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Increased ship traffic due to climate change increases underwater noise in the Arctic. Therefore, accurate measurements of underwater radiated noise are necessary to map marine sound and quantify shipping's impact on the Arctic ecosystem. This paper presents a method to calculate opportunistic source levels (SLs) using passive acoustic data collected at six locations in the Western Canadian Arctic from 2018 to 2022. Based on Automatic Identification System data, acoustic data, and a hybrid sound propagation model, the SLs of individual ships were calculated within a 5 km radius of each measurement site. A total of 66 measurements were obtained from 11 unique vessels, with multiple measurements from the same vessel type contributing more SLs. For vessels with propeller cavitation, measured SLs correlated positively with vessel parameters, such as speed and length. SL and speed did not correlate well for vessels without propeller cavitation. The JOMOPANS-ECHO SL model produced good agreement with measured SL for certain ship types (container ships, a tanker, and a passenger vessel). However, significant differences between measurement and model are evident for certain polar-class ships that travel in the Arctic, indicating that more controlled SL measurements are needed. [ABSTRACT FROM AUTHOR]

This paper presents an analysis of the acceleration of a fast boat using a simulation model. Mathematical equations of ship motion dynamics with two types of propeller capabilities are developed using MATLAB and Simulink as simulation tools. The equations are extended to include the acting thrust, resistance, propeller's performance curves, and the PID governor curve for the acceleration manoeuvre. The application models the dynamic differential equations representing the vessel dynamics in one degree of freedom. MATLAB code was used to develop the ship acceleration as a multibody system. Modules of hydrodynamic forces, resistance, moments, and propeller performances were implemented to simulate the ship manoeuvring process. A comparison of the results for the boat's propulsion performance with two different propellers and the characteristics of the PID governor, which controls the fuel dose in the gas turbines, was carried out. We present a summary including a comparative analysis of the results for the boat dynamics with and without the PID governor. The results obtained here confirm significant discrepancies between the results of numerical simulations with and without the PID governor. [ABSTRACT FROM AUTHOR]

In the process of designing a marine propeller, hydroelasticity effects are neglected in most cases, due to the negligible influence of the blade's deformation on its hydrodynamic characteristics. However, there are cases where the impact of hydroelasticity is crucial, for example in the case of high skew-back propellers or heavy-loaded composite propellers. Furthermore, the importance of composite propellers is growing due to their wide range of application, for instance in naval ships and unmanned vehicles. Although structural models and two-way fluid-structure interactions are implemented in most commercial CFD solvers, their relevance to the design process is severely limited due to the high computational cost for a single iteration. An effective solution would therefore be to implement a two-way fluid-structure interaction model in the lifting surface software, which is commonly accepted as a design tool due to its relatively low computational time and its applicability to multi-criteria optimisation. This paper presents the results of hydrodynamic analyses of an elastic propeller carried out using in-house software based on the lifting surface flow model, and extended with the FEM model for the blade structure. The results are compared with experimental measurements and computational analyses with the commercial RANS solver STAR-CCM+. [ABSTRACT FROM AUTHOR]

This paper presents an investigation of the scale effect on the flow around a propeller using the CFD method. The differences in the numerical setup and the results obtained for the characteristics of an open water propeller are described and analysed in this paper. Moreover, the paper also highlight and analyse the scale effect on differences in flow around the propeller, such as the pressure fields in the cross section, the distributions of the skin friction coefficient and limiting streamlines on the propeller blade, the vortices in the wake of the propeller, and the velocity fields. The differences in the flow around the propeller are more clearly seen when it works under heavy loading conditions, an important finding that can support designers in improving propeller performance, investigating cavitations, etc. at the full scale. The reference propeller used in this study is the benchmark propeller PPTC VP 1304. [ABSTRACT FROM AUTHOR]

Propeller cavitation is one of the main causes of pressure fluctuation and noise around marine propellers, and tip vortex cavitation is one of the main causes of high-frequency underwater radiated noise. To predict tip vortex cavitation, it is necessary to correctly describe the radius of the vortex core and the vortex circulation of the tip vortex. Therefore, in this study, non-cavitating flow field measurements around the tip of model propellers were made for the 0.75 m diameter working section of the large cavitation tunnel at the National Maritime Research Institute, Japan (NMRI) using 2D-PIV. Identification procedures were investigated to develop a tip vortex model. The vortex properties (radius of vortex core and vortex circulation) of the tip vortex were obtained by applying by a Rankine vortex model and a Burgers vortex model. The measured velocity and vorticity values around the tip vortex as identified by the Burgers vortex model were in better agreement than those given by the Rankine vortex model. The Burgers vortex model was suitable for obtaining vortex properties from the measured flow field around the tip vortex. The vortex properties obtained from the identification using the Burgers vortex model showed the Reynolds number demonstrated a greater effect on the radius of the vortex core and vortex circulation. The higher the Reynolds numbers, the smaller the radius of the vortex core and the smaller vortex circulation tends to be. It is also shown that this Reynolds number effect differs depending on the blade shape of the propellers. [ABSTRACT FROM AUTHOR]

The aim of the paper is the prediction of noise generated by the propeller, hydrodynamic performance and the structural behavior of the marine propeller using two-way fluid–structure interaction (FSI) method at advanced velocities of 6, 8, 10, 12 and 14 Knots. ANSYS-Workbench software is used to establish the coupling between the fluid flow and structural solver. The computed hydrodynamic performance parameters of DTMB 4119 propeller at different advanced velocities and Sound Pressure Level (SPL) at advance coefficient of 0.833 are compared with the data available in the literature and found close agreement. The validated computational methodology is applied for the two-way FSI analysis of the marine propeller. Ffowcs William's–Hawkings (FW–H) model is used to predict the noise spectrum over the frequency range of 0–10 kHz in FSI analysis. Large Eddy Simulation (LES) model is used to capture viscous effects. The speed of the propeller is 1000 rpm and advanced velocity is varied for the systematic study carried out. The effect of advanced velocity on the maximum stress induced in the propeller, deformation of the propeller, acoustic characteristics and hydrodynamic performance of the propeller are studied using FSI method. [ABSTRACT FROM AUTHOR]

