Search Results (98)

The aerodynamic characterization of propeller-driven UAVs is often constrained by the unfeasibility of testing the complete airframe–propeller assembly in a wind tunnel, since geometric scaling prevents simultaneous similarity of both the airframe and the propeller. To address this limitation, this work presents an integrated experimental–numerical methodology that reconstructs the full-scale free-air aerodynamic behaviour of a tractor-propeller UAV combining wind-tunnel measurements of the scaled airframe (without the propeller) and the full-scale propeller. Computational fluid dynamics (CFD) is not used to predict the full-scale UAV directly; it is used to predict differences between matched configurations, while the absolute aerodynamic level remains anchored to experiments. Dedicated CFD simulations are carried out to isolate three distinct physical contributions: scale effects, wind-tunnel blockage, and propeller installation effects. In the developed methodology, numerical simulations complement the experimental data to obtain corrected full-scale aerodynamic coefficients and propulsive maps together with a longitudinal force-equilibrium model used to determine the longitudinal force-equilibrium operating point. The reconstruction shows that scale and wind-tunnel blockage effects primarily alter the airframe aerodynamic characteristics, with a minor influence on equilibrium incidence, while propeller installation produces a substantial thrust augmentation due to airframe-induced inflow modification. Accounting for these effects leads to an overprediction of the propeller rotational speed by approximately $23\%$ when installation effects are neglected, demonstrating that the installed performance cannot be obtained by a linear superposition of isolated airframe and isolated propeller data. Full article

Small coastal crafts are often equipped with stock propellers selected from limited commercial options, without detailed matching among the hull, main engine, reduction gear, and propeller. This study presents a practical and integrated procedure for evaluating propulsion performance and designing a propeller tailored to a G/T 4.99 coastal craft under the fully loaded departure condition. The CFD resistance simulations were validated against model test measurements of resistance, sinkage, and trim and were applied over a wide range of vessel speeds. Self-propulsion simulations were subsequently conducted to evaluate the propulsive characteristics of the target vessel. Based on the evaluated self-propulsion characteristics, actual engine specifications and propeller installation data from Korean coastal vessels were used to select the main engine and reduction gear and to define practical ranges for the propeller diameter and pitch ratio. An initial propeller was determined using the $B_p-\delta$ method, after which the mean pitch ratio was iteratively corrected through full-scale performance prediction. The final propeller was selected by matching the predicted rotational speed under the trial condition to the target value determined by the engine and reduction gear while confirming the attainable vessel speed under the service condition with a 15% sea margin. The final propeller was evaluated through CFD self-propulsion simulations and compared with the stock propeller. At 16 and 18 knots, the designed propeller increased the overall propulsive efficiency by 8.4% and 10.1%, respectively, while reducing the required delivered power by 7.8% and 9.2%. These results demonstrate that the proposed procedure can improve the matching among the hull, machinery, and propeller and provide a practical basis for designing efficient propellers for small coastal crafts. Full article

In the space sector, test benches are facilities used to perform ground testing of rocket engines with solid, liquid, or hybrid propellants. These tests typically occur during the stages of development, validation, qualification, certification, and acceptance of the rocket engine assembly. Due to the periodicity and complexity related to these stages, it may be necessary to carry out several test campaigns in order to obtain the expected results. This requires skill and knowledge from the technical team involved, since the occurrence of operational nonconformities in actuator components installed in this test bench constitutes a situation with sufficient potential to put human lives at risk and/or cause material losses. In this context, this work presents a proposal for a Graphical User Interface to be integrated into the architecture of a system that performs the operational self-testing of these actuators. The virtual resources established for the windows of the Graphical User Interface are expressive and are related to the procedures defined to perform the self-testing of actuator activation, steady-state operation, and shutdown. The validation of the functionality of this Graphical User Interface is obtained through tests carried out on a prototype that was developed considering the main blocks contained in the mentioned system architecture. The satisfactory results observed in these tests suggest that the Graphical User Interface is suitable for the purpose for which it is intended. Full article

To enhance the energy efficiency of medium-sized transport vessels, one set of conventional flat rudders and three sets of twisted rudders with different twist angles were designed for a single-propeller single-rudder medium-sized transport ship. By combining model tests and computational fluid dynamics (CFD) numerical simulations, this paper systematically investigates the influence of twist angle on ship propulsion performance and energy-saving effects and reveals the corresponding energy-saving mechanism. The results show that compared with the conventional flat rudder, all three sets of twisted rudders achieve energy savings, with the main engine power reduced by approximately 1.0%. Within the research scope of this paper, the energy-saving effect improves with the increase in twist angle. Compared with the flat rudder, the installation of a twisted rudder leads to reductions in propeller thrust, torque, and rudder resistance, while the propeller’s rotational speed remains essentially unchanged. The CFD calculation results are in good agreement with the experimental data, which accurately reflect the flow field differences and explain the energy-saving mechanism. Thus, CFD can be used as an effective method for the design and optimization of twisted rudders. Full article

