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Search Results (376)

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Keywords = thrust measurement

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18 pages, 13241 KiB  
Article
Experimental Investigation of Aerodynamic Interaction in Non-Parallel Tandem Dual-Rotor Systems for Tiltrotor UAV
by He Zhu, Yuhao Du, Hong Nie, Zhiyang Xin and Xi Geng
Drones 2025, 9(5), 374; https://doi.org/10.3390/drones9050374 - 15 May 2025
Viewed by 95
Abstract
The distributed electric tilt-rotor Unmanned Aerial Vehicle (UAV) combines the vertical take-off and landing (VTOL) capability of helicopters with the high-speed cruise performance of fixed-wing aircraft, offering a transformative solution for Urban Air Mobility (UAM). However, aerodynamic interference between rotors is a new [...] Read more.
The distributed electric tilt-rotor Unmanned Aerial Vehicle (UAV) combines the vertical take-off and landing (VTOL) capability of helicopters with the high-speed cruise performance of fixed-wing aircraft, offering a transformative solution for Urban Air Mobility (UAM). However, aerodynamic interference between rotors is a new challenge to improving their flight efficiency, especially the dynamic interactions during the transition phase of non-parallel tandem dual-rotor systems, which require in-depth investigation. This study focuses on the aerodynamic performance evolution of the tilt-rotor system during asynchronous transition processes, with an emphasis on quantifying the influence of rotor tilt angles. A customized experimental platform was developed to investigate a counter-rotating dual-rotor model with fixed axial separation. Key performance metrics, including thrust, torque, and power, were systematically measured at various tilt angles (0–90°) and rotational speeds (1500–3500 RPM). The aerodynamic coupling mechanisms between the front and rear rotor disks were analyzed. The experimental results indicate that the relative tilt angle of the dual rotors significantly affects aerodynamic interference between the rotors. In the forward tilt mode, the thrust of the aft rotor recovers when the tilt angle reaches 45°, while in the aft tilt mode, it requires a tilt angle of 75°. By optimizing the tilt configuration, the aerodynamic performance loss of the aft rotor due to rotor-to-rotor aerodynamic interference can be effectively mitigated. This study provides important insights for the aerodynamic performance optimization and transition control strategies of the distributed electric tilt-rotor UAV. Full article
(This article belongs to the Special Issue Dynamics Modeling and Conceptual Design of UAVs)
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16 pages, 3004 KiB  
Article
Experimental and Numerical Study of a UAV Propeller Printed in Clear Resin
by Mingtai Chen, Jacob Wimsatt, Tianming Liu and Tiegang Fang
Aerospace 2025, 12(5), 362; https://doi.org/10.3390/aerospace12050362 - 22 Apr 2025
Viewed by 325
Abstract
This paper presents an experimental and numerical investigation of a 254 mm resin-printed propeller operating at rotational speeds between 3000 and 9000 RPM. Propeller thrust and torque were measured using a six-degree-of-freedom load cell, while acoustic data were captured with a microphone positioned [...] Read more.
This paper presents an experimental and numerical investigation of a 254 mm resin-printed propeller operating at rotational speeds between 3000 and 9000 RPM. Propeller thrust and torque were measured using a six-degree-of-freedom load cell, while acoustic data were captured with a microphone positioned three times the propeller diameter from the center. To complement the experimental analysis, computational simulations were conducted using ANSYS Fluent with the detached eddy simulation (DES) model, the Ffowcs-Williams and Hawkings (FW-H) model, and a transient flow solver. The figure of merit (FM) results show that the resin propeller slightly outperforms two commercial counterparts with a marginal difference between the wood and resin propellers. Additionally, the resin propeller demonstrates better noise performance, exhibiting the lowest primary tonal noise, broadband noise, and overall sound pressure level (OASPL), with minimal differences between the two commercial counterparts. ANSYS Fluent simulations predict thrust and torque within a 10% error margin, showing particularly accurate results for primary tonal noise. A new trade-off index is proposed to assess the balance between propeller performance and aeroacoustics, revealing distinct trends compared to traditional metrics. Furthermore, aerodynamic phenomena such as flow separation on the leading edge near the tip, flow separation behind the middle trailing edge, and vortex interactions at the root are identified as key contributors to tonal and broadband noise. These findings provide valuable insights into propeller design and aeroacoustic optimization. Full article
(This article belongs to the Section Aeronautics)
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12 pages, 261 KiB  
Article
Is VIX a Contrarian Indicator? On the Positivity of the Conditional Sharpe Ratio
by Ehud I. Ronn and Liying Xu
Econometrics 2025, 13(2), 18; https://doi.org/10.3390/econometrics13020018 - 14 Apr 2025
Viewed by 353
Abstract
The notion of compensation for systematic risk is well ingrained in finance and constitutes the basis for numerous empirical tests. The concept an increase in systematic risk is accompanied by an increase in the required risk premium has strong intuitive content: The more [...] Read more.