Marine propellers operate under severe service conditions and experience various corrosion forms. Electrochemical, mechanical, and biological corrosion are the three main common types of corrosion that occur on marine propellers. Electrolysis (electrolytic corrosion), being one of the electrochemical corrosion forms, has been extensively observed on marine propellers. It is the forced introduction of an external current in metals when submerged in seawater. However, it has rarely been studied for marine propellers, mostly on underground pipelines. This paper investigates the effect of electrolysis on a chromium-containing coating on copper substrate by studying the surface and cross-sectional microstructure of the substrate. It is likely that cathodic disbondment caused by high alkalinity and hydrogen evolution at the defect location were the primary reasons contributing to the failure of the coating, and the silver-colored layer deposition around the delaminated area is the corrosion product of copper–chromium oxide. The purpose of this study is to understand the electrolysis corrosion mechanism on Cu substrate and to develop a highly effective anticorrosion coating for marine propellers. [ABSTRACT FROM AUTHOR]

AbstractTribo-charging of plastic particles plays a critical role in the electrostatic separation industry, particularly for sorting millimeter-sized particles. The optimal charge/mass ratio can result in significant particle deviation in high intensity electric fields, making tribo-charging an important area of study. This work examines a modified tribo-electrostatic charging device that utilizes rotating propellers and an added air blower to increase particle charging. Through experimental analysis, the impact of air blower speed, rotating propeller speed, and sample mass was investigated using five different types of millimeter-sized particles. The results of the optimization study indicate a significant improvement in the charge/mass ratio, with the introduction of the air blower increasing the ratio by over 2.5 times. [ABSTRACT FROM AUTHOR]

In this study, a novel multirotor configuration has been developed, which utilizes a coaxial counter-rotating propeller with a large diameter at the center and four propellers with smaller diameters on four arms in an X configuration. The research pursues two main objectives. The first objective is to establish a development method for multirotors based on the well-known V-method approach in system development. The proposed method enables the design team to analyse and evaluate the multirotor at each stage of the design process, from the system to the component level, and improve the design with greater speed and accuracy. Additionally, the proposed approach can be integrated with various optimization methods, if necessary, to achieve an optimal design. The second objective is to provide the proof-of-concept of the novel multirotor configuration. This objective is pursued across different evaluation sections, from evaluating individual components to fully evaluating the multirotor, to assess the performance of this novel configuration and identify its advantages and disadvantages. The results of various evaluations demonstrate the proposed development process's practicality and proves that the novel configuration is operational and competitive with conventional multirotors in various applications. [ABSTRACT FROM AUTHOR]

This study demonstrates that the magnetic quadrupole (MQ) can make an indispensable contribution to helical dichroism (HD), which is distinct from HD caused by electric quadrupole (EQ). Specifically, the established multipole expansion theory of the light–matter interaction reveals that EQ‐induced HD belongs to the pure electric dipole–quadrupole (E1‐E2) excitation, while newly discovered MQ‐induced HD belongs to the pure magnetic dipole‐quadrupole (M1‐M2) excitation. Metallic propeller meta‐molecules are used to elaborate on this novel physical mechanism and demonstrate that HD can be significantly enhanced and flexibly tuned by increasing stereo twist of propeller meta‐molecules or slightly focusing the linearly polarized vortex beam to improve the orbital angular momentum number. Importantly, the aforementioned intriguing phenomena are validated by fabricating stereo twisted propeller meta‐molecules via nano‐kirigami method. The findings reveal a paradigm‐shift approach to manipulate the chiroptical response of a single metallic nanostructure via photonic orbital angular moment, opening prospects for optical encryption, communication, next‐generation chiroptical spectroscopy, and chiral vortex optical devices. [ABSTRACT FROM AUTHOR]

Underwater long-endurance platforms are crucial for continuous oceanic observation, allowing for sustained data collection from a multitude of sensors deployed across diverse underwater environments. They extend mission durations, reduce maintenance needs, and significantly improve the efficiency and cost-effectiveness of oceanographic research endeavors. This paper investigates the closed-loop depth control of actuation systems employed in underwater vehicles, focusing on the energy consumption of two different mechanisms: variable buoyancy and propeller actuated devices. Using a prototype previously developed by the authors, this paper presents a detailed model of the vehicle using both actuation solutions. The proposed model, although being a linear-based one, accounts for several nonlinearities that are present such as saturations, sensor quantization, and the actuator brake model. Also, it allows a simple estimation of the energy consumption of both actuation solutions. Based on the developed models, this study then explores the intricate interplay between energy consumption and control accuracy. To this end, several PID-based controllers are developed and tested in simulation. These controllers are used to evaluate the dynamic response and power requirements of variable buoyancy systems and propeller actuated devices under various operational conditions. Our findings contribute to the optimization of closed-loop depth control strategies, offering insights into the trade-offs between energy efficiency and system effectiveness in diverse underwater applications. [ABSTRACT FROM AUTHOR]

