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Side view of the six configurations analyzed, separated into flap nested (left) and flap deflected (right) cases.
Source publication
This paper addresses the aerodynamic performance and numerical modeling of over-the-wing propellers. Installing the propeller above a wing has the potential to increase wing lift-to-drag ratio, high-lift capabilities, and to reduce flyover noise. However, the prediction of its performance is difficult, since research on the aerodynamic interaction...
Contexts in source publication
Context 1
... simulate high-lift conditions, the maximum possible flap deflection of δ = 23 • was selected, which was limited by the geometry of the support sting. For the selected deflection angle, the values of flap gap and overlap (defined in Figure 3) were selected to be of 3.9% and 3.5% chord length respectively, based on earlier reports. Figure 3 shows the selected configurations. ...
Context 2
... the selected deflection angle, the values of flap gap and overlap (defined in Figure 3) were selected to be of 3.9% and 3.5% chord length respectively, based on earlier reports. Figure 3 shows the selected configurations. For the cruise conditions (flap nested), two axial propeller positions were evaluated: the location of maximum airfoil thickness (Configuration 1, at 35% chord) and the trailing edge of the main element (Configuration 2, at 85% chord). ...
Context 3
... second one corresponds to the position that the propeller would have attained if it were physically connected to the flap (Configuration 6). Figure 3. ...
Context 4
... simulate high-lift conditions, the maximum possible flap deflection of δ = 23 • was selected, which was limited by the geometry of the support sting. For the selected deflection angle, the values of flap gap and overlap (defined in Figure 3) were selected to be of 3.9% and 3.5% chord length respectively, based on earlier reports. Figure 3 shows the selected configurations. ...
Context 5
... the selected deflection angle, the values of flap gap and overlap (defined in Figure 3) were selected to be of 3.9% and 3.5% chord length respectively, based on earlier reports. Figure 3 shows the selected configurations. For the cruise conditions (flap nested), two axial propeller positions were evaluated: the location of maximum airfoil thickness (Configuration 1, at 35% chord) and the trailing edge of the main element (Configuration 2, at 85% chord). ...
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Citations
... Marcus [9] investigated OTW propellers for DP systems, employing a combination of experiments and low-fidelity numerical tools. The low-fidelity numerical tools encompassed non-uniform inflow, and blade-element model for the propeller, a panel method for the wing, and a vortex lattice model for the propeller slipstream. ...
... The propeller positioned above the wing yields the highest lift-to-drag ratio over the nine positions analysed. This agrees with trends reported in the literature [8,9,57], and is a result of the acceleration of the flow over the upper surface of the wing, which increases the suction. Placing the propeller at the highest position above the wing, reduces the drag force acting on the wing by preventing the wake from fully impacting on the wing. ...
This paper examines a Distributed Propulsion (DP) concept and involves CFD verification, optimisation and evaluation. The first part of the study validates the employed simulation methods using experimental data from the NASA Workshop for Integrated Propeller Prediction (WIPP) and the Folding Conformal High Lift Propeller (HLP) project, for isolated and installed cases under various conditions. Additionally, validation for rotor-rotor interactions was also conducted using the GARTEUR Action Group 26 measurements. The second part of the paper examines installed propeller configurations to identify performance differences based on their position relative to a lifting wing. The results indicate that distributed propellers with small radii interfere more with the wing, than tip-mounted, large propellers. Additionally, propeller and wing performance vary with respect to the propeller installation location. The propeller in tractor configuration showed higher efficiency than the over-the-wing (OTW) configuration by about 7%. However, results from this work showed a 2% improvement in the propeller efficiency when the OTW configuration had a pylon installed. This study also found that optimising the propeller from a tractor to OTW configuration, significantly improved the wing performance. At takeoff and landing, the Lift-to-Drag (L/D) ratio of the OTW configuration almost quadrupled, and the overall propulsive efficiency increased by about 5%. The simulations showed that the OTW configuration with different numbers of propellers, outperformed the tractor configurations with the same number of propellers. Furthermore, up to 26% improvement in lift and overall propulsive efficiency was found by introducing the DP system in the OTW configuration.
... With the development of aviation, the use of distributed electric propulsion is actively promoted. The reason for the promotion was the task of improving the aerodynamic characteristics of the aircraft [1][2]. The basic concept behind distributed propulsion is that the thrust generating components of the aircraft are now fully integrated into the vehicle's airframe. ...
The study was carried out on a model of a small-sized aircraft of the type of a flying wing, which has a V-shape in plan. The structure of the flow on the wing surface was studied depending on the angle of attack and deflection of the controls. Experiments were carried out to study the influence of the work of the distributed electric propulsion on the flow structure on the wing surface. As a result, flow patterns were obtained using the “soot-oil” visualization method for each flow regime.
