a positive slope, and the deep stall condition occurs at 0.65Qd. The growth rate of energy loss from critical stall to deep stall is 182.2%. In the stall condition, a secondary vortex appears at the impeller inlet. A high energy loss occurs at the suction side and trailing edge in the impeller caused by the reduction in the effective inflow area. The energy loss in the blade suction side guide vane is primarily due to the friction loss under the critical stall condition. By contrast, under the deep stall condition, the energy loss in the outlet of the guide vane is mainly the impact loss from the volute of the rear gunner. The impact effect can result in high energy losses near the volute tongue. The entropy production analysis demonstrates that the hydraulic losses in the diffuser are literately greater than that in the impeller and inlet pipe. Hence, an optimization of such components can be taken into consideration in future works for performance improvement.

In the present work, unsteady flow solved by the Reynolds time-averaged Navier–Stokes equation was investigated to determine the inflow distortion mechanism and the spatial distribution of hydraulic loss in a bidirectional axial flow pumping station (Case 1) based on the entropy production theory. A laboratory-scale performance experiment was also employed for the accuracy verification of the simulation approach, and an axial flow pump with pipe passages (Case 2) accompanying uniform inflow was utilized for analysis comparison. The results show that the non-uniform inflow causes a noticeable reduction in head and efficiency, as high as 27% and 21%, respectively, and the best efficiency point with uniform inflow shifts to the point with a larger flow rate. The axial velocity of the impeller inlet in Case 2 changes more smoothly along the Span compared with that in Case 1, which further indicates a more uniform inflow at the impeller inlet. The total entropy production (TEP) of each domain in Case 1 is always higher than that in Case 2, and the TEP of the whole domain in Case 1 increased by 18.68%, 30.50%, and 29.67% with flow rates of 0.8Q_des, 1.0Q_des, and 1.2Q_des, respectively, compared with that in Case 2. In the inlet passage, the larger TEPR regions in Case 1 are mainly located in the horn passage, which is far away from the inlet side, and are also distributed in the suction side of impeller blades and guide vanes. Therefore, this work may provide an optimal design reference for pumping stations in practical application.

Sanitary centrifugal pumps are extensively used in food, pharmaceutical, and bioengineering industries due to their high cleanliness and structural compactness. However, conventional circular volutes, with constant cross-sectional area, exhibit limited diffusion capability and poor hydraulic performance. To address this, an eccentricity-based volute optimization method is proposed to develop an approximately spiral volute, which is further refined into a spiral configuration. Circular, approximately spiral, and spiral volutes were integrated into the same pump for comparative numerical analysis. Results show that, under design conditions, the approximately spiral volute increases head by 2.5 m and efficiency by 5.4%. At large flow rates, total entropy generation is reduced by 0.73 W·K ^-1 , indicating lower energy losses. Under low flow conditions, vortex structures in the blade passages and volute cross-section are effectively suppressed. The proposed eccentric optimization yields an approximately spiral volute with superior hydraulic performance and flow stability, offering theoretical support for structural optimization of sanitary centrifugal pumps.

Variable-rate irrigation (VRI) prescribes spatially differentiated water demand. A moving sprinkler implements these prescriptions through travel speed, valve duty, pressure, and timing. This review examines how model predictive control (MPC), state estimation, sprinkler hydraulics, application measurement, and digital twins can support the conversion of a prescription into verified water delivery. Evidence, classified by function and validation setting, distinguishes direct irrigation MPC studies from transferable sensing, modeling, and equipment evidence. Irrigation MPC has progressed from soil water regulation toward forecast-, risk-, crop-value-, and space-informed prescriptions. Verification of machine-level delivery combines explicit execution models with independent measurements. Field and bench studies show that motion, pressure, valve timing, nozzle geometry, footprint overlap, and wind constrain delivery and its measurement, while independent application feedback remains uncommon. The review proposes a command-to-delivery sequence comprising actuation time demand, projection onto the machine-attainable field, and separate residuals for projection, command tracking, and application transfer. A control-coupled digital twin is proposed as a testable layer preserving time alignment, model versioning, and residual provenance, and translating supported updates into feasible actions or safe degradation. The proposed future evaluation pathway comprises independently measured delivery and claim-matched ablation, with multi-season trials for interannual benefit claims and representative fault tests for resilience claims.