Conventional Propeller Research Articles

Large eddy simulation of a marine propeller with leading edge tubercles

The results of large eddy simulations on a cylindrical grid consisting of 5.8 × 109 points are reported, dealing with marine propellers with leading edge tubercles (LETs). They are compared with the performance and flow fields of the baseline geometry without tubercles. In general, the efficiency of propulsion is not improved, but a substantial effect is produced on the development of the flow across the propeller blades. The minima of pressure on the suction side of the blades are confined in the troughs of the leading edge, with the potential of reducing the overall extent of the area of cavitation (cavitation funneling effect). In addition, local maxima of turbulence are produced on the suction side of the blades by the onset of streamwise vortices at the troughs of the LETs. Although the wake development is slightly modified across blade geometries, no obvious influence of the LETs on the major wake structures is observed. Due to their early breakup, the vortices developing across the span of the propeller blades, including those originating at the LETs, are able to affect indeed a very short extent of the propeller wake. Its dynamics is still dominated by the tip and hub vortices, as for the conventional design of the propeller. Meanwhile, the intensity of the root vortices shed by the conventional propeller is substantially reduced in the wake of the tubercled propellers, thanks to the modified geometry of the blades at their root, resulting also in a slightly slower instability of the hub vortex.

Effect of Bio-Inspired Cutout Shapes at the Leading Edge of Propellers on Noise and Flight Efficiency

In recent years, the application of bio-inspired structures has garnered attention for enhancing the performance of fluid machinery. In this study, we experimentally investigated the effects of introducing a bio-inspired cutout structure to the propellers of drones, aiming to improve thrust efficiency and reduce noise levels. Our results demonstrated reductions in noise levels compared to conventional propellers. Parametric studies revealed that the roundness of the structure significantly influenced both flight efficiency and noise levels, suggesting its importance for replicating the inherent fluid characteristics found in nature. Additionally, optimal parameters for noise reduction, such as the length of the cutout, angle of incision relative to the flow direction, and the distance between the gap were identified. Although no improvements in flight efficiency were observed, most of the models investigated exhibited only around a 5% reduction in efficiency compared to the standard propellers, suggesting practical applicability for scenarios such as nighttime drone operations in urban areas. The noteworthy reduction in sound pressure levels in the mid- to high-frequency range achieved by the bio-inspired propellers in this study holds the potential to address the issue of drone noise pollution and encourage drone operations in urban areas. Moreover, the confirmed decrease in sound pressure at specific frequencies and the suggested controllability hint at the possibility of enhancing sound source localization performance using drones.

Benchmarking of Aerodynamic Models for Isolated Propellers Operating at Positive and Negative Thrust

Operating a conventional propeller at negative thrust results in the operation of positively cambered blade sections at negative angles of attack, leading to flow separation. Consequently, accurately simulating the aerodynamics of propellers operating at negative thrust poses a greater challenge than at positive thrust. This study offers a comprehensive assessment of the aerodynamic modeling capabilities of numerical methods, spanning low to high fidelity, for computing propeller performance across both positive and negative thrust regimes. Low-fidelity methods, namely, blade-element momentum and lifting line theories, effectively predict propeller performance trends at positive thrust. However, they fail to capture trends at negative thrust beyond the maximum power output point due to the neglect of three-dimensional flow effects. Both steady and unsteady Reynolds-averaged Navier–Stokes (RANS) simulations with y+<1 perform well across both positive and negative thrust conditions, with errors below 2% for both thrust and power magnitudes near the maximum power output point. Lattice-Boltzmann very-large-eddy simulations (LB-VLESs) with y+≤10 exhibit excellent agreement with experimental data with less than 1% error near the maximum power output point but with significant computational costs. Conversely, LB-VLESs with y+≥15 offer a more economical approach to capture general trends with the computational cost of the same order as unsteady RANS. However, wall models introduce errors in modeling flow separation, leading to a 16% overestimation of power magnitude near the maximum power output point. The results highlight the necessity of using tools with increased fidelity levels when considering propeller operation at negative thrust compared to the conventional positive thrust regime.