The powertrain efficiency of most small unmanned air vehicles (SUAVs) depend on the aerodynamic performance of multiple propellers, which must be modelled before its optimisation. To predict propeller performance while capturing interaction effects not accountable for by momentum theories, the Virtual Blade Model (VBM) can be used at much lower costs than conventional Computational Fluid Dynamics (CFD). However, the accuracy of VBM depends on aerofoil polar data that often misrepresent rotational and three-dimensional effects that influence small propellers. In an attempt to expand the capabilities of VBM, it is a common practice to introduce correction models for aerofoil coefficients in its formulation, but the actual effectiveness of such approach for small propeller analysis remains unassessed. In this paper, VBM in OpenFOAM was extended with stall delay and tip loss models, while aerodynamic databases at low Reynolds numbers were built with XFOIL and extrapolated to the full angle of attack range. The accuracy of three VBM versions was validated against wind tunnel measurements of two off-the-shelf small propellers. For the lower-pitch propeller, thrust and power at low advance ratios and efficiency at high advance ratios were significantly improved by the stall delay model. But for the higher-pitch propeller, thrust and power were overpredicted with extended versions of VBM under most operating conditions, which is attributable to an excessive shift of effective angles of attack to the post-stall region by the stall delay model and to uncertainties in extrapolated polar data. The results suggest that without reliable procedures for obtaining polar data, correction models should be implemented in VBM only for the simulation of low-pitch propellers operating at low advance ratios, given their avoidance of the effective angle of attack range where XFOIL and extrapolation methods are mainly expected to fail in predicting lift behaviour. • Stall delay and tip loss models are implemented into VBM, a coupled BET-CFD model. • Small propeller performance is more sensitive to stall delay than it is to tip losses. • At lower advance ratios, thrust and power results are improved by the enhanced VBM. • Unreliable post-stall data inputs into the enhanced VBM cause power overprediction. [ABSTRACT FROM AUTHOR]

The operation of marine vessels with high efficiency provides a great contribution within the scope of the International Maritime Organization and the sustainable development goals. In terms of the propulsion system, selecting the appropriate propeller is critical to effectively use the engine power installed in marine vessels because the biggest energy losses during transmission occur on the propeller and ship hull. Increasing propeller efficiencies above a certain level is quite a challenge by simply changing the number of blades, pitch, or propeller type. Therefore, various energy-saving device applications, such as propeller boss cap fins (PBCFs), are performed on the ship propeller. The effects of National Advisory Committee for Aeronautics 4415 profile PBCFs which have a different position and pitch angle integrated into the E698 model propeller have been investigated to describe efficiency, vortex, and pressure distributions based on the KRISO very large crude carrier 2 designed hull in this study. The E698 model propeller has been created by the 3D software and the validation has been performed by the computational fluid dynamic solver software based on the reference values of the propeller. The effect of four PBCF applications which have different pitches and positions on the model propeller has been revealed in terms of the efficiency, pressure distributions, and vortexes. Although P45-R45 and P45-R90 PBCF applications are quite close to the E698 propeller in terms of efficiency, no significant efficiency increase has been observed. In addition, the efficiency has decreased considerably in P90-R45 and P90-R90 applications. PBCFs application with P45-R90 has provided superiority to the base model in terms of pressure distributions and vortex formation. However, any improvement has not been achieved in the remaining three designs. Therefore, PBCF applications should be applied quite elaborately based on propeller types. [ABSTRACT FROM AUTHOR]

Large eddy simulation is adopted to analyze the interaction between the tip vortices shed by two contra-rotating propellers, by using a computational grid consisting of 4.6 × 109 points. Despite the complexity of the wake topology, the results of the computations show an excellent agreement with the measurements from an earlier experimental study on the same system. The interaction between the tip vortices shed by the two propellers produces vortex rings. Each of them consists of six helical sides, which are connected by U-shaped vortex lobes. The three upstream lobes of each vortex ring move to outer radial coordinates, as a result of their shear with the downstream lobes of the upstream vortex ring. In contrast, the downstream U-shaped lobes move to inner radial coordinates, as a result of their shear with the upstream lobes of the downstream vortex ring. This interaction results in an overall expansion of the wake of the contra-rotating propellers. The regions of shear between the U-shaped lobes of consecutive vortex rings are the areas of the largest turbulent stresses, which achieve higher levels than those produced in the wake of the two front and rear propellers working alone. This complex flow physics also triggers a faster instability of the wake system, breaking its coherence at more upstream coordinates, in comparison with the isolated propellers. [ABSTRACT FROM AUTHOR]

Traditional trim methods for isolated rotor helicopters are not suitable for intermeshing rotor compound propeller helicopters (IRcPHs) due to inherent structural differences. This study aims to establish a novel trim method for an intermeshing rotor with an auxiliary propeller. First, the relationship between the rotor cyclic pitch and the flapping response in the fully articulated rotor system with hinged extension is derived. The study then formulates the equilibrium state equations and the corresponding flight conditions for trimming the IRcPH in level forward flight. In addition, the unsteady vortex lattice method is employed to calculate the periodic averaging states on the rotor disk and correct for induced losses in flight dynamics. Finally, the paper focuses on the aerodynamic interference, blade–vortex interaction, and harmonic load patterns of the IRcPH, serving as a guide for rotor active control systems. Results show that the positions of the mutual aerodynamic interference occur constantly at 160 ° and 340 ° azimuths on the intermeshing rotor disk, serving as the phase basis for suppressing vibration. Moreover, the propeller enters the comfort zone as the forward flight speed increases, and the loads only have frequency orders of (2 / n w ) / rev with respect to the main frequency of the intermeshing rotor. [ABSTRACT FROM AUTHOR]

This experimental study investigates the effect of blade phase angle on noise attenuation in two adjacent, electronically synchronized propellers. Acoustic measurements were performed in an aeroacoustic wind tunnel with a distributed electric propulsion system that involved the adjustment of relative phase angles of 2-bladed propellers between Δψ = 0° and 90°. Ranges of advance ratios (J = 0–0.73) were investigated at a fixed propeller rotation speed of 5000 rpm. The investigation explored the impact on noise directivity and frequency characteristics. The findings reveal significant reductions in noise directivity and tonal noise at the blade pass frequency (BPF). A relative phase angle of Δψ = 90° demonstrated the maximum noise reduction, with an 8 dB decrease at the first BPF and a 2 dB reduction in overall sound pressure level at J = 0. For in-flow conditions (J > 0), a relative phase angle of Δψ = 90° resulted in significant noise reductions of about 24 dB in the first BPF and 6 dB in overall sound pressure level, compared to Δψ = 0°. These observations offer critical insights into the use of the propeller's relative phase angle as an effective noise control method in the distributed electric propulsion system. [ABSTRACT FROM AUTHOR]