The in-service assessment of marine propulsion engines requires more than nominal rating comparison because operating severity is shaped by propeller demand, resistance growth, air-path response, and thermal state. This study develops a quantitative benchmarking method for the regime-dependent performance assessment of a low-speed two-stroke Wärtsilä 6RT-flex58T-D engine installed on a 31,000 DWT multi-purpose container vessel. The method integrates certified sea-trial measurements, endurance-test records, manufacturer load-diagram constraints, and a 15% service-margin projection within one reference framework. Three representative regimes are evaluated: a measured light-running baseline (SR1), a measured thermally stabilised sustained regime (SR2), and a projected heavy-running regime derived from the baseline using a 15% sea-margin assumption (R2). Comparison is performed using indicators of operating-point position, shaft torque, propeller-law consistency, selected air-path and thermal variables, load-diagram proximity, and corrected specific fuel oil consumption where available. The SR1 baseline followed the fitted propeller law with deviations not exceeding 1.18%, confirming a coherent light-running reference. In SR2, corrected SFOC decreased from 174.4 to 172.0 g/kWh, while the exhaust temperature before turbine increased from 359 °C to 435 °C, and the corresponding thermal margin decreased from 156 °C to 80 °C. Under the +15% service-margin projection, the required shaft power at the 100% trial point increased from 12,046.0 to 13,852.9 kW, exceeding the 13,560 kW installation MCR by 2.2%, with corresponding 15% increases in torque and BMEP. These results demonstrate that measured baseline operation, sustained-load severity, and projected heavy-running demand can be distinguished quantitatively within one installation-specific load-diagram-based benchmarking framework. Full article

Nowadays, most water meters are mechanical and intended to be installed on pipes completely filled with water. But the pipelines of a water supply network may contain air, which poses a metrological problem: if this air flows through the domestic intakes, it can propel the moving part of the meters, resulting in an overestimation of water consumption. By how much? There is a surprising lack of field data on this topic. So, the case of one house is reported: it is located at the top of a steep and sparsely occupied street, with water typically supplied for a few hours per day. The house’s meter (multi-jet) was estimating a huge and erratic consumption: several times more than what would be normally expected on average, and with some daily peaks exceeding the built storage capacity (underground cistern plus roof tank). After one year of monitoring, including the installation of a few devices, it is concluded that: (1) the house’s meter was affected by air in the water supply network (most likely for different reasons, of which three are discussed); (2) a small air-release valve installed just upstream from the meter did not solve the problem; (3) another mechanical meter (single-jet) installed just downstream was also affected by air (although to a lesser extent), and (4) reliable estimates of water consumption were finally obtained with an ultrasonic meter installed at the domestic intake (and with a mechanical meter installed at the roof tank’s outlet). Thus, the case reported emphasizes the need to study more how air in pipelines affects mechanical water meters and to sometimes consider alternatives for measuring domestic water consumption. Full article

Hydrodynamic Energy-Saving Devices (ESDs) have become effective solutions to improve vessel operational efficiency in maritime applications. A novel toroidal boosted appendage which is installed behind the KP505 propeller, featuring an integrated self-driving turbine and closed-loop blade structure, is proposed to simultaneously enhance propulsion efficiency, rectify wake non-uniformity, and mitigate vortex-induced energy losses. High-fidelity Computational Fluid Dynamics (CFD) simulations are conducted to evaluate the hydrodynamic performance of the device, aiming to minimize side effects such as the generated tip vortices and pressure pulses. Based on the STAR-CCM+ software, the Realizable $k-\epsilon$ turbulence model is adopted to simulate the flow fields of the propeller with and without the novel appendage. This paper focuses on investigating the influence of the new appendage on the propeller’s propulsion performance and conducts open-water performance prediction and wake field comparative analysis under different advance coefficients. The results show that the new appendage significantly improves the wake situation behind the propeller disk, changing from diffusion-flow to constriction-flow and achieving a uniform distribution of the wake field. The propulsion efficiency is increased by up to 7.453% at the design advance coefficient, and the novel toroidal boosted appendage is confirmed to have the potential to enhance the hydrodynamic performance of the propeller. Full article