A GPU-accelerated 3dBEM supporting the optimization of actively morphing flapping-foil thrusters with application to AUV propulsion

In recent years, flapping thrusters have been getting attention as an eco-friendly alternative to conventional propellers for autonomous underwater vehicles (AUVs) mainly due to their low-frequency operation, advanced maneuverability, and high efficiency. Their operating principle mimics the thrust-producing kinematics found among efficient swimmers in the aquatic environment. The present work focuses on the analysis and optimization of flapping systems with active morphing features for increased performance. The two optimization studies refer to a realistic AUV propulsion scenario for a wing thruster with active hydrofoil-section adjustment, spanwise bend and twist morphing capabilities. A gradient descent approach based on sequential quadratic programming (SQP) is used for optimal tuning of design variables (planform shape, kinematics) targeting efficiency maximization under thrust and effective angle of attack constraints. For the evaluation of each candidate thruster the unsteady boundary element solver 3dBEM is developed and used for wing performance prediction. The solver exploits GPU parallel computation techniques to reduce computational time and enable fast optimization. Results indicate that the optimal thruster with chordline/spanwise bending is 25% more efficient, whereas the same result for the wing with spanwise bending and twist profiles is up to 8.8%. The 3dBEM solver can support the preliminary design process of morphing flapping-foil thrusters.

Experimental Propeller Performance Analysis of Distributed, Single and Isolated configurations

Distributed propulsion (DP) configurations are a promising concept for future aircraft systems. The main objective of the presented experiment is to investigate aerodynamic interactions of such configurations in detail and compare DP results to a single propeller configuration. The experimental setup at the Propulsion Test Facility, TU Braunschweig, features three co-rotating propellers. These are not attached directly to the wing, but are mounted on a separate carrier. This decoupling allows the forces and moments acting on wing and propeller to be considered separately. Additionally, different relative propeller positions are set up easily. In order to eliminate side wall effects, only the centre propeller and the centre wing element are subject of investigation for the distributed configuration. The periodically repeating outboard propellers reduce the wind tunnel interference while providing a true DP setup for the instrumented centre. Additionally to the DP setup, tests for conventional propeller wing configurations (only centre propeller installed) as well as isolated propeller and clean wing tests were performed. Thus, the DP effects on wing and propeller and the effect of the downstream wing on the propeller are clearly identified. The comparison between single propeller and distributed propulsion configurations shows that with distributed propulsion the drag increase is reduced from 326% to 216% compared to a clean wing. This effect is intensified by a greater thrust level and higher angles of attack. In order to identify the distributed propulsion effects, the forces acting on the propeller as well as the resulting efficiency of the propeller are compared between the distributed and single propeller configuration for two different relative propeller positions. The efficiency of the centre propeller is increased due to the outer propellers by approx. 2% to 3%.

Experimental investigations on aerodynamic and psychoacoustic characteristics of three-blade looprop propeller

Aeroacoustic noise in multiple rotor drones has been increasingly recognized as a crucial issue. This study focuses on addressing this challenge by introducing a novel low-noise looprop propeller design with three blades. Unlike traditional propellers, the looprop propeller utilizes three closed-loops to generate thrust. Through comprehensive experimental investigations conducted in an anechoic chamber using a hover stand test, we conducted an integrated study of the propeller's aerodynamic, aeroacoustic, and psychoacoustic characteristics. The results demonstrate that the three-blade looprop propeller achieves a notable reduction in the overall sound pressure level (OASPL), particularly in tonal noise at the blade passing frequency where the tone reduction amounts to approximately 15 dB. Additionally, we employed Zwicker psychoacoustic annoyance models to evaluate the propellers' psychoacoustic performance and discussed the environmental noise mask effect. The findings indicate that the three-blade looprop propeller exhibits an improved sound quality while maintaining aerodynamic performance comparable to that of conventional propellers. Overall, our study suggests that the looprop propeller design offers significant advancements in acoustic performance, particularly in terms of psychoacoustic characteristics. These findings hold promising implications for the field of drone technology and the potential for notable improvements in noise reduction.