At the moment, there are two neutron star X-ray binaries with massive red supergiants as donors. Recently, De et al. (2023) proposed that the system SWIFT J0850.8-4219 contains a neutron star at the propeller stage. We study this possibility by applying various models of propeller spin-down. We demonstrate that the duration of the propeller stage is very sensitive to the regime of rotational losses. Only in the case of a relatively slow propeller model proposed by Davies and Pringle in 1981, the duration of the propeller is long enough to provide a significant probability to observe the system at this stage. Future determination of the system parameters (orbital and spin periods, magnetic field of the compact object, etc.) will allow putting strong constraints on the propeller behavior. [ABSTRACT FROM AUTHOR]

Adrienne Harris´ "You Must Remember This" is a propeller to re-encounter the notion of "aprés coup," a concept that continues to defy analysand's and analyst's archetypical constructions. Taking Harris' invitation to stroll between Tangiers and Casablanca, this piece offers a voyage from the landscape of personal stories to the possibilities within relational clinic, using the savvy of music, film, literature, and philosophy, coalesced in a couple of psychic polaroids. The first polaroid frames the enigmatic presence and movement of memory, the issue of what is it that insists in session. The second, snapshots the bending movements of time and space in liminal experiences at inter-subjective spaces (session-treatment), which demands the analyst to go beyond its own "I" to maintain liminal spaces open for radical alterity to manifest. Finally, the author focuses on the notion of emptiness to create new paths, which may demand the analyst to disown its omnipotence. [ABSTRACT FROM AUTHOR]

In PROPELLER MRI, obtaining sufficient high-quality blade data remains a challenge, so the efficiency and generalization of deep learning-based reconstruction models are deteriorated. Due to narrow rotated and translated blades acquired in PROPELLER, the technique of data augmentation that is used for deep learning-based Cartesian MRI reconstruction cannot be directly applied. To address the issue, this paper introduces a novel approach for the generation of synthetic PROPELLER blades, and it is subsequently employed in data augmentation for undersampled blades reconstruction. The principal aim of this study is to address the challenges of reconstructing undersampled blades to enhance both image quality and computational efficiency. Evaluation metrics including PSNR, NMSE, and SSIM indicate superior performance of the model trained with augmented data compared to non-augmented counterparts. The synthetic blade augmentation significantly enhances the model's generalization capability and enables robust performance across varying imaging conditions. Furthermore, the study demonstrates the feasibility of utilizing synthetic blades exclusively in the training phase, suggesting a reduced dependency on real PROPELLER blades. This innovation in synthetic blade generation and data augmentation technique contributes to enhanced image quality and improved generalization capability of the associated deep learning model for PROPELLER MRI reconstruction. [ABSTRACT FROM AUTHOR]

In efforts to achieve the goal of reducing ship emissions in the fight against climate change, reducing fuel consumption by making ships lighter is stated as one of the solutions. In this study, the possibilities of making composite equivalents of propellers, which are the most complex ship elements and traditionally produced from metal materials, are investigated with the advantages of additive manufacturing, which offers a rapid production opportunity for such forms. In this way, a lighter composite propeller and, therefore, a lighter ship will be achieved, and negative environmental impacts, especially harmful emissions, will be reduced. In the study, a 1/14-scale ship propeller was produced through the material extrusion method of additive manufacturing using an HDPE composite containing long carbon fiber with a 15% weight fraction. An attempt to reduce flexibility with an epoxy-carbon fabric prepreg coating was made, as the flexibility has negative effects on the performance of the produced propeller. The propeller tunnel test showed that the applied carbon fabric epoxy prepreg helped to improve the propeller's performance by decreasing the flexibility of the propeller and reducing the deformation at the tips. At the same time, the propeller weight was decreased by 60% compared to its metal counterparts. [ABSTRACT FROM AUTHOR]

Background: The efficacy and safety of perforator-based propeller flaps (PPF) versus free flaps (FF) in traumatic lower leg and foot reconstructions are debated. PPFs are perceived as simpler due to advantages like avoiding microsurgery, but concerns about complications, such as flap congestion and necrosis, persist. This study aimed to compare outcomes of PPF and FF in trauma-related distal lower extremity soft tissue reconstruction. Methods: We retrospectively studied 38 flaps in 33 patients who underwent lower leg and foot soft tissue reconstruction due to trauma at our hospital from 2015 until 2022. Flap-related outcomes and complications were compared between the PPF group (18 flaps in 15 patients) and the FF group (20 flaps in 18 patients). These included complete and partial flap necrosis, venous congestion, delayed osteomyelitis, and the coverage failure rate, defined as the need for secondary flaps due to flap necrosis. Results: The coverage failure rate was 22% in the PPF group and 5% in the FF group, with complete necrosis observed in 11% of the PPF group and 5% of the FF group, and partial necrosis in 39% of the PPF group and 10% of the FF group, indicating no significant difference between the two groups. However, venous congestion was significantly higher in 72% of the PPF group compared to 10% of the FF group. Four PPFs and one FF required FF reconstruction due to implant/fracture exposure from necrosis. Additionally, four PPFs developed delayed osteomyelitis post-healing, requiring reconstruction using free vascularized bone graft in three out of four cases. Conclusions: Flap necrosis in traumatic lower-leg defects can lead to reconstructive failure, exposing implants or fractures and potentially causing catastrophic outcomes like osteomyelitis, jeopardizing limb salvage. Surgeons should be cautious about deeming PPFs as straightforward and microsurgery-free procedures, given the increased complication rates compared to FFs in traumatic reconstruction. Data access statement: The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request. [ABSTRACT FROM AUTHOR]