The notion of compensation for systematic risk is well ingrained in finance and constitutes the basis for numerous empirical tests. The concept an increase in systematic risk is accompanied by an increase in the required risk premium has strong intuitive content: The more risk there is to be borne, the greater the compensation therefor. In recognizing previous research on the ex ante and ex post reward to risk, the thrust of this paper is to augment those previous tests of expected and realized returns by providing several distinct empirical tests of the proposition the market rewards the undertaking of systematic equity risk, the latter as measured by the VIX volatility index. Thus, in this paper’s empirical section, we use several empirical approaches to answer the question, Using realized returns, is an increase in systematic risk VIX accompanied by an increase in the equity risk premium? While the empirical results are not always statistically significant, our answer is in the affirmative. Full article
19 pages, 3648 KiB  
Article
Design of an Experimental Test Rig for Shrouded and Open Rotors for Small Rotary Wing Unmanned Aerial System
by Abdallah Dayhoum, Alejandro Ramirez-Serrano and Robert J. Martinuzzi
Electronics 2025, 14(8), 1584; https://doi.org/10.3390/electronics14081584 - 14 Apr 2025
Viewed by 259
Abstract
This study details the design and testing of a custom test rig for evaluating the performance of both open and shrouded rotors. The rig includes a two-axis load cell that is directly connected to the rotor to measure the rotor thrust separated from [...] Read more.
This study details the design and testing of a custom test rig for evaluating the performance of both open and shrouded rotors. The rig includes a two-axis load cell that is directly connected to the rotor to measure the rotor thrust separated from the total thrust when testing shrouded rotors and ensure accurate torque measurements, independent of external structural influences. Moreover, a main load cell is used to measure the total thrust for both configurations (open and shrouded rotor), as it is connected to the entire setup. Rotor RPM is monitored by capturing the voltage frequency from the BLDC motor, controlled using a Pololu Maestro Controller through the electronic speed controller. A shunt resistance is used to calculate the current through the electric Brushless Direct Current (BLDC) motor and by measuring the voltage, the electric power is calculated. By combining both mechanical and electrical power measurements, the BLDC motor’s efficiency is calculated. Automated data collection is conducted using National Instruments DAQ systems, with averaged measurements of thrust, torque, RPM, current, and voltage. Two rotors are tested to obtain performance data for both open and shrouded configurations. Additionally, a computational study is carried out to account for the aerodynamic effects of the rig’s structural elements. Uncertainty analysis is employed to assess the reliability of the experimental results by quantifying the numerical errors associated with both random and systematic errors encountered during the rotor’s performance evaluation. Full article
(This article belongs to the Special Issue Recent Advances in Robotics and Automation Systems)
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17 pages, 2285 KiB  
Article
Assessing the Metrological Reliability of Static Firing Tests of Rocket Motors Through the Evaluation of Thrust and Total Impulse Measurement Uncertainty
by Fernando de Paula Leite Castor, Carlos Roberto Hall Barbosa and Elcio Cruz de Oliveira
Appl. Sci. 2025, 15(8), 4280; https://doi.org/10.3390/app15084280 - 13 Apr 2025
Viewed by 284
Abstract
A solid propellant rocket motor is a propulsion system used in missiles and rockets that burns a propellant, typically composed of a mixture of fuel and an oxidizer, to generate the thrust necessary to propel the vehicle. During both the development and quality [...] Read more.