Scale Effect of a Kappel Tip-Rake Propeller

In this paper, the scale effect of Kappel tip-rake propellers with different end plate designs was studied using computational fluid dynamics. Given the base size of the mesh and the appropriate numerical model for the determined simulation, the open-water performance of three Kappel propellers with different bending degrees of the end plate at different scales was calculated. Comparing the scale effect of these propellers, the scale effect of the torque coefficient of a Kappel propeller is more intense than that of the conventional propeller. In addition, the scale effect of the torque coefficient is strong when the bending degree of the end plate increases, dwarfing the scale effect on the thrust coefficient. Following the research on the scale effect of the wake field for the Kappel propeller, the laws that reveal the influence of the scale on the wake field were summarized; that is, the high-speed zone in the wake relatively expands with the increase of the scale in company with a trend of tip cross flow. The research reveals the basic variation trend and rule of the open-water performance and wake distribution for the Kappel propeller under different scales within the Reynolds number range of 4.665×105−8.666×107 considering γ transition, as well as the characteristic differences between the Kappel propellers with different end plate designs, which will be of great significance to its optimization design and application to marine vehicles of different scales.

Design, analysis and test of conventional and winglet propellers under highly loaded conditions

In this paper, some conventional and winglet inboard propellers are designed, analyzed and tested under highly loaded conditions. The design objective is to achieve the highest efficiency at a given propeller RPM and target power. A non-linear optimization solver is coupled with the panel method to design the conventional propellers. A robust parameterized geometry definition is given for the winglet propellers, with the flexibility to change the shapes of the winglet, including its location and direction, and its sections’ pitch and camber. The winglet propellers are designed using the SHERPA (Simultaneous Hybrid Exploration that is Robust, Progressive, and Adaptive) algorithm and the performance of each geometry in the optimization process is predicted by the steady RANS (Reynolds-Averaged Navier–Stokes) method with periodic boundary conditions. Both the conventional propellers and winglet propellers are designed under the open water condition and multiple designs are further analyzed by the unsteady RANS method, together with the hull, the rudder, the free surface and an inclined shaft angle. It is found that (i) in the conventional propeller designs, the unsteadiness in propeller-induced forces on the hull reduces with increased distance from the propeller blade tip to the bottom of the hull; (ii) the efficiency of optimized conventional propellers generally decreases with the decrease of propeller diameter; (iii) under the specified design conditions, the blade tips of the optimized winglet propellers exhibit a tendency to bend towards the pressure side of the blade; (iv) when appropriately designed, winglet propellers can attain enhanced efficiency and reduced unsteadiness in propeller-induced forces acting on the hull’s underside, in comparison to conventional propellers of the same overall diameter. Consequently, winglet propellers are good design choices for highly loaded conditions with strict constraints on diameter. Finally, one conventional propeller design and one winglet propeller design are selected to make full-scale prototypes and tested on the water, where the fuel economy of these prototypes is measured and compared with the numerical predictions. The results demonstrate that the winglet design surpasses the optimal conventional propeller design, yielding a 13.2% improvement in fuel economy under light conditions and a 9.3% improvement under heavy conditions. These findings substantiate the advantages of utilizing winglet designs for propellers operating under highly loaded conditions.