Utilization of chiral frustrated Lewis pairs as catalysts in enantioselective hydrogenation of unsaturated molecules represents a promising approach in asymmetric synthesis. In our effort to improve our current understanding of the factors governing the stereoselectivity in these catalytic processes, herein we examined the mechanism of direct hydrogenation of aromatic enamines catalyzed by a binaphthyl–based chiral amino–borane. Our computational analysis reveals that only one particular conformer of the key borohydride reaction intermediate can be regarded as a reactive form of this species. This borohydride conformer has a well–defined chiral propeller shape, which induces facial selectivity in the hydride transfer to pro–chiral iminium intermediates. The propeller chirality of the reactive borohydride conformer is generated by the axially chiral binaphthyl scaffold of the amino–borane catalyst through stabilizing π‐π stacking interactions. This new computational insight can be readily used to interpret the high degree of stereoinduction observed for these reactions. We expect that the concept of chirality relay could be further exploited in catalyst design endeavors. [ABSTRACT FROM AUTHOR]

Purpose: Water jet propulsion is widely used in various military and civilian fields due to its advantages of simple structure and high propulsion efficiency. The process of mooring involves utilizing specially designed equipment to secure a ship at a designated berth. During the process of water jet propulsion, the single propeller operates within a complex and turbulent three-dimensional flow. Hence, studying the coupling between the water jet propeller and the hull is critical to comprehending the characteristics of the device and the distribution of the flow field in detail. Design/methodology/approach: Firstly, we conducted computational fluid dynamics (CFD)-based self-propulsion calculations to evaluate the interaction between the hull and the propeller. We subsequently analyzed the propeller's performance and the forces acting on the hull to understand how the presence or absence of the hull influenced the water jet propeller. Finally, we performed calculations and analysis of the cavitation characteristics of the coupling between the hull and the water jet propeller, considering different rotational speeds and water depths at the bottom of the pool. Findings: The study demonstrated that the presence of the hull boundary layer under the hull-propeller coupling condition led to reduced uniformity of propeller inlet flow and lower efficiency of the propulsion pump. However, it also increased the bias toward low-flow conditions. Additionally, increasing the impeller speed led to a gradual increase in the cavitation volume within the water jet propeller, resulting in a gradual decrease in the propeller's performance. Originality/value: This research provides the technical support required for effective design and operation of water jet propulsion systems. This paper involves studying and analyzing the performance and flow field of the coupling between the hull and propeller under mooring conditions with a specified hull model. [ABSTRACT FROM AUTHOR]

Electric vertical takeoff and landing (eVTOL) vehicles possess high payload transportation capabilities and compact design features. The traditional method of increasing propeller size to cope with high payload is no longer applicable. Therefore, this study proposes the use of coaxial counter-rotating propellers as the lift system for eVTOL vehicles, consisting of two coaxially mounted, counter-rotating bi-blade propellers. However, if the lift of a single rotating propeller is linearly increased without considering the lift loss caused by the downwash airflow generated by the upper propeller and the torque effect of the lift system, it will significantly impact performance optimization and safety in the eVTOL vehicles design process. To address this issue, this study employed the Moving Reference Frame (MRF) method within Computational Fluid Dynamics (CFD) technology to simulate the lift system, conducting a detailed analysis of the impact of the upper propeller's downwash flow on the aerodynamic performance of the lower propeller. In addition, the aerodynamic performance indicators of coaxial counter-rotating propellers were quantitatively analyzed under different speed conditions. The results indicated significant lift losses within the coaxial contra-rotating propeller system, which were particularly notable in the lift loss of the lower propeller. Moreover, the total torque decreased by more than 93.8%, and the torque was not completely offset; there was still a small torsional effect in the coaxial counter-rotating propellers. The virtual testing method of this study not only saves a significant amount of time and money but also serves as a vital reference in the design process of eVTOL vehicles. [ABSTRACT FROM AUTHOR]

Compact multi-rotor unmanned aerial vehicles (UAVs) can be operated in many challenging environmental conditions. In case the UAV requires certain considerations in designing like lightweight, efficient propulsion system and others depending upon the application, the hybrid UAV comes into play when the usual UAV types cannot be sufficient to meet the requirements. The propulsion system for the UAV was selected to be coaxial rotors because it has a high thrust-to-weight ratio and to increase the efficiency of the propulsion system, a unique propeller was proposed to achieve higher thrust. The proposed propeller was uniquely designed by analyzing various airfoil sections under different Reynolds's number using X-Foil tool to obtain the optimum airfoil section for the propellers. Since the design with duct increases efficiency, the Hybrid UAV presented in this paper has the modified novel convergent–divergent (C–D)-based duct which is a simplified model of a conventional C–D duct. The yawing and rolling maneuverings of the UAV could be achieved by the thrust vectoring method so that the design is simpler from a structural and mechanical perspective. The use of UAVs has risen in recent years, especially compact UAVs, which can be applied for applications like surveillance, detection and inspection, and monitoring in a narrow region of space. The design of the UAV is modeled in CATIA, and its further performance enactment factors are picked from advanced computational simulations relayed bottom-up approach. The predominant computational fluid dynamics (CFD) and fluid structure interaction (FSI) investigations are imposed and optimized through Computational Analyses using Ansys Workbench 17.2, which includes analysis of structural behaviour of various alloys, CFRP and GFRP based composite materials. From the structural analysis Titanium alloy came out to be the best performing materials among the others by having lower total deformation and other parameters such as normal and equivalent stress. The dynamics control response is obtained using MATLAB Simulink. The validations are carried out on the propeller using a thrust stand for CFD and on the duct through a high-jet facility for structural outcomes to meet the expected outcome. [ABSTRACT FROM AUTHOR]