A solid propellant rocket motor is a propulsion system used in missiles and rockets that burns a propellant, typically composed of a mixture of fuel and an oxidizer, to generate the thrust necessary to propel the vehicle. During both the development and quality assurance phases, static firing tests of rocket motors are conducted to verify whether the system requirements meet the product specifications. These tests aim to produce two main types of graphs, “thrust versus burn time” and “pressure versus burn time,” both generated by the rocket motor during the burn. While thrust and pressure are important parameters in the design of a rocket motor, total impulse is the quantity that incorporates the crucial element of time, measuring how high a rocket can be launched. To ensure greater metrological reliability in static tests of rocket motors, it is important to carefully evaluate the uncertainty levels in the measurement chain of the data acquisition system. This work aims to assess the uncertainty levels expressed in the calculated total impulse values during a static firing test of a rocket motor at the Propulsion Jets Testing Laboratory of the Brazilian Army Technological Center. To estimate the measurement uncertainty of the chain in question, approaches based on combined and expanded uncertainty theories were adopted. These methodologies consider Type A and Type B uncertainties, providing a comprehensive and rigorous analysis. In addition to the uncertainties previously mentioned, the oscillation of the measured signal should also be recognized as a contributing factor to the overall uncertainty in the calculation of total impulse. By incorporating these various sources of uncertainty, we can achieve a more comprehensive and reliable understanding of the uncertainty associated with the measurements obtained from the measurement chain. This analysis yields a measurement uncertainty of 0.24% for thrust and 0.007% for impulse, both calculated at a confidence level of 95.45%. Full article
(This article belongs to the Section Aerospace Science and Engineering)
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14 pages, 3941 KiB  
Article
Modelling and Experimental Testing of Passive Magnetic Bearings for Power Loss Reduction
by Alessandro Vigliani, Salvatore Paolo Cavallaro and Simone Venturini
Appl. Sci. 2025, 15(8), 4149; https://doi.org/10.3390/app15084149 - 9 Apr 2025
Viewed by 227
Abstract
The development of rotordynamic systems with reduced energy dissipation is a key challenge in modern applications, such as Flywheel Energy Storage Systems. This paper investigates a fully passive vertical rotor system supported by two passive magnetic bearings whose configuration provides radial stability while [...] Read more.
The development of rotordynamic systems with reduced energy dissipation is a key challenge in modern applications, such as Flywheel Energy Storage Systems. This paper investigates a fully passive vertical rotor system supported by two passive magnetic bearings whose configuration provides radial stability while minimising power losses due to their thrust effect. A numerical model describes the forces and stiffness of the magnetic bearings, identifying the operational range of the thrust–radial support configuration. A test rig is developed for the experimental characterisation of the rotor and passive magnetic bearings in both static and dynamic conditions. Different magnetic thrust force levels are tested by varying the axial distance between the rotor and stator magnetic rings of the bearings. Static tests are performed to measure the weight force compensation corresponding to the different bearing configurations, validating the numerical model. Dynamic tests analyse the rotor power losses with a non-invasive approach via optical sensor measurements. Full article
(This article belongs to the Special Issue Rotor Dynamics: Research and Applications)
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12 pages, 933 KiB  
Review
Elderly Hip Osteoarthritis: A Review of Short-Term Pain Relief Through Non-Weight-Bearing Therapies
by Olivia Norato, Sarah Velez, Arbonor Lleshi, Gordon Lam, Marlon Morales, Glory Udechi, Edwin Cung and Jean-Philippe Berteau
J. Funct. Morphol. Kinesiol. 2025, 10(2), 124; https://doi.org/10.3390/jfmk10020124 - 8 Apr 2025
Viewed by 518
Abstract
Older individuals with hip osteoarthritis (OA) who have difficulty walking, climbing stairs, or performing daily tasks often find non-weight-bearing (NWB) exercises essential for rebuilding strength and preserving function without further stressing the joints. In addition, those with a higher body mass index (BMI) [...] Read more.