Влияние неравномерности потока за корпусом модели одновального судна на гидродинамические и кавитационные характеристики отдельной лопасти в составе гребного винта

Object and purpose of research. This paper investigates wake non-uniformity effect of single-shafter model upon local and integral hydrodynamic and cavitation parameters of separate blade of its propeller. The study was performed on propeller models KP505 and containership models KCS. Materials and methods. Local and integral hydrodynamic parameters of propeller and container ship were obtained as per CFD methods. Viscous flow parameters are obtained through finite volume (FVM) solution of unsteady Reynolds equations (URANS) closed by biparametric semi-empirical turbulence model. Main results. The paper demonstrates that local and integral parameters of separate blade in “hull-propeller” system are considerably different from those determined in the uniform wake at the speeds obtained for the nominal wake field in behindhull conditions. Conclusion. Krylov State Research Centre experience of numerical calculations shows that 1) in many aspects of marine hydrodynamics numerical techniques are more informative than model tests and 2) in a number of cases, conventional propeller design approach based on the nominal wake field data (calculated or experimental) might lead to somewhat incorrect technical solutions.

VALUE OF PERIODICALLY ROTATED OVERLAPPING PARALLEL LINES WITH ENHANCED RECONSTRUCTION TECHNIQUE COMPARED TO T2 WEIGHTED TURBO SPIN ECHO SEQUENCE ON ROTATOR CUFF INJURIES IN MRI SHOULDER.

Objective: The purpose of the study is to analyze the uses of conventional T2 sequences and PROPELLER technique in view of artifact reduction, increase the image quality and identify signs of pathology on shoulder magnetic resonance imaging. A total number of 36 Materials and Method: patients who underwent shoulder MRI with pain intolerance were included in the study. We used PROPELLER and without PROPELLER technology in the same participants. The MRI scans were evaluated separately by qualied musculoskeletal radiologists. Artifacts, overall image quality, and delineation of several anatomic structures were all investigated in relation to the diagnostic value of an MR arthrography examination. The signicance of propeller was analyzed by implementing Mann Whitney U test. The TSE sequences had worse pulsation artifacts and Results: better overall image quality than PROPELLER sequences. In both Coronal Oblique and Sagittal Oblique approach, delineation of all addressed anatomic structures was much better with PROPELLER sequences than with TSE. The PROPELLER approach for MRI of the Conclusion: shoulder minimizes the frequency of sequences with diagnostic impairment owing to motion artifacts and enhances picture quality when compared to traditional TSE sequences.

Comparison between the acoustic signatures of a conventional propeller and a tip-loaded propeller with winglets

The Ffowcs-Williams and Hawkings acoustic analogy is utilized to reconstruct the acoustic signature of two marine propellers with and without winglets at the tip of their blades. The database from a large-eddy simulation study is exploited and conducted on a computational grid consisting of about 5 × 109 points. The results of this study demonstrate that tip-loading of the propeller with winglets successfully improves its performance in terms of thrust and efficiency of propulsion. Meanwhile, despite the use of winglets at the tip of the propeller blades, its acoustic signature is reinforced. This result is mainly found attributable to the loading component of sound, originating from the fluctuations of hydrodynamic pressure on the surface of the propellers, in particular at their outer radii: they are significantly higher in the tip-loaded case. In contrast, the non-linear component of sound is similar between the two cases, as a result of the similarity between wake developments and instability behaviors of the structures shed by the conventional and tip-loaded propellers. However, also in this case, the sound coming from the latter is slightly higher, due to the acoustic signature of its stronger tip vortices.