In the field of electric aircraft, the axial force of the conical motor is used to offset propeller thrust and reduce bearing wear. For the problem of accurate calculation of the no‐load axial force of the conical motor, combined with the characteristics that the rotor magnetic bridge of the hybrid conical inner‐mounted permanent magnet synchronous motor (HC‐IPMSM) is easy to be saturated and difficult to be calculated analytically, an equivalent analytical calculation method is proposed. According to the principle of constant air‐gap magnetic flux, the HC‐IPMSM is equivalent to many cylindrical surface‐mounted permanent magnet synchronous motors (CY‐SPMSM), and an analytical model is gained. Combining with the scalar magnetic potential Laplace equation and Poisson equation, the air‐gap flux density distribution on the rotor surface is calculated. And finally, the no‐load axial force of the motor is obtained by using the cone angle and the Maxwell stress method. Simulation and experiments verify the correctness and validity of the analytical model. [ABSTRACT FROM AUTHOR]

Ducted propellers present broad applicability in urban air mobility vehicles due to their enhanced operational safety, improved aerodynamic performance, and potential to mitigate noise emissions. This study proposes a numerical approach for designing adequate duct geometries, focusing on the duct's lip profile, expansion ratio, and tip clearance, aiming to provide valuable design guidance for ducted propellers. The simulations are validated through experimental data, showing reasonable agreement in terms of thrust generation and far-field noise. The mean flow and generated thrust are characterized with a parametric study using steady simulations, while delayed detached eddy simulations are employed to capture transient flow characteristics and investigate noise generation. The noise levels were computed using the integral solution of the Ffowcs-Williams and Hawkings equation. The lip geometry impacts the flow distribution and generated thrust, modifying the tonal noise. Furthermore, slightly divergent ducts can increase the total thrust by minimizing flow separation on the duct wall while increasing the suction on the duct lip. The primary noise sources are identified at the propeller's leading edge and tip. The results reveal that divergent ducts effectively reduce tonal noise at all observer angles but increase broadband noise, attributed to the noise sources at the leading edge of the propeller and the interaction with the duct lip. Additionally, reducing the tip clearance from 2 to 1 mm enhances the total thrust by more than 20% without causing extra noise generation. [ABSTRACT FROM AUTHOR]

With the development of the large and high-speed ships, the cavitation and radiated noise of marine propellers have been more and more concerned. This paper presents a numerical simulation of marine propellers with the ridge structures, inspired by the airfoils with the bionic ridge surfaces. The bionic method is applied to redesign the blade sections of a marine propeller, and the ridge structures are arranged between the leading edge and the thickest point. Four bionic propellers are established by changing the style and distribution area of the ridge structures on the blade surface. The cavitation morphology, pressure distribution and open water characteristics are analyzed with the software STAR CCM +. The numerical model is validated with the test data and the results show that the ridged structures can make the low-pressure area on the blade surface more dispersed and suppress cavitation. Compared with the prototype propeller, the four bionic propellers with the ridge structures can reduce the cavitation area by 26% (with an advance speed coefficient of 0.5) to 30% (with an advance speed coefficient of 0.3) at medium and low advance speeds. Besides, one of the bionic propellers can improve the thrust and efficiency by 14.93% and 1.61% respectively at high advance speeds. [ABSTRACT FROM AUTHOR]

Wind propulsion systems (WPS) for commercial ships can be a key ingredient to achieving the IMO green targets. Most WPS installations will operate in conjunction with propellers and marine engines in a hybrid mode, which will affect their performance. The present paper presents the development of a generic, fast, and easy tool to predict the propeller and engine performance variation, along with the cost, as a function of the wind power installed in two operation conditions: fixed ship speed and constant shaft speed. Specific focus is directed toward showing generic trends and trade-offs that inform economic decision-making. To this end, a key feature of the presented work is the ability to assess the cost–benefit of both controllable pitch propellers and fixed pitch propellers (CPPs and FPPs). This provides advice on when, in terms of WPS installation size, it is worthwhile to install which kind of propeller. CPPs are found to be more suitable for newly built wind-powered ships (>70% wind power), while a conventional FPP is satisfactory for wind-assisted ships (<70% wind power) and retrofitted installations. The results for a 91,373 GT bulk carrier showed that a WPS unloads the propeller and the engine, which leads to an increase in the propulsive efficiency and a detrimental rise of the engine specific fuel oil consumption. However, propeller gains are found to be greater than engine losses, which result in extra savings. Thus, not only does a WPS save fuel and corresponding pollutant emissions, but it also increases the entire propulsive efficiency. [ABSTRACT FROM AUTHOR]

This study presents a predominantly numerical and theoretical investigation into the balance of tonal and broadband noise due to an isolated propeller in uniform motion. The predicted trends in the balance between tonal and broadband noise radiation with varying blade number and speed of rotation is supported by preliminary experimental measurements. Here, we assume that the dominant noise generation mechanisms are the tones due to steady loading and blade thickness, while the broadband noise is due to boundary layer scattering at the trailing edge. The study also provides a detailed comparison between the tonal and broadband formulations to highlight their similarities and differences. In this paper, we show that the main differences in the behaviour and character of the tonal and broadband spectra and directivities are due to the number of acoustic modes that can be excited. This paper presents a parametric study in which the variation in tonal and broadband noise is investigated as a function of blade tip Mach number (M t ) and blade number (B) whilst maintaining constant solidity and thrust. This study is repeated for three NACA airfoil profiles. It is found that tonal noise dominates at low blade number and low frequency and/or higher tip speeds, while broadband noise is the major contributor at high-frequencies and at high blade number and low tip speeds. The results show a clear distinction between the combinations of M t and B that are dominated by tonal and by broadband noise. These results are interpreted from fundamental principles relating to modal radiation efficiencies. We confirm this trend of balance between tonal and broadband noise with measured noise at different B and M t . The results of this paper will serve as useful guidelines for preliminary propeller design. [ABSTRACT FROM AUTHOR]