Older individuals with hip osteoarthritis (OA) who have difficulty walking, climbing stairs, or performing daily tasks often find non-weight-bearing (NWB) exercises essential for rebuilding strength and preserving function without further stressing the joints. In addition, those with a higher body mass index (BMI) particularly benefit from NWB therapy, as it alleviates joint pressure while facilitating safe and effective rehabilitation. Thus, NWB interventions, such as manual therapy (MT) and aquatic therapy (AT), are especially critical for older adults aged 60 and above, offering pain relief and functional improvement by minimizing gravitational impact on the hip joint. This review examines the effectiveness of these approaches in managing hip OA symptoms and decreasing pain. The inclusion criteria for the study consisted of randomized controlled trials or controlled trials focused on adult patients with primary osteoarthritis of the hip joint, utilizing interventions such as MT (including thrust joint mobilizations, non-thrust/oscillatory mobilizations, and soft tissue mobilization) or AT (including hydrotherapy and water therapy), and assessing outcomes related to pain. We selected nine studies that included a total of n = 1037 individuals. It evaluated outcomes such as self-reported pain levels using measures like the Western Ontario and McMaster Universities Osteoarthritis (WOMAC), Numeric Rating Scale (NRS), and Visual Analog Scale (VAS). Beyond statistical differences, both therapies were evaluated for Minimal Clinically Important Difference (MCID). While MT studies indicated a decrease in pain according to pain index scores, they showed short-term effectiveness till five weeks but lacked sustained clinical efficacy beyond this period. AT showed positive results within a ten-week period, although its effectiveness seemed to level off beyond this duration, falling below the threshold of clinical efficiency. After 10 weeks of treatment, there is no discernible clinical benefit in terms of pain reduction. Both interventions without gravitational impact seem suitable for providing short-term pain relief for primary hip osteoarthritis patients, but long-term pain relief—meaning after ten weeks—should be maintained through therapeutic exercise and patient education. Full article
(This article belongs to the Section Physical Exercise for Health Promotion)
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24 pages, 5207 KiB  
Article
Finite-Time Formation Control for Clustered UAVs with Obstacle Avoidance Inspired by Pigeon Hierarchical Behavior
by Zhaoyu Zhang, Yang Yuan and Haibin Duan
Drones 2025, 9(4), 276; https://doi.org/10.3390/drones9040276 - 4 Apr 2025
Viewed by 330
Abstract
To address the formation control issue of multiple unmanned aerial vehicles (UAVs), a finite-time control scheme based on terminal sliding mode (TSM) is investigated in this paper. A quadcopter UAV with the vertical takeoff property is considered, with cascaded kinematics composed of rotational [...] Read more.
To address the formation control issue of multiple unmanned aerial vehicles (UAVs), a finite-time control scheme based on terminal sliding mode (TSM) is investigated in this paper. A quadcopter UAV with the vertical takeoff property is considered, with cascaded kinematics composed of rotational and translational loops. To strengthen the application in the low-cost UAV system, the applied torque is synthesized with an auxiliary rotational system, which can avoid utilizing direct attitude measurement. Furthermore, a terminal sliding mode surface is established and employed in the finite-time formation control protocol (FTFCP) as the driven thrust of multiple UAVs over an undirected topology in the translational system. To maintain the safe flight of the UAV clusters in an environment to avoid collision with obstacles or with other UAV neighbors, a pigeon-hierarchy-inspired obstacle avoidance protocol (PHOAP) is proposed. By imitating the interactive hierarchy that exists among the homing pigeon flocks, the collision avoidance scheme is separately enhanced to generate the repulsive potential field for the leader maneuver target and the follower UAV cluster. Subsequently, the collision avoidance laws based on pigeon homing behavior are combined with the finite-time sliding mode formation protocol, and the applied torque is attached as a cascaded structure in the attitude loop to synthesize an obstacle avoidance cooperative control framework. Finally, simulation scenarios of multiple UAVs to reach a desired formation among obstacles is investigated, and the effectiveness of the proposed approach is validated. Full article
(This article belongs to the Special Issue Biological UAV Swarm Control)
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16 pages, 5590 KiB  
Article
Experimental and Computational Study of the Aerodynamic Characteristics of a Darrieus Rotor with Asymmetrical Blades to Increase Turbine Efficiency Under Low Wind Velocity Conditions
by Muhtar Isataev, Rustem Manatbayev, Zhanibek Seydulla, Nurdaulet Kalassov, Ainagul Yershina and Zhandos Baizhuma
Appl. Syst. Innov. 2025, 8(2), 49; https://doi.org/10.3390/asi8020049 - 3 Apr 2025
Viewed by 471
Abstract
In this study, we conducted experimental and numerical investigations of a Darrieus rotor with asymmetrical blades, which has two structural configurations—with and without horizontal parallel plates. Experimental tests were conducted in a wind tunnel at various air flow velocities (ranging from 3 m/s [...] Read more.