Aerodynamic Analysis of Conventional and Boundary Layer Ingesting Propellers

Abstract The boundary layer ingestion (BLI) concept has emerged as a novel technology for reducing aircraft fuel consumption. Several studies designed BLI-fans for aircraft. BLI-propellers, although, have still received little attention, and the choice of open-rotors or ducted propellers is still an open question regarding the best performance. The blade design is also challenging because the BLI-propulsors ingest a nonuniform flow. These aspects emphasize further investigation of unducted and ducted BLI-propulsors and the use of optimization frameworks, coupled with computational fluid dynamics simulations, to design the propeller to adapt to the incoming flow. This paper uses a multi-objective NSGA-II optimization framework, coupled with three-dimensional RANS simulations and radial basis function (RBF) metamodeling, used for the design and optimization of three propeller configurations at cruise conditions: (a) conventional propeller operating in the freestream, (b) unducted BLI-propeller, and (c) ducted BLI-propeller, both ingesting the airframe boundary layer. The optimization results showed a significant increase in chord and a decrease in the blade angles in the BLI configurations, emphasizing that these geometric parameters optimization highly affects the BLI-blade design. The unducted BLI-propeller needs approximately 40% less shaft power than the conventional propeller to generate the same amount of propeller force. The ducted BLI-propeller needs even less power, 47%. The duct contributes to the tip vortex weakening, recovering the swirl, and turning into propeller force, as noticed from 80% of the blade span to the tip. However, the unducted and ducted BLI-configurations presented a higher backward force, 26% and 46%, respectively, compared to the conventional propeller, which can be detrimental and narrow the use of these configurations.

The study on the scaling effects in the surface piercing propeller

Surface Piercing Propellers (SPPs) are widely used in high-speed crafts. These types of propellers can work at high rotational speeds and in a turbulent environment with high efficiency. One of the most widely used methods in estimating the performance of conventional marine propellers is the use of model testing in towing tank or cavitation tunnel. These propellers' open water hydrodynamic performance can be checked in a laboratory test before being made at full scale. According to the lack of similarity between the model and the full scale in this type of propeller, the flow regime is not the same as the scale values of the model, which leads to the difference in the hydrodynamic characteristics estimate. Many scaling techniques have been created to correct the measured thrust and torque values in model scale for conventional propellers. But, SPPs operate in two different phases, and traditional scaling approaches may not be applied to these types of propellers. For this purpose, four scales of a 5-bladed SPP with available experimental data were investigated using RANS equations and applying the VOF function to the free surface. The sliding mesh technique and the K-omega turbulence model are used in grid discretization and calculation of the Reynolds stress. The numerical method was validated by the cavitation tunnel test, and the effects of scale checked by numerical estimates and conventional methods. The results of scale effects indicate that traditional approaches are unsuitable for SPPs. In detail, an examination of the pressure and shear components of the hydrodynamic coefficients shows that they are affected by the pressure component induced by ventilation pattern. Finally, the thrust, torque coefficient, and efficiency were studied by changing the Different variables and presented the results.

The dynamics of the tip vortices shed by a tip-loaded propeller with winglets

The tip vortices shed by two marine propellers are studied, relying on large-eddy simulation, using a cylindrical grid consisting of 5 billion points. A tip-loaded design, featuring winglets at the tips of its blades, is compared against a conventional one at the design advance coefficient and a model-scale Reynolds number equal to 432 000. The tip-loaded propeller achieves improved performance, but produces also more intense tip vortices. The propeller with winglets actually generates two vortices from the tip of each blade, originating at the edge of each winglet and at the junction between the winglets and the blades. They merge at a short distance downstream, within a diameter from the propeller plane. The helical vortices originating from this merging process experience a slower instability, in comparison with the tip vortices in the wake of the conventional propeller, persisting further downstream, due to the weaker shear with the wakes shed by the following blades. The results of the simulations highlight that splitting the single tip vortex of a conventional propeller into two smaller vortices by means of winglets does not imply necessarily the generation of weaker vortices and lower negative peaks of pressure at their core: the geometry of the winglets needs to be carefully optimized to achieve this target.