... They concluded that distributed high-lift propellers could enhance lift at low speeds by accelerating airflow over the wing and retracting against the nacelle during high-speed flight to minimize drag. Veldhuis et al. [10] analyzed the aerodynamic performance of a single propeller positioned over the wing using numerical methods corroborated with wind tunnel validation. They identified bilateral aerodynamic coupling between the propeller and the wing. ...
Distributed electric propulsion technology has great potential and advantages in the development of drones. In this paper, to study the slipstream effect of distributed propellers, the actuator disk method was used to verify a single propeller, and the calculated thrust was in good agreement with the test results. Then, based on the actuator disk method, the influence of different installation positions on the slipstream effect was studied, and the distributed propeller layout was optimized by a genetic algorithm to improve the low-speed performance of the unmanned aerial vehicle (UAV) during the take-off phase and increase the cruise duration. The analysis results showed that the lift of the wing will be larger when the propellers are higher than the wing. The wing lift and drag of the counter-rotating are less than those of the co-rotating. Compared with the original layout, the lift coefficient of the optimized distributed propeller layout is significantly increased by 30.97%, while the lift/drag ratio is increased by 7.34%. Finally, we designed the test platform and qualitatively verified the calculated results without quantitative verification.
... A lift increase of 8% for the OTW propeller has been shown, caused by both a lift increase and drag reduction compared to the isolated configuration [16]. This lift increase has shown to be sensitive to the chordwise position of the propeller, in which a propeller closer to the trailing edge gave the largest effect on the lift production [20]. ...
... The intrinsic characteristics of electric motors make them suitable for aeronautical propulsion. These characteristics are not limited to high efficiency, reduced volume, low weight, power independence with altitude, and the ability to scale over a wide range of sizes without loss of efficiency or power-to-weight ratio (COLE, 2016;KIM;PERRY;ANSELL, 2018;MARCUS et al., 2018;GERMAN, 2016). Electric motors also enable new degrees of freedom for aircraft designers to position the engines to obtain a better aeropropulsive integration in such a way that the efficiency of the set is greater than the sum of the individual efficiencies (COLE, 2016;KIM;PERRY;ANSELL, 2018;MARCUS et al., 2018;GERMAN, 2016). ...
... These characteristics are not limited to high efficiency, reduced volume, low weight, power independence with altitude, and the ability to scale over a wide range of sizes without loss of efficiency or power-to-weight ratio (COLE, 2016;KIM;PERRY;ANSELL, 2018;MARCUS et al., 2018;GERMAN, 2016). Electric motors also enable new degrees of freedom for aircraft designers to position the engines to obtain a better aeropropulsive integration in such a way that the efficiency of the set is greater than the sum of the individual efficiencies (COLE, 2016;KIM;PERRY;ANSELL, 2018;MARCUS et al., 2018;GERMAN, 2016). ...
... Besides, it allows the implementation of differential thrust for yaw and roll control, allowing the size reduction of control surfaces and, consequently, reducing drag (DELBECQ et al., 2022). Furthermore, the use of electric motors allows a decoupling between the power source and the propulsive device, allowing both to operate independently at their respective optimal points (KIM; PERRY; ANSELL, 2018;MARCUS et al., 2018). Such technological advantages of DEP make it one of the possible solutions to reach the decarbonisation goals of aviation by 2050, established in 2021 by the air transport stakeholders ( The UAM vehicles are expected to operate in densely populated regions at low altitudes, exposing a significant portion of the population to the noise generated by them (INGRAHAM; GRAY; LOPES, 2019; INTERNATIONAL CIVIL AVIATION ORGANI -ZATION, 2022). ...
The development of electric motors and batteries for aeronautical applications should soon allow the design of aircraft that benefit from better propulsion-airframe integration. These new aircraft must be able to take advantage of the synergistic effects of this integration that were previously not possible with heavy combustion engines. One of these new concepts made possible by electric motors is the so-called wingtip-mounted propellers. The advantage of this engine positioning is that the propeller's slipstream rotating in a direction opposed to the wingtip vortex allows the reduction of the induced drag, in addition to an increase in the propeller's efficiency due to the swirl recovery promoted by the wing. It is necessary to know how the design parameters affect these aircraft's aero-propulsive and aeroacoustic performance to allow a better exploration of these concepts in the early stages of aircraft design. In this context, the research presented in this thesis refers to the design and implementation of a test rig at the Department of Aeronautical Engineering at EESC-USP for aerodynamic and aeroacoustic tests of distributed electric propulsion (DEP) aircraft wings. In addition, the aerodynamic forces and the noise generated by different combinations of propeller installation positions about the leading edge and chord-span plane, flap, and aileron deflections were measured in wind tunnels. In general, the propellers installed below the wing chord line allowed a more significant reduction of the induced drag factor (up to 25.7% about the corresponding condition without the propeller). The wingtip-mounted propeller mounted also increased the effectiveness of the aileron by up to 57% (for negative aileron deflections) and up to 75% (for positive aileron deflections), practically keeping the effectiveness of the flap unchanged, which was outside of the propeller stream tube. Regarding the acoustic measurements, the results showed that broadband noise was practically independent of the installation position of the propeller, which was not observed for the tonal noise, whose intensity and directivity pattern was highly dependent on the propeller installation position.