A propeller blade has a significant effect on the performance of a propulsion system. It is of great significance to develop an efficient and accurate optimization strategy for propeller design in the preliminary stage. A key concept of the design is to establish a fast hybrid aerodynamic optimization framework employing the reformulated Blade Element Momentum (rBEM) model to optimize the propeller blade shape under cruising conditions. First, the rBEM numerical model is established and validated with the experimental data in both hover and forward-flight cases. Second, a fast hybrid design optimization strategy based on the rBEM model is developed, which divides the propeller design process into gradient-free planform optimization and gradient-based airfoil optimization. The planform and sectional designs are coupled with each other in an iterative manner until convergence criteria is reached. Based on the proposed optimization strategy, the hybrid design process shows gradual convergence. The efficiency of the optimized propeller has been increased by 29.84% when compared with the baseline propeller. The solidity ratio of the optimal propeller is smaller than that of the baseline propeller, which has a smaller chord length distribution, a larger twist angle distribution, and lesser camber and thickness of the cross-sectional airfoil. [ABSTRACT FROM AUTHOR]

Is it possible to remotely operate a tiny piece of matter or a less-than-one-centimeter machine to perform a medical task in life? Especially given that in the present technology, neither the mechanism nor battery is small enough to be set up inside the structure of such a tiny machine. Yet, if the powered matter is magnetically responsive, then a magnetic field, as one of the potential power sources, can be applied to power it promisingly. Herein, the concept of electromechanical energy conversion is utilized through a specific configuration consisting of eight solenoids arranged together as a nest. The device converts electrical energy into an electromagnetic field, and finally, into mechanical energy, respectively, resulting in magnetic manipulation. Since electric energy is supplied to the configuration, eight solenoids generate the controllable magnetic field in both direction and magnitude by means of the superposition technique. The device can magnetically navigate tiny motorless matter to release mechanical energy through the 3D-controllable motion to arbitrary positions effectively and physical interactions with the surrounding environment as if operating a tiny machine. The experimental results report the feasibility of the device to control the 6-DOF locomotion of small matter precisely. The contribution of the concept based on this work leads to a promising protocol to remotely power small machines, micro-engines, micro-propellers, micro-turbines, etc. [ABSTRACT FROM AUTHOR]

On Distributed Electric Propulsion (DEP) aircraft, the deployment of numerous high-lift propellers with small diameters on the wing's leading edge significantly enhances lift during low-speed flight. The increase in the number of propellers leads to a decrease in diameter, which increases the disc loading. In this paper, a rapid design method applicable to heavy-loaded propellers is developed and does not require iterative calculations compared to traditional heavy-loaded propeller design methods, enabling rapid completion of the propeller design. The results of CFD computation show that the relative thrust error of the method proposed in this paper is within 5% for disc loading ranging from 600 Pa to 1400 Pa, features a high-accuracy design of propellers with required thrust, and high thrust coefficients are achieved within large advance ratio range. [ABSTRACT FROM AUTHOR]

The ball and beam experimental platform is an unstable nonlinear system widely used as a benchmark control setup for testing different controller approaches, especially for beginners on automatic control to improve their control knowledge skills. In this paper, we innovate it by governing the angular position of the beam with a twin-rotor system. Our experiment consists of a beam that rotates through a pivot, in which two propellers are attached to the ends of this beam. Hence, we have a recent one-degree aerial device, and instead of using a ball, we employ a mass moving on the beam, presenting friction on position to its movements on the beam. Then, the control objective is to regulate the mass position at some predefined zone on the beam, ensuring stability and robustness in front of external perturbations and unmodeled uncertainties. To do so, we define a classical PI controller. To assess closed-loop robustness, a mass was introduced to one propeller to induce perturbation, thereby simulating modeling variations or disturbances. The experimental results prove the goodness of our experimental platform for drone applications. [ABSTRACT FROM AUTHOR]

This paper presents numerical simulations of propeller–hull interaction of a ship model for the dynamic condition, demonstrating the ability of the developed self-propulsion module in OpenFOAM. A dynamic motion class has been developed based on the sliding mesh method to simulate a rotating propeller with ship motions. A body-force method is also implemented to simulate propeller–hull interaction to reduce the computational cost of propeller modeling. Validation studies were carried out for the Japan Bulk Carrier (JBC) ship model. The bare-hull resistance, sinkage, and trim are verified against the experimental data. The propeller open-water hydrodynamic characteristics are then computed and validated using sliding mesh and body-force methods. Finally, the self-propulsion simulations are carried out for the JBC model in calm water with sinkage and trim at the design speed. Numerical predictions of the self-propulsion parameters and axial flow velocity distributions at different transverse locations are presented. [ABSTRACT FROM AUTHOR]

The current project uses computational studies to design and improve a new type of small propeller used in unmanned aerial vehicles. The design process started with selecting the appropriate airfoils for the new propeller and then investigating the effects of changing the airfoil, angle of attack and rotational speed on its aerodynamic performances. The numerical simulation of the turbulent flow produced by the propeller's rotation is carried out using the commercial calculation code ANSYS Fluent 14.0. Numerical results show that the newly developed propeller has a 116% improvement in thrust force compared to the commercial propellers used in today's UAVs. Furthermore, the values of the critical angles strongly depend on the propeller's rotational speed. Higher critical angles of attack could be reached (without the boundary layer getting separated) in low RPMs than in high RPMs. On the other hand, the thrust force increases when the rotation speed increases. Therefore, the selection of the angles of attack strongly depends on the rotation speed range desired. [ABSTRACT FROM AUTHOR]

Marine propellers work under severe service conditions, where they commonly suffer from mechanical, electrochemical, and biological corrosion damage. The major mechanical corrosion involves cavitation, erosion, and impingement corrosion. On the other hand, the major electrochemical corrosion involves galvanic corrosion and electrolysis. As a result, consideration of both desired mechanical and electrochemical properties is necessary when designing a marine propeller coating. In this study, a PVB (polyvinyl butyral) and an epoxy coating were formulated without corrosion inhibitors to investigate the desired coating properties for marine propeller applications. The two coatings were compared with a Cr-containing commercial marine propeller coating to investigate the advantages and disadvantages of using PVB and epoxy for marine propeller coatings. It was found that it is desirable for marine propeller coatings to be flexible to avoid cracking and flaking; to be able to withstand high pH in order to resist cathodic disbondment (electrolysis); to have adequate primer–substrate adhesion; and, ideally, to be able to self-heal when the coating is damaged (cavitation). It was found that the PVB-ZO coating has more desirable properties, and introducing self-healing properties could be one of the options for further optimization in the future. [ABSTRACT FROM AUTHOR]