In this study, we conducted experimental and numerical investigations of a Darrieus rotor with asymmetrical blades, which has two structural configurations—with and without horizontal parallel plates. Experimental tests were conducted in a wind tunnel at various air flow velocities (ranging from 3 m/s to 15 m/s), measuring rotor rotation frequency, torque, and thrust force. The computational simulation used the ANSYS 2022 R2 Fluent software package, where CFD simulations of air flow around both rotor configurations were performed. The calculations employed the Realizable k-ε turbulence model, while an unstructured mesh with local refinement in the blade–flow interaction zones was used for grid generation. The study results showed that the rotor with horizontal parallel plates exhibits higher aerodynamic efficiency at low wind velocities compared to the no-plates rotor. The experimental findings indicated that at wind speeds of 3–6 m/s, the rotor with plates demonstrates 18–22% higher torque, which facilitates the self-start process and stabilizes turbine operation. The numerical simulations confirmed that horizontal plates contribute to stabilizing the air flow by reducing the intensity of vortex structures behind the blades, thereby decreasing aerodynamic drag and minimizing energy losses. It was also found that the presence of plates creates a directed flow effect, increasing the lift force on the blades and improving the power coefficient (Cp). In the case of the rotor without plates, the CFD simulations identified significant low-pressure zones and high turbulence regions behind the blades, leading to increased aerodynamic losses and reduced efficiency. Thus, the experimental and numerical modeling results confirm that the Darrieus rotor with horizontal parallel plates is a more efficient solution for operation under low and variable wind conditions. The optimized design with plates ensures more stable flow, reduces energy losses, and increases the turbine’s power coefficient. These findings may be useful for designing small-scale wind energy systems intended for areas with low wind speeds. Full article
(This article belongs to the Special Issue Wind Energy and Wind Turbine System)
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22 pages, 5174 KiB  
Article
In Situ Measurement and Mapping of Lubricant Film Temperature in Cylindrical Roller Thrust Bearings Using Thin-Film Sensors
by Manjunath Manjunath, Patrick De Baets and Dieter Fauconnier
Machines 2025, 13(4), 297; https://doi.org/10.3390/machines13040297 - 2 Apr 2025
Viewed by 234
Abstract
This study explores the in situ measurement of contact temperature in thermo-elastohydrodynamic lubrication (TEHL) within cylindrical roller thrust bearings (CRTBs) utilizing vapour-deposited resistive thin-film sensors. The sensors, optimized for compactness and high spatial resolution, were strategically embedded on the stationary bearing raceways near [...] Read more.
This study explores the in situ measurement of contact temperature in thermo-elastohydrodynamic lubrication (TEHL) within cylindrical roller thrust bearings (CRTBs) utilizing vapour-deposited resistive thin-film sensors. The sensors, optimized for compactness and high spatial resolution, were strategically embedded on the stationary bearing raceways near the outer, inner, and mean radius. This configuration enabled a precise measurement of temperature variations in both pure rolling and rolling–sliding regions of the CRTBs. The experimental results revealed a consistent decrease in temperature from the inner and outer radius zones towards the mean radius as the slip-to-roll ratio (SRR) decreased in these regions. Temperature profiles showed an early rise in the inlet zone attributed to thermal inlet shear. At higher speeds, a secondary temperature peak indicative of full-film lubrication was observed in the outlet zone immediately following the Hertzian contact. The study further shows the influence of surface pressure, shear rates, sliding friction, and circumferential speed on contact temperature dynamics, offering insights into their complex interplay. Additionally, viscosity variations due to different oil temperatures were found to critically affect the rate of temperature rise and the propensity for mixed friction phenomena. A higher viscosity resulted in an earlier onset of the temperature rise in the contact, while a lower viscosity and higher speeds promote mixed lubrication, leading to reduced contact film temperatures. These findings provide valuable insights into the behaviour of CRTB-lubricated contacts under various operating conditions and serve as crucial validation data for advanced TEHL computational models. Full article
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9 pages, 4387 KiB  
Proceeding Paper
Designing and Testing of HDPE–N2O Hybrid Rocket Engine
by Triyan Pal Arora, Noah Buttrey, Peter Kirman, Sanmukh Khadtare, Eeshaan Kamath, Dario del Gatto and Adriano Isoldi
Eng. Proc. 2025, 90(1), 34; https://doi.org/10.3390/engproc2025090034 - 13 Mar 2025
Viewed by 307
Abstract
Hybrid Rocket Engines (HREs) combine the advantages of solid and liquid propellants, offering thrust control, simplicity, safety, and cost efficiency. Part of the research on this rocket architecture focuses on optimising combustion chamber design to enhance performance, a process traditionally reliant on time-consuming [...] Read more.