Research on a water-treading bionic propeller with variable pitch

Lizards living in the rainforests of the Americas can run and tread on the water surface. It was found that a lizard's feet are constantly reorienting in the water to adapt to the flow field during treading and running, thus providing greater driving forces and faster speeds than other animals with the same mass. Inspired by this, we utilized planetary gears and a crank rocker mechanism to design a water-treading paddle propeller in order to imitate the behavior of a lizard, and we also derived a mathematical model of the propeller during motion. Using FLUENT's sliding dynamic mesh technique, the water-treading and variable-pitching propeller and a conventional fixed-pitch propeller were simulated under different operating conditions. The results showed that the performance of the newly designed propeller was better than that of the conventional propeller, mainly due to the change in the blade angle of the new propeller. The front edge of the pitching propeller touched the water surface first at the moment of water entry and generated a positive thrust, while the blade's vertical exit reduced the drag. The maximum efficiency of the pitching propeller was obtained at an advance coefficient of J=1.25. Compared with the case of J=1.85, it was found that at the moment of water entry for the case of J=1.25, the large leading-edge vortex around the blade's lower surface made the thrust coefficient higher. At the moment of water exiting, a large vortex at the front of the propeller created a low-pressure area, which caused the propeller to be subject to less drag. By considering the effect of the rotation speed on the performance of the variable-pitch propeller, it was found that the efficiency at a rotational speed ω2=4πrad/s was always higher than those at ω1=0.5ω2 and ω3=2ω2, and the thrust and lift coefficients decreased with the increase in the rotation speed.

대형 캐비테이션터널에서 펌프젯 추진기 자항성능 시험 및 해석 기법 연구

In order to study the self-propulsion test and analysis techniques for the submerged body with pumpjet propulsors in the Large Cavitation Tunnel (LCT), at the Korea Research Institute of Ships and Ocean Engineering, a set of test equipment was designed and manufactured. The pumpjet propulsor is composed of rotor, stator and duct which results in the strong interaction between the components. To measure the thrust and torque for duct and stator, a ring-shaped sensor was applied. The test equipment including pumpjet is installed on the stern of the submerged body. As the whole pumpjet including duct and stator was considered as the propulsor from pumpjet open-water test, the self-propulsion test was conducted in the same way. The total thrust, combined thrust of rotor, duct and stator was used for the pumpjet self-propulsion test analysis. Accordingly, the self-propulsion test and analysis were conducted in the same way as those of the conventional propeller. The full-scale performances of the pumpjet propulsor were compared with those of the reference propeller. On the basis of the present study, it is thought that the pumpjet propulsor would be designed optimally.

Experimental and numerical investigation of hydrodynamic performance of a new surface piercing propeller family

Today, passenger and racing boats increasingly utilize surface-piercing propellers. This type of propeller operates in two distinct phases of water and air simultaneously. As a result, this propeller type has additional characteristics that must be investigated separately from conventional propellers. A new family of surface piercing propellers was investigated using experimental and numerical methods. The family consisted of five propeller models with varying geometric features operating at an immersion ratio of 0.7. Experiments were conducted in the Sharif University of Technology's hydrodynamic group's cavitation tunnel. Additionally, using Star-CCM + software, the numerical simulation was performed using the RANS method for implicit unsteady flow with a sliding mesh technique in free surface conditions. The results indicate that by increasing the pitch ratio from 1.074 to 1.61, the critical advance coefficient value, which is in the range of 0.4–0.6, moves to 0.8–1 interval. Also, the efficiency enhances by 14% while raising the pitch ratio. The amplitude of force and moment fluctuation components increases at higher than 0.5 values of the advance coefficient by increasing pitch ratios. The expanded area grows proportional to an increased number of blades and as a result, the thrust and torque coefficients increase, but the efficiency does not improve significantly. Furthermore, the fluctuation amplitude of forces and moments applied to the key blade increases up to the critical advance coefficient in all models and then decreases for above critical values.