... This agrees with trends reported in the literature (Refs. [35][36][37], and is a result of the acceleration of the flow over the wing's upper surface, which increases the suction. Placing the propeller at the highest position above the wing reduces the drag force acting on the wing by preventing the wake from fully impacting the wing. ...
The study presented in this paper focuses on distributed propulsion concepts and involves CFD verification and optimization. The first part of the study validates experimental data from the NASA Workshop for Integrated Propeller Prediction (WIPP) and the folding conformal high lift propeller projects by comparing them with high-fidelity CFD results from HMB3 for both isolated and installed configurations at different forward flight speeds. The second part of the paper examines various propeller installed configurations to identify performance differences based on their position relative to the lifting wing, similar to those used in modern eVTOL designs. The results show that distributed propellers with small radii interfere more strongly with the wing than tip-mounted propellers. Furthermore, the propeller's position relative to the wing affects its performance, with propellers placed ahead of the leading edge showing better performance than those placed on top of the wing. As RPM increases to operate at high-performance conditions, the propeller from the tractor configuration experiences a slightly reduction in efficiency, whereas the performance loss of the propeller from over-wing configuration becomes much less. The study also finds that optimizing the propeller from a traditional tractor configuration to a novel over-wing configuration significantly improves the performance of the wing, particularly during take-off and landing conditions.
... An overview of the experimental setup used in the wind-tunnel tests, performed in the DNW Low-Speed Tunnel (LST), is shown in Fig. 2. In these tests, the effect of three propellers placed above a rectangular wing was quantified using an external balance and pressure taps. The wing model had a chord of c = 0.3 m and a span of b = 1.25 m, and featured an NLF-MOD22B airfoil [30,31]. Three XPROP-S propellers (D P = 0.2032) were installed on a support sting on the suction side of the wing. ...
... The values obtained at the bounds of the aerodynamic model are also applied to the flight-performance constraints that are performed with the flap deflected (take-off, approach, and balked landing). This is again considered a conservative approach, since earlier research has shown that an OTW propeller can postpone flow separation [18,19] and reduce the pressure drag [31] in the case of flap deflection, if the system is properly designed. Although these simplifying assumptions could not be verified within the scope of this research due to the sensitivity of high-lift performance to the Reynolds number and specific design of the high-lift system, they should be revisited once a more detailed investigation of the high-lift characteristics has been performed. ...
... Now that the approximate location and extent of the two propulsor systems has been presented, the size and axial position of the OTW propellers has to be decided. Earlier research has shown that the lift-to-drag ratio benefit is higher for propellers placed near the location of maximum airfoil thickness [16,20,31,51]. However, for forward locations, the propulsive efficiency of the propellers is reduced considerably [20,31]. ...
The goal of this study is to analyze how the aeropropulsive benefits of an over-the-wing distributed-propulsion (OTWDP) system at the component level translate into an aeropropulsive benefit at the aircraft level, as well as to determine whether this enhancement is sufficient to lead to a reduction in overall energy consumption. For this, the preliminary sizing of a partial-turboelectric regional passenger aircraft is performed, and its performance metrics are compared to a conventional twin-turboprop reference for the 2035 timeframe. The changes in lift, drag, and propulsive efficiency due to the OTWDP system are estimated for a simplified unducted geometry using a lower-order numerical method, which is validated with experimental data. For a typical cruise condition and the baseline geometry evaluated in the experiment, the numerical method estimates a 45% increase in the local sectional lift-to-drag ratio of the wing, at the expense of a 12% reduction in propeller efficiency. For an aircraft with 53% of the wingspan covered by the OTWDP system, this aerodynamic coupling is found to increase the average aeropropulsive efficiency of the aircraft by 9% for a 1500 n mile mission. Approximately 4% of this benefit is required to offset the losses in the electrical drivetrain. The reduction in fuel weight compensates for the increase in powertrain weight, leading to a takeoff mass comparable to the reference aircraft. Overall, a 5% reduction in energy consumption is found, albeit with a [Formula: see text] uncertainty due to uncertainty in the aerodynamic modeling alone.
... However, the available literature mainly concerns hovering conditions, whereas the aeroacoustic interaction effects in forward-flight remains relatively unexplored. Besides, although isolated multi-propeller systems or wing-mounted single rotors have been extensively investigated [18][19][20][21][22], installation effects on multi-rotor configurations have not been deeply examined so far. In particular, some studies regarding the aerodynamics of these configurations are available in the literature [3], whereas their acoustics remains relatively unexplored. ...