Hybrid Rocket Engines (HREs) combine the advantages of solid and liquid propellants, offering thrust control, simplicity, safety, and cost efficiency. Part of the research on this rocket architecture focuses on optimising combustion chamber design to enhance performance, a process traditionally reliant on time-consuming experimental adjustments to chamber lengths. In this study, two configurations of HREs were designed and tested. The tests aimed to study the impact of post-chamber lengths on rocket engine performance by experimental firings on a laid-back test engine. This study focused on designing, manufacturing, and testing a laid-back hybrid engine with two chamber configurations. The engine features a small combustion chamber, an L-shaped mount, a spark ignition, and nitrogen purging. Data acquisition includes thermocouples, pressure transducers, and a load cell for thrust measurement. Our experimental findings provide insights into thrust, temperature gradients, pressure, and plume characteristics. A non-linear regression model derived from the experimental data established an empirical relationship between performance and chamber lengths, offering a foundation for further combustion flow studies. The post-chamber length positively impacted the engine thrust performance by 2.7%. Conversely, the pre-chamber length negatively impacted the performance by 1.3%. Further data collection could assist in refining the empirical relation and identifying key threshold values. Full article
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20 pages, 19578 KiB  
Article
Design of High-Efficiency Jet Lift Enhancement for Flaps Under Propeller Slipstream Influence
by Yan Shao, Wanbo Wang, Jiao Sun, Wenyi Chen, Xinhai Zhao and Jiaxin Pan
Aerospace 2025, 12(3), 232; https://doi.org/10.3390/aerospace12030232 - 13 Mar 2025
Viewed by 449
Abstract
Both propeller slipstream and flap jet flow can significantly increase the aircraft lift coefficient. To establish design principles for efficient lift enhancement via jet flow under the influence of slipstream, wind tunnel experiments are conducted on a wing with propeller slipstream and jet [...] Read more.
Both propeller slipstream and flap jet flow can significantly increase the aircraft lift coefficient. To establish design principles for efficient lift enhancement via jet flow under the influence of slipstream, wind tunnel experiments are conducted on a wing with propeller slipstream and jet flow. Force measurements using a balance and flow field measurements using hot-wire anemometry are employed to investigate the effects of different jet flow distribution methods on lift enhancement. The results indicate that the coupling of slipstream and jet flow effects can significantly increase wing lift. The stronger the slipstream effect, the more pronounced the lift enhancement under the same momentum coefficient. At the same thrust coefficient, a higher momentum coefficient is required in the slipstream-affected region to suppress airflow separation. Under the same jet flow rate, increasing the momentum coefficient in the slipstream-affected region can significantly improve lift enhancement. At the thrust coefficient of 0.46 and the momentum coefficient of 0.1, the optimized jet flow distribution method achieved a 52.6% greater lift enhancement compared to the spanwise uniform jet flow distribution method. Full article
(This article belongs to the Section Aeronautics)
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28 pages, 38281 KiB  
Article
Numerical Investigation of the Impact of Processing Conditions on Burr Formation in Carbon Fiber-Reinforced Plastic (CFRP) Drilling with Multiscale Modeling
by Guangjian Bi, Xiaonan Wang, Yongjun Shi, Cheng Zhang and Xuejin Zhao
Materials 2025, 18(6), 1244; https://doi.org/10.3390/ma18061244 - 11 Mar 2025
Viewed by 447
Abstract
Burrs generated during the drilling of carbon fiber-reinforced plastics (CFRPs) would seriously reduce the service life of the components, potentially leading to assembly errors and part rejection. To solve this issue, this paper proposed a finite element (FE) model with multiscale modeling to [...] Read more.
