CFD-based optimization of a modified split-type reaction water turbine using response surface methodology

CFD-based investigation of blade thickness ratio effects on pico-hydro crossflow turbine performance

Indonesia’s vast hydropower potential remains significantly untapped, despite the relevance of low-head water resources for decentralised rural electrification. This study investigates the effect of the blade thickness ratio (L/H) of a centre-convex upper blade profile on the hydraulic performance of a pico-hydro crossflow turbine. The novelty of this work lies in isolating L/H as a manufacturable blade-profile variable and linking its influence to velocity-triangle design, transient CFD results, benchmark comparison, and flow-field mechanisms. The numerical model was assessed through mesh independence, time-step independence, analytical benchmark comparison, and comparison with relevant literature. The reported efficiency is therefore interpreted as runner-domain hydraulic efficiency rather than complete electro-mechanical system efficiency. The optimum L/H ratio of 0.5 achieved 81.80% hydraulic efficiency and 210.07 W mechanical power at 600 rpm under a 3 m head. This performance is associated with a favourable pressure difference, smoother streamlines, and delayed separation, whereas the thickest blade (L/H of 1.5) produced stronger blockage, recirculation, and efficiency reduction to 56.31%. The results provide design guidance for locally manufacturable pico-hydro crossflow turbines and establish a basis for future prototype validation and field installation in remote Indonesian communities.

Improved Performance of Waterfall Hydraulic Cross-Flow Turbines with and Without Guide Wall

The improved performance of a waterfall cross-flow hydraulic turbine was investigated through combined experimental and numerical analyses to elucidate the effects of key design parameters, including tip-speed ratio, number of blades, and off-axis distance. Additionally, the influence of a circular guide wall on the performance of cross-flow turbine was investigated by installing it along the runner. The numbers of blades studied were 8, 12, 16, 24, and 32, and efficiency contours were evaluated for various combinations of off-axis distances and tip-speed ratios. Peak efficiency of the turbine increased with the number of blades, reaching 70% at 32 blades. Correspondingly, the optimum off-axis distance shifted from 0.35 to 0.48, approaching the blade edge with a minor change in tip-speed ratio from 0.7 to 0.6. The improved efficiency stems from local torque caused by flow across the entire blade due to an appropriate inflow angle at large off-axis distances, where a high blade count suppresses leakage flow as observed in the flow-field visualization. Furthermore, the results of the guide-wall study showed that the efficiency of the cross-flow turbine with a lower number of blades increased when using a circular guide wall along the runner. This was due to the suppression of leakage flow on the blades, even with fewer blades. However, the influence of the guide wall became saturated with an increasing number of blades, approaching the efficiency without a guide wall. The efficiency of the waterfall cross-flow hydraulic turbine after optimization was improved and approached that of a closed-type cross-flow hydraulic turbine, while the feature of easy and low-cost maintenance was retained.

SURFACE ROUGHNESS INFLUENCE ON THE HYDRAULIC PERFORMANCE OF AN API 610 BB3 MULTISTAGE CENTRIFUGAL PUMP: AN EXPERIMENTAL–CFD STUDY

Surface roughness affects the hydraulic performance and energy efficiency of API 610 BB3 (between-bearings, axially split, multistage) pumps used in oil, gas, and petrochemical service. We quantify its impact using experiments and computational fluid dynamics (CFD). A four-stage pump was tested at 2900 rpm on a closed-loop rig, and head–flow-rate (Q–Hm) and efficiency–flow-rate (Q–η) characteristics were measured over 30–90 m³/h. Surface roughness of the main hydraulic components was measured using a profilometer and represented in the numerical model by equivalent sand-grain roughness values ks = 0, 25, 50, and 73 µm applied to all wetted walls. Three-dimensional Reynolds-averaged Navier–Stokes (RANS) simulations were performed using the SST k–ω turbulence model with rough-wall functions on a domain including leakage and return channels. The ks = 73 µm case agrees with the measured curves, with the efficiency deviation limited to ~4.1% within 45–90 m³/h, whereas larger deviations occur at 30 m³/h due to part-load operation. Near the best-efficiency region, increasing ks from 0 to 73 µm reduces head by 5.94% and efficiency by 6.62 percentage points. Neglecting roughness overestimates performance; realistic roughness is required for CFD-based prediction of API 610 BB3 pumps.

Experimental optimization and modeling of Pelton turbine performance with emphasis on energy and exergy efficiency

Influence of Structural Parameters on Airflow Uniformity and Optimisation of a Tower-type Air-assisted Sprayer Based on Computational Fluid Dynamics

In air-assisted orchard spraying, airflow characteristics strongly determine spray performance. This study designed a tower-shaped fan for grape canopies and investigated its aerodynamic behaviour. A three-dimensional computational fluid dynamics (CFD) model of the internal flow field was established to quantify the effects of shroud taper, upper and lower guide-vane angles, inlet diameter, and inlet position on outlet air-velocity uniformity. Single-factor simulations confirmed that all selected structural parameters significantly affect the outlet air velocity’s coefficient of variation (CV). Based on these results, central composite design was applied for multi-parameter optimisation. A second-order regression model was developed to describe the relationship between guide-vane angles, shroud taper, inlet position, inlet diameter, and air-velocity CV response. Analysis of variance showed that the influence of the factors decreased in the following order: guide-vane angle > inlet position > inlet diameter > shroud taper. Numerical optimisation identified the optimal configuration as a guide-vane angle of 118.37°, shroud taper of 23.84°, inlet position of 29.35 mm, and inlet diameter of 493.92 mm. Under these conditions, the predicted air-velocity CV decreased to 12.07%. A field validation experiment was conducted using representative measurement points selected from the simulated velocity distribution. The maximum relative error between measured and simulated values was below 6%, indicating strong agreement. These results confirm the reliability of the CFD model and demonstrate its effectiveness for structural optimisation of orchard air-assisted spraying equipment.

Validated DEM-CFD Modeling of Torque Draw and Distribution in a HIGmill

Vertical stirred mills are increasingly used for fine and ultrafine grinding in the mineral processing industry due to their high energy efficiency. Accurate prediction of energy consumption and its distribution within the mill is therefore critical for equipment design, optimization and aftermarket services, as demonstrated by existing analytical models. In this study, torque distribution along the mill shaft is quantified for various rotor configurations using DEM, with systematic variation of rotor diameter, spacing and alignment. Furthermore, a coupled DEM–CFD approach is employed to model torque and power draw under different operating conditions, including shaft speed, flow rate and filling level. The results quantify the influence of these operating parameters and are validated against measurements from a sensor-equipped water-fluidized test mill, demonstrating that a one-way coupled DEM–CFD model reproduces system behavior with high fidelity (NRMSE < 3% for power draw). Additionally, comparison between DEM and DEM–CFD results highlight the importance of hydrodynamic effects in stirred milling.