This paper presents a numerical investigation of noise radiated by two side-by-side propellers, suitable for Distributed-Electric-Propulsion concepts. The focus is on the assessment of the variation of the effects of blade tip Mach number on the radiated noise for variations of the direction of rotation, hub relative position, and the relative phase angle between the propeller blades. The aerodynamic analysis is performed through a potential-flow-based boundary integral formulation, which is able to model severe body–wake interactions.The noise field is evaluated through a boundary-integral formulation for the solution of the Ffowcs Williams and Hawkings equation. The numerical investigation shows that: the blade tip Mach number strongly affects the magnitude and directivity of the radiated noise; the increase of the tip-clearance increases the spatial frequency of
the noise directivity at the two analyzed tip Mach numbers for both co-rotating and counter-rotating configurations; for counter-rotating propellers, the relative phase angle between the propeller blades provides a decrease of the averaged emitted noise, regardless the tip Mach number. One of the main results achieved is the scalability with the blade tip Mach number of the influence on the emitted noise of the considered design parameters.
... Inherent characteristics of electric motors, such as high efficiency, reduced volume, low weight, power independence to altitude, and the ability to scale over a wide range of sizes without loss of efficiency or weight-power ratio make electric motors suitable for aeronautical propulsion [1,2,3,4]. In addition, electric motors allow new degrees of freedom for aeronautical designers to position the engines to obtain better aeropropulsive integration, in such a way that the efficiency of the set is greater than the sum of the individual efficiencies [1,2,3,4]. ...
... Inherent characteristics of electric motors, such as high efficiency, reduced volume, low weight, power independence to altitude, and the ability to scale over a wide range of sizes without loss of efficiency or weight-power ratio make electric motors suitable for aeronautical propulsion [1,2,3,4]. In addition, electric motors allow new degrees of freedom for aeronautical designers to position the engines to obtain better aeropropulsive integration, in such a way that the efficiency of the set is greater than the sum of the individual efficiencies [1,2,3,4]. Traditionally, however, propellers and wings are designed independently, since the interactions between them are quite complex [5,6,7]. During the conceptual design phase of both, the aerodynamic interactions between propellers and wing and between propellers are not well modeled (only empirical corrections of installation effects can be made) [7]. ...
The aerodynamic and aeroacoustic interaction effects between propellers and between propellers and wing are being investigated experimentally in a wind tunnel at the Department of Aeronautical Engineering of the University of São Paulo (Brazil). The results will bring a better understanding of these interactions, which will allow the elaboration of good practices for distributed electric propulsion conceptual designs, and provide a database for validating computational tools. The experimental setup, methods, and some preliminary acoustic results are shown in this paper.
... Hongbo Wang [8,9] investigated several layouts for distributed multi-propeller configuration including OTWP configuration and channel wing, and he studied the influence of the propeller locations in 2016. Marcus [10] tested several OTWP model in a wind tunnel in 2018. His models included a Fowler flap and an over-wing propeller with different chordwise locations and inclination angles. ...
... The wingspan was l = 1.52 m, wing area S = 0.76 m 2 , wing chord c = 0.5 m, and the propeller was located above the wing at 0.5c, surrounded 120 • by the channel wing. Hongbo Wang [8,9] and Marcus [10] have studied the effect of the position of the propeller, so this paper will not focus on the effect of the position of the propeller. To study the interaction between the propeller and the wing, ensure that the propeller and the wing have sufficient interference space, and the flow field before and after the propeller can develop with the coupling of the wing, in this paper, it was decided that the propeller would be placed at 0.5c of the wing. ...
Channel wing is a propeller-coupling layout that has good low-speed performance and S/VTOL potential. Focused on the application of this layout at the S/VTOL stage, this paper attempts to find the interaction mechanism for the distributed propeller channel wing. Firstly, the computation method based on RANS equations for propeller–wing integration was established with Momentum Source Method, which was compared with the unsteady Sliding Mesh method and validated by a ducted propeller. Secondly, the performances and aerodynamic characteristics of the single-propeller channel wings with two different airfoils were analyzed, and a ground test for the scaled model was conducted. Finally, a four-propeller channel wing was analyzed and compared with single-propeller channel wing, then the flow field characteristics were discussed in depth. The study shows that the airfoil shape will strongly affect the lift of channel wing at S/VTOL stage. Multi-propeller channel wing analysis indicates that rotational direction plays an important role in outside propeller interaction, where outboard-up rotation increases outside channel lift. In addition, the propeller wake also shows special distortion and dissipation behaviors, which are strongly affected by adjacent propellers.