For high-speed compound helicopters, such as the S-97 Raider, the reflection and diffraction effects of vertical/horizontal tails on pusher propeller noise are inevitable. To investigate the noise distortion effect of the rear-mounted pusher propeller, this study first relies on the Chinese Laboratory of Rotorcraft Navier-Stokes (CLORNS) solver, adopting the high-resolution Perturbed polynomial reconstructed Targeted Essentially Non-Oscillatory scheme (TENO-P) combined with the Delayed Detached Eddy Simulation based on the Spalart–Allmaras (SA-DDES) turbulence model to resolve the multi-scale rotor flowfield. Additionally, a continuous and conserved acoustic source extraction method is proposed to eliminate non-physical waves at the one-way Computational Fluid Dynamics and Computational AeroAcoustics (CFD–CAA) coupling interface, addressing the temporal inconsistency between flowfield evolution and acoustic propagation. Finally, numerical investigations are conducted on the instantaneous acoustic wave propagation and acoustic directivity of the pusher propeller under the influence of vertical/horizontal tails. The results show that significant acoustic distortion occurs when pusher propeller-generated noise interacts with vertical/horizontal tails. This interaction not only produces reflected and diffracted acoustic waves but also leads to wavefront discontinuities, the formation of short acoustic waves, and changes in acoustic directivity. The maximum variation in the sound pressure level reaches 10 dB at local azimuths. The distortion effect of tails on pusher propeller noise is closely correlated with the number of propeller blades. The interaction process between the propeller and tails becomes more complex with the increase in blade count, resulting in the generation of shorter acoustic waves. For the six-blade rotor, the originally continuous acoustic wave branch can be split into up to four short waves. This study confirms that the proposed Hybrid Computational AeroAcoustics (HCAA) method holds significant application prospects in the aeroacoustic research of compound helicopters. Full article

Rim-driven propellers (RDPs) have attracted renewed attention as an efficient propulsion concept for integrated electric propulsion systems, yet their structural configuration inherently limits duct geometry modification, and viscous losses associated with boundary layer separation near the duct trailing edge remain a key performance constraint. In this study, a vortex generator-based flow control strategy is proposed as a practical means of improving RDP performance without altering the duct geometry. Reynolds-averaged Navier–Stokes (RANS) simulations were conducted to examine the effects of vortex generators installed on the outer surface of the duct, with numerical reliability ensured through a grid convergence index (GCI) analysis. A steady-state multiple reference frame (MRF) approach was employed, and the resulting flow characteristics were analyzed using velocity profiles, line integral convolution (LIC) visualization, pressure field analysis, and distribution of the flow field in the wake. The results show that the vortex generators effectively delay boundary layer separation near the duct trailing edge by re-energizing the near-wall flow, thereby enhancing flow attachment and pressure recovery. Consequently, consistent improvements in thrust coefficient and propulsive efficiency are achieved over the entire range of advance ratios, while the increase in torque coefficient remains negligible. These findings demonstrate that vortex generator-based flow control offers a practical and effective approach for enhancing the open-water performance of rim-driven propellers under structural constraints. Full article

Ship propulsion performance is important for navigating. This study aims to enhance the propulsion performance of a 9500 DWT ship by integrating PBCFs into the hull–rudder–propeller–coupled system. A total of 27 PBCF models with different fin installation angles, radius ratio, and tilt angles are designed in the study. The computational fluid dynamics method is employed and a propeller open-water test is also performed to optimize the PBCF design, which is integrated into different coupled systems. The numerical results show that the PBCFs exhibit differential enhancements of propeller performance across system configurations with their efficiency changing from 4.05% to 2.87%. Moreover, the reliability of ship self-propulsion simulation is mutually validated through the combined BF (body force) and MRF (multi-reference frame) methods. Then, simulations were conducted using these two methods for the self-propulsion of a 9500 DWT ship at three different speeds. Finally, the results from using the MRF method show that the incorporation of PBCFs can reduce delivered power to propeller by 1.32% at different F_r. Full article

Small multi-rotor UAVs face endurance limitations during long-range missions due to high rotor energy consumption and limited battery capacity. This paper proposes a folding-wing range extender integrating a sliding-rotating two-degree-of-freedom folding wing—which, when deployed, quadruples the fuselage length yet folds within its profile—and a tail-thrust propeller. The device can be rapidly installed on host small multi-rotor UAVs. During cruise, it utilizes wing unloading and incoming horizontal airflow to reduce rotor power consumption, significantly extending range while minimally impacting portability, operational convenience, and maneuverability. To evaluate its performance, a 1-kg-class quadrotor test platform and matching folding-wing extender were developed. An energy consumption model was established using Blade Element Momentum Theory, followed by simulation analysis of three flight conditions. Results show that after installation, the required rotor power decreases substantially with increasing speed, while total system power growth slows noticeably. Although the added weight and drag increase low-speed power consumption, net range extension emerges near 15 m/s and intensifies with speed. Subsequent parametric sensitivity analysis and mission profile analysis indicate that weight reduction and aerodynamic optimization can effectively enhance the device’s performance. Furthermore, computational fluid dynamics (CFD) analysis confirms the effectiveness of the dihedral wing design in mitigating mutual interference between the rotor and the wing. Flight tests covering five conditions validated the extender’s effectiveness, demonstrating at 20 m/s cruise: 20% reduction in total power, 25% improvement in endurance/range, 34% lower specific power, and 52% higher equivalent lift-to-drag ratio compared to the baseline UAV. Full article