Spherical Indoor Coandă Effect Drone (SpICED): A Spherical Blimp sUAS for Safe Indoor Use

Even as human–robot interactions become increasingly common, conventional small Unmanned Aircraft Systems (sUAS), typically multicopters, can still be unsafe for deployment in an indoor environment in close proximity to humans without significant safety precautions. This is due to their fast-spinning propellers, and lack of a fail-safe mechanism in the event of a loss of power. A blimp, a non-rigid airship filled with lighter-than-air gases is inherently safer as it ’floats’ in the air and is generally incapable of high-speed motion. The Spherical Indoor Coandă Effect Drone (SpICED), is a novel, safe spherical blimp design propelled by closed impellers utilizing the Coandă effect. Unlike a multicopter or conventional propeller blimp, the closed impellers reduce safety risks to the surrounding people and objects, allowing for SpICED to be operated in close proximity with humans and opening up the possibility of novel human–drone interactions. The design implements multiple closed-impeller rotors as propulsion units to accelerate airflow along the the surface of the spherical blimp and produce thrust by utilising the Coandă effect. A cube configuration with eight uni-directional propulsion units is presented, together with the closed-loop Proportional–Integral–Derivative (PID) controllers, and custom control mixing algorithm for position and attitude control in all three axes. A physical prototype of the propulsion unit and blimp sUAS was constructed to experimentally validate the dynamic behavior and controls in a motion-captured environment, with the experimental results compared to the side-tetra configuration with four bi-directional propulsion units as presented in our previously published conference paper. An up to 40% reduction in trajectory control error was observed in the new cube configuration, which is also capable of motion control in all six Degrees of Freedom (DoF) with additional pitch and roll control when compared to the side-tetra configuration.

Experimental investigation into the aerodynamic and aeroacoustic performance of bioinspired small-scale propeller planforms

The multi-rotors have a limited operational period and generate too much noise, which is insufficient for complex tasks and adversely affects humans’ and animals’ health. Nevertheless, their market has become increasingly popular. Therefore, low-noise products are more competitive, and aerodynamic and acoustic improvements are critical. This investigation aims to design a small bioinspired propeller with the same power input as a conventional propeller to achieve the same or better aerodynamic performance while decreasing noise. Accordingly, an experiment investigated the impacts of operation conditions and varied geometric parameters on six small propellers' aeroacoustic performances with a unique planform shape inspired by five insects and one plant seed, such as Blattodea, Hemiptera, Hymenoptera, Neuroptera, Odonata, and maple seed. Each propeller was operated at eleven rotational speeds ranging from 3000 to 8000 RPM with no freestream velocity for simulating hover conditions. Compared to the baseline propeller, the results demonstrate that all bioinspired propellers produce more thrust for the same power supply, reduce harmonic and broadband noise, and provide a better noise level. Also, their rotational speed is lower and their figure of merit is higher than the baseline propeller at hover flight with 3N thrust. They all outperform the baseline propeller in terms of hover efficiency at all thrust values considered. Besides, the Neuroptera propeller is more efficient than other propellers, decreasing 5.5 W of power and reducing 7.9 dBA at hover flight with 3N thrust and 1.5 meters distance, compared to the baseline propeller.

Numerical Investigation of the Effect of Trailing Edge Shape on Surface-Piercing Propeller Performance

One of the main challenges in the development of surface-piercing propellers is to identify the effects of geometric parameters on the performance. The main geometric difference between SPP and conventional propellers is its blade section shape. The blade section is of super cavity type with a sharp leading edge and thick trailing edge. The geometry of this propeller is mostly designed experimentally, and comprehensive studies have not been performed to examine its parameters. Therefore, this research aims to investigate the effect of trailing edge shape on ventilation cavity development and SPP performance. The performance of a series of HL-tx propellers consisting of 6 propellers with different trailing edge shapes has been studied numerically. Numerical simulation of geometries was performed using URANS method coupled with the VOF method to capture the interface of fluids. The sliding mesh technique was also used to simulate the rotation of SPPs in transition mode. The results of the simulation method are in good agreement with the experimental data. As the results indicated, there was a 40% change in thrust and torque coefficients due to the trailing edge shape changes, which is a significant effect. However, changes in efficiency are about 7%. Meanwhile, the results revealed SPPs with a larger angle to the chord line and shorter height have better performance and ventilation cover behind the blade.