Background The aim of our study was to evaluate a new propeller vascularized lymphatic tissue flap (pVLNT) combined with aligned nanofibrillar collagen scaffolds (CS) (BioBridge) in reducing lymphedema in the rat lymphedema model. Methods Unilateral left hindlimb lymphedema was created in 15 female Sprague–Dawley rats following inguinal and popliteal lymph nodes (LN) resection and radiation. An inguinal pVLNT was elevated from the contralateral groin and transferred through a skin tunnel to the affected groin. Four collagen threads were attached to the flap and inserted in the hindlimb at the subcutaneous level in a fan shape. The three study groups consisted of group A (control), group B (pVLNT), and group C (pVLNT + CS). Volumetric analysis of both hindlimbs was performed using micro-computed tomography imaging before the surgery (at initial time point) and then at 1 and 4 months, postoperatively, and the relative volume difference (excess volume) was measured for each animal. Lymphatic drainage was assessed by indocyanine green (ICG) fluoroscopy for number and morphology of new collectors and the time required for ICG to move from injection point to the midline. Results Four months after the induction of lymphedema, an increased relative volume difference remained in group A (5.32 ± 4.74%), while there was a significant relative volume reduction in group B (−13.39 ± 8.55%) and an even greater reduction in group C (−14.56 ± 5.04%). ICG fluoroscopy proved the functional restoration of lymphatic vessels and viability of pVLNT in both B and C groups. Notably, only group C demonstrated statistically significant improvements in lymphatic pattern/morphology and in the number of lymphatic collectors as compared with the control group A. Conclusion The pedicle lymphatic tissue flap combined with SC is an effective procedure for the treatment of lymphedema in rats. It can be easily translated into treatment of humans' lower and upper limb lymphedema and further clinical studies are warranted. [ABSTRACT FROM AUTHOR]

Improving the performance of surface-piercing propellers is achieved by investigating the influential factors. In this study, Artificial Neural Network is used to identify nonlinear models for estimating various phenomena. Non-Dominated Sorting Genetic Algorithm II is considered as an optimization tool. In this study, in order to optimize the position parameters, including the immersion ratio, angle of attack, and yaw angle, data from experimental tests at the HYDROTECH center of IUST were collected as the initial data field for the generation of training data by the artificial neural network, then experimental tests were implemented in the position of the Non-Dominated Sorting Genetic Algorithm II proposed as the output, and the results were compared. The Artificial Neural Network results showed that the mean error of the trained verified and test data is 7.5e−5, 1e−4, and 1e−4, respectively. Comparing the experimental and optimization results, the thrust coefficient showed a relative error of 9.7%, while the torque coefficient showed a relative error of 7.5%, this algorithm can be used as a cost-effective, time-saving method for a similar problem. [ABSTRACT FROM AUTHOR]

A G-rich core sequence G3-TCA-G3-T1,2-G3-T1,2-G3 can be designed to fold into a parallel or into two different (3+1) hybrid-type G-quadruplexes, among them an elusive topology with one lateral followed by two propeller loops. Favored folds can be rationalized based on the number of intervening thymidines and on additional complementary flanking sequences. [ABSTRACT FROM AUTHOR]

To realize a propeller-driven Mars airplane, the propeller-wing flow interaction characteristics should be clarified. Thus, we conducted numerical simulations of the propeller-wing interaction at low Reynolds number conditions (Re = 3.0 © 104) corresponding to Mars atmosphere, focusing on the propeller slipstream effects on the fixed wing. Solutions for the tractor case (propeller in front of the fixed wing) and the wing only case were compared. The results showed that in the tractor case, the lift coefficient (CL) of the fixed wing increased with the angle of attack (¡) more linearly than for the wing only case and showed delayed stall because the propeller slipstream favorably suppressed the expansion of the recirculation region over the fixed wing in the time-averaged flow fields, supporting the experimental result. The flow over the fixed wing separated from near the leading-edge in both low and high thrust conditions even at a moderate angle of attack (¡ = 5°), whereas previous studies at relatively high Reynolds numbers (Re = O(105)) showed that almost attached flow fields were formed under the propeller slipstream influence. Additionally, it was observed that the CL fluctuation of the fixed wing increased even when the time-averaged CL was lower than that of the wing only case. [ABSTRACT FROM AUTHOR]

Rowing motion with paired propellers is an essential actuation mechanism for swimming robots. Previous work in this field has typically employed flexible propellers to generate a net thrust or torque by using changes in the compliance values of flexible structures under the influence of a fluid. The low stiffness values of the flexible structures restrict the upper limit of the oscillation frequency and amplitude, resulting in slow swimming speeds. Furthermore, complex coupling between the fluid and the propeller reduce the accuracy of flexible propeller simulations. A design of a flexible passive joint paddle was proposed in this study, and a dynamics model and simulation of the paddle were experimentally verified. In order to optimize the straight swimming speed, a data-driven model was proposed to improve the simulation accuracy. The effects of the joint number and controller parameters on the robot's straight swimming speed were comprehensively investigated. The multi-joint paddle exhibited significantly improved thrust over the single-joint paddle in a symmetric driving mode. The data-driven model reduced the total error of the simulated data of the propulsive force in the range of control parameters to 0.51%. Swimming speed increased by 3.3 times compared to baseline. These findings demonstrate the utility of the proposed dynamics and data-driven models in the multi-objective design of swimming robots. [ABSTRACT FROM AUTHOR]