As offshore wind power continues to extend into deeper waters, the operational environment has expanded from shallow to deep seas. Self-elevating and self-propelled installation vessels have been widely adopted due to their jack-up systems and self-propulsion capabilities. The structural integrity of wind turbine installation vessels is crucial to ensure successful operations, among which the strength of the jacking frame is particularly critical. This study focuses on the bracket made of E550 steel at the root of the jacking frame. Shape optimization of the bracket was performed using parametric modeling technology, resulting in a 26% reduction in peak stress and a 12% decrease in bracket mass. Following the optimization, a full-scale fatigue test targeting local fatigue hot spots of the bracket was carried out. Based on the experimental data, the fatigue S-N curve of the bracket was obtained. Finally, a fatigue assessment was conducted on the high-stress region at the toe of the bracket. The results indicate that the bracket with unequal arm lengths exhibits lower stress concentration. Fatigue cracks of the bracket initiate at the weld toe, and the fatigue strength of the E550 steel toe joint obtained from the test is superior to that of the D-curve specified in the standards. Based on the derived S–N curve, a spectral fatigue analysis was further carried out to verify the fatigue performance of the optimized bracket. The total fatigue damage of the optimized structure over a 20-year design life was calculated as 0.6, which is below the allowable limit of 1.0, demonstrating that the optimized design satisfies the fatigue safety requirements. Full article

The search for higher efficiency in agribusiness supports the adoption of digital tools and Lean Production principles in agricultural spraying, a crucial operation for crops. Spraying is essential to ensure yield, quality, cost efficiency, and environmental protection. This study analyzed operational data from self-propelled sprayers in soybean and corn fields, classifying hours, calculating efficiencies, and applying statistical process control. Efficiencies were investigated by combining Lean Production principles with CAN-based digital monitoring, which enabled the identification of non-value-adding activities and supported the real-time management of spraying operations. The results showed that productive time accounted for 41.2% of total recorded hours, corresponding to effective operation and auxiliary tasks directly associated with the execution of spraying activities. A high proportion of unrecorded hours (21.2%) was also observed, reflecting discrepancies between administrative work schedules and machine-logged data. Additionally, coefficients of variation for operational speed and fuel consumption were 12.1% and 24.0%, respectively. Correcting special causes increased work capacity (4.9%) and reduced fuel consumption (0.9%). Economic simulations, based on efficiencies, operating parameters of the sprayer, and cost indicators, indicated that increasing scale reduces costs when installed capacity is carefully managed. Integrating telemetry with Lean Production principles enables real-time resource optimization and waste reduction. Full article

The development of green technologies in recent years in the field of wind energy conversion into electricity implies a technology transfer from the static switching field to the energy field. This paper presents a wind turbine simulator using a hardware solution following the energy conversion of a real turbine. We implemented this solution for educational and research purposes to train students in the process of electrical conversion in wind turbines. For the simulation, we chose an E82/2300 turbine, installed by ENERCON in a nearby geographical area. The turbine has the capacity to generate 2300 kW of electricity into grids. It has a direct coupling structure of the propeller to the generator. The solution is implemented on a multi-processor architecture with analog signal processing. The structure of a wind turbine is divided into three consecutive blocks, namely TUGEN, DCDC4X, and SIN3F. Each block of the simulator is designed with electronic components. The input and output signals of these blocks have similar waveforms to real signals, and their succession is interconditioned by process parameters. The innovation of the proposed solution is provided by software engineering applied to a hardware structure. The ratio between the simulated and real values is 1:60 in order to visualize the signals on a digital oscilloscope, mainly for educational purposes. Full article

Reliable prediction of tunnel thruster performance under reverse, or off-design, reverse operating direction (ROD) conditions, is crucial for modern vessels that require bidirectional thrust from a single unit—such as yachts and offshore support vessels. Despite the increasing demand for such a capability, there remains limited understanding of the unsteady hydrodynamic behavior and performance implications of ROD operation. This study addresses this gap through a scale-resolving computational fluid dynamics (CFD) investigation of a full-scale, fixed-pitch propeller with a diameter of 0.62, installed in a tunnel geometry representative of yacht-class side thrusters. Using advanced turbulence modeling, we compare the thruster’s performance under both the normal operating direction (NOD) and ROD. The results reveal notable differences: in ROD, the upstream separation zone was more compact and elongated, average thrust increases by approximately 3–4%, and torque and pressure fluctuations rise by 15–30%. These findings demonstrate that a single tunnel thruster can meet bidirectional manoeuvring requirements. However, the significantly elevated unsteady loads during ROD operation offer a plausible explanation for the increased noise and vibration frequently observed in practice. Full article