Burrs generated during the drilling of carbon fiber-reinforced plastics (CFRPs) would seriously reduce the service life of the components, potentially leading to assembly errors and part rejection. To solve this issue, this paper proposed a finite element (FE) model with multiscale modeling to investigate the formation and distribution of burrs at various processing conditions. The FE model comprised the microscopic fiber and resin phases to predict the formation process of burrs, while part of the CFRP layers was defined to be macroscopic equivalent homogeneous material (EHM) to improve the computational efficiency. A progressive damage constitutive model was proposed to simulate the different failure modes and damage propagation of fibers. The impact of strain rate on the mechanical properties of the resin and CFRP layers was considered during the formulation of their constitutive models. With this numerical model, the formation process of the burrs and the drilling thrust force were accurately predicted compared to the experimental measurements. Then, the burr distributions were analyzed, and the influences of the drill bit structures and drilling parameters on burrs were assessed. It was concluded that the burrs were easily generated in the zones with 0° to 90° fiber cutting angles at the drilling exit. The sawtooth structure could exert an upward cutting effect on burrs during the downward feed of the tool; thus, it is helpful for the inhibition of burrs. More burrs were produced with higher feed rates and reduced spindle speeds. Full article
(This article belongs to the Special Issue Advanced Computational Methods in Manufacturing Processes)
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19 pages, 2550 KiB  
Article
Analytical Modeling of Shrouded Rotors in Hover with Experimental and Computational Validation
by Abdallah Dayhoum, Alejandro Ramirez-Serrano and Robert J. Martinuzzi
Actuators 2025, 14(3), 138; https://doi.org/10.3390/act14030138 - 11 Mar 2025
Cited by 1 | Viewed by 660
Abstract
Rotors have been utilized for aircraft propulsion since the dawn of aviation, but their performance can degrade significantly if not properly designed. This study focuses on developing an accurate design tool and model validation for shrouded rotors. An experimental test rig was designed [...] Read more.
Rotors have been utilized for aircraft propulsion since the dawn of aviation, but their performance can degrade significantly if not properly designed. This study focuses on developing an accurate design tool and model validation for shrouded rotors. An experimental test rig was designed and manufactured to measure the rotor thrust and total thrust separately as well as the rotor torque. A key aspect was to account for the impact of a test rig on experimental results using computational simulations for the shrouded rotor configuration with and without the test rig. The findings indicate that the effects of the test rig were minimal and could be neglected, ensuring the validity of the experimental data compared to the analytical model. The analytical model employs a hybrid approach combining blade element momentum theory (BEMT) and the sphere-cap model which are used in conjunction with the shrouded rotor inflow ratio, as well as post-stall and tip gap clearance models. BEMT is used to calculate rotor performance, while the sphere-cap model addresses the aerodynamic influence of the shroud. The results demonstrate that the analytical model predicts shrouded rotor performance with considerable accuracy, addressing both the rotor dynamics and the shroud’s contribution to performance. Full article
(This article belongs to the Special Issue Aerospace Mechanisms and Actuation—Second Edition)
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13 pages, 5387 KiB  
Article
Thrust Measurement of an Integrated Multi-Sensor Micro-Newton Cold Gas Thruster
by Songcai Lu, Yong Gao, Haibo Tu, Xudong Wang, Xinju Fu, Gang Meng, Jun Long, Xuhui Liu and Yong Li
Aerospace 2025, 12(3), 210; https://doi.org/10.3390/aerospace12030210 - 6 Mar 2025
Viewed by 1994
Abstract
In recent years, cold gas thrusters have been successfully deployed in numerous missions, showcasing their exceptional reliability and enabling ultra-precise space operations across a broad thrust range. This article introduces an integrated cold gas thruster that integrates flow, pressure, and displacement sensors. The [...] Read more.
In recent years, cold gas thrusters have been successfully deployed in numerous missions, showcasing their exceptional reliability and enabling ultra-precise space operations across a broad thrust range. This article introduces an integrated cold gas thruster that integrates flow, pressure, and displacement sensors. The thrust range of this thruster can exceed 1000 μN at most, and the resolution can reach up to 0.1 μN at low thrust. The results of the high-precision displacement sensor are good, showing that the thruster performs well in terms of flow control accuracy and thrust output sensitivity. The measurement accuracy of the force frame itself is also excellent, and it can detect small thrust changes of 0.1 μN. The thrust noise level of the thruster is good, comparable to the standard noise levels of the experimental environment. Full article
(This article belongs to the Section Aeronautics)
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