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Isometric (left), top (middle) and front (right) views of the wind tunnel setup, including component designation, coordinate system and direction of rotation of the propeller. All dimensions are in mm.
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
... order to simulate an OTW propeller configuration, a propeller was positioned on the suction side of a wing mounted vertically in the wind-tunnel test section, as depicted in Figures 1 and 2. The wing spanned the full height of the test section and was placed on a turntable, which could be rotated to change the angle of attack. ...
Context 2
... The airfoil presents a maximum thickness-to-chord ratio of 0.17 at 35% chord and a fowler flap of 30% chord length. The main dimensions are indicated in Figure 1. The four-bladed propeller model has a diameter of D P = 0.237 m (D P /c = 0.395), a blade chord of 7.8% of the propeller diameter, and a pitch angle of 23 • at 75% of the propeller radius. ...
Context 3
... detailed information regarding the propeller geometry can be found in the work of Sinnige et al. 22 The propeller was driven by a 7.5 hp three-phase induction motor housed in a nacelle of 0.07 m diameter, positioned by means of a support sting which could be traversed along all three axes. The support sting was installed under a small inclination angle as depicted in Figure 1, in order to position the propeller axis at the spanwise location of the pressure ports (see Section II.B) when the traverse mechanism was set at its neutral position along the Y-axis. ...
Context 4
... order to obtain the surface pressure distribution, the wing model featured 54 static pressure ports on the main element and 27 on the flap, distributed over the pressure and suction sides. The ports were located along a zigzag path extending over a spanwise interval of 100 mm, as indicated in Figure 1. For each configuration, the propeller was traversed in spanwise direction to resolve the wing pressure distribution, covering a span of 1.5D P . ...
Context 5
... Configuration 1, on the other hand, local changes in transition location were observed. These observations are shown in Figure 10. In the propeller-off case of Configuration 1 (Figure 10a), the transition location moved aft due to the favorable pressure gradient generated by the nacelle. ...
Context 6
... observations are shown in Figure 10. In the propeller-off case of Configuration 1 (Figure 10a), the transition location moved aft due to the favorable pressure gradient generated by the nacelle. However, with the propeller operating ahead of the transition line (Figure 10), the transition location moved forward. ...
Context 7
... the propeller-off case of Configuration 1 (Figure 10a), the transition location moved aft due to the favorable pressure gradient generated by the nacelle. However, with the propeller operating ahead of the transition line (Figure 10), the transition location moved forward. There are two reasons for this. ...
Context 8
... discussed earlier, the primary interest of this study lies in the effect of the propeller, and not of the installation elements. Accordingly, Figure 11 shows the lift and drag coefficients as a difference between propeller-off and propeller-on conditions. Evidently, wing lift increased with decreasing advance ratio (increased thrust). ...
Context 9
... Configuration 1 the wind tunnel measurements at J = 0.9 present a lower lift coefficient than with the propeller off, due to local windmilling of the blades close to the wing surface. This was reflected in wing pressure distributions, which in these cases presented increased pressure ahead of the propeller disk, contrary to the behavior observed in Figure 9. Regarding the pressure drag of the wing, Figure 11 shows that it decreased with decreasing advance ratio for Configuration 1. This is due to increased suction ahead of the thickest point of the wing. ...
Context 10
... total-pressure distributions in the propeller disk plane and wake plane, obtained from the numerical model and experimental setup respectively, are shown in Figure 12. By comparing Figures 12a and 12c to 12b and 12d, it can be observed how the highly-loaded region in the wake plane has turned in clockwise direction due to the propeller-induced swirl, increasing in magnitude and concentrating over a smaller region due to contraction. ...
Context 11
... total-pressure distributions in the propeller disk plane and wake plane, obtained from the numerical model and experimental setup respectively, are shown in Figure 12. By comparing Figures 12a and 12c to 12b and 12d, it can be observed how the highly-loaded region in the wake plane has turned in clockwise direction due to the propeller-induced swirl, increasing in magnitude and concentrating over a smaller region due to contraction. In the wake plane (Figures 12b and 12d), the decreased total pressure in the wake of the support sting, nacelle and wing can be clearly distinguished. ...
Context 12
... comparing Figures 12a and 12c to 12b and 12d, it can be observed how the highly-loaded region in the wake plane has turned in clockwise direction due to the propeller-induced swirl, increasing in magnitude and concentrating over a smaller region due to contraction. In the wake plane (Figures 12b and 12d), the decreased total pressure in the wake of the support sting, nacelle and wing can be clearly distinguished. Furthermore, the propeller slipstream is deformed and displaced in vertical direction due to the downwash of the wing. ...
Context 13
... the propeller slipstream is deformed and displaced in vertical direction due to the downwash of the wing. Two important effects are observed in Figure 12. Firstly, less thrust was generated than in the isolated- propeller case in both cruise configurations, due to increased velocities above the wing. ...
Context 14
... less thrust was generated than in the isolated- propeller case in both cruise configurations, due to increased velocities above the wing. This was confirmed by comparing the total pressure distributions in Figures 12a and 12c to the isolated propeller values in Figure 8. The thrust reduction was more pronounced in Configuration 1, since on the forward part of the airfoil the velocity increase generated by the wing was higher, and thus the effective advance ratio of the propeller was increased more than in Configuration 2. Secondly, the non-uniform inflow conditions led to azimuthal loading variations in both configurations. ...
Context 15
... pressure-coefficient distributions on the wing, ∆C p , are presented in Figure 13 for high-lift Configurations 3 to 6 at advance ratio J = 0.7. Again, wing pressures were decreased and increased in front of and behind the propeller respectively, except in Configuration 3. In this configuration, the effective advance ratio was exceptionally high and, accordingly, propeller effects on the wing were weak. ...
Context 16
... pressure variations became even more prominent in Configuration 6, due to an improved alignment between the propeller axis and the local flow direction and reduced distance between the flap surface and the propeller. Strips of increased pressure can be observed in Figure 13 on the suction side at x/c = 0.3 for all configurations. IR images revealed that this location corresponded to the chordwise location of boundary-layer transition. ...
Context 17
... to the previous section, Table 3 contains the isolated wing and propeller-off lift and drag coefficients, for reference. Figure 14 shows the lift and drag coefficients as a difference between propeller-on Figure 14a indicates an increase in lift with decreasing advance ratio, comparable to the effect seen for cruise configurations. From Figure 14 it is evident that at high advance ratios, the propeller was operating in windmilling conditions close to the wing surface, leading to decreased lift and increased pressure drag. ...
Context 18
... to the previous section, Table 3 contains the isolated wing and propeller-off lift and drag coefficients, for reference. Figure 14 shows the lift and drag coefficients as a difference between propeller-on Figure 14a indicates an increase in lift with decreasing advance ratio, comparable to the effect seen for cruise configurations. From Figure 14 it is evident that at high advance ratios, the propeller was operating in windmilling conditions close to the wing surface, leading to decreased lift and increased pressure drag. ...
Context 19
... 14 shows the lift and drag coefficients as a difference between propeller-on Figure 14a indicates an increase in lift with decreasing advance ratio, comparable to the effect seen for cruise configurations. From Figure 14 it is evident that at high advance ratios, the propeller was operating in windmilling conditions close to the wing surface, leading to decreased lift and increased pressure drag. This effect was confirmed with the wake-plane pressure distributions (see Section IV.B.2), and was more pronounced in Configuration 3 due to the large inflow velocities perceived by the propeller towards the leading edge of the wing. ...
Context 20
... of the total pressure measurements in the wake plane for the climb configurations are shown in Figure 15 at J = 0.7. Additional wake-plane results showed that, in for example Configuration 3, J = 0.8, the total pressure coefficients in the slipstream were lower than in the freestream, indicating that the propeller was extracting energy from the flow over the complete disk. ...
Context 21
... implies that in Configuration 3 the propeller was windmilling for advance ratios above 0.8, even though the isolated propeller generated thrust up till J = 1 (see Figure 8). This explains the lift decrease observed in Figure 14. Since flow velocities above the wing decrease as the distance to the wing surface increases, in some cases only the bottom fraction of the propeller was windmilling, while the top part, which had a lower effective advance ratio, was generating thrust, as reflected in Figure 15a. ...
Context 22
... explains the lift decrease observed in Figure 14. Since flow velocities above the wing decrease as the distance to the wing surface increases, in some cases only the bottom fraction of the propeller was windmilling, while the top part, which had a lower effective advance ratio, was generating thrust, as reflected in Figure 15a. For the same reason, when comparing Figures 12c, 15a and 15b, it can be seen that the thrust was reduced more in Configuration 3 than in Configurations 1 and 4, since the flow velocities above the wing were higher with the flap deflected and at 35% instead of 85% chord-length. ...
Context 23
... flow velocities above the wing decrease as the distance to the wing surface increases, in some cases only the bottom fraction of the propeller was windmilling, while the top part, which had a lower effective advance ratio, was generating thrust, as reflected in Figure 15a. For the same reason, when comparing Figures 12c, 15a and 15b, it can be seen that the thrust was reduced more in Configuration 3 than in Configurations 1 and 4, since the flow velocities above the wing were higher with the flap deflected and at 35% instead of 85% chord-length. ...
Context 24
... Figure 15c (Configuration 4), the up-going blade presents higher loading than the down-going blade. This is due to the downward-oriented wing-induced velocities, which follow the local inclination of the airfoil surface. ...
Context 25
... parameter is difficult to vary experimentally, whereas it is easily changed in the numerical model. To this end, Figure 17 presents ∆C L , ∆C Dp , and ∆η/η iso versus the propeller diameter, expressed as a fraction of the wing chord. The diameter of the nacelle was scaled linearly with propeller diameter. ...
Context 26
... diameter of the nacelle was scaled linearly with propeller diameter. Based on the results of Figure 16, an axial position of x p /c = 0.95 was selected. The lower bound of the diameter interval was limited by the tip Mach number, which increases considerably for smaller propellers if they have to produce large T * C values. Figure 17 shows that, within the interval studied, the propeller diameter has less effect on the three parameters than the axial position of the propeller. ...
Context 27
... lower bound of the diameter interval was limited by the tip Mach number, which increases considerably for smaller propellers if they have to produce large T * C values. Figure 17 shows that, within the interval studied, the propeller diameter has less effect on the three parameters than the axial position of the propeller. Nonetheless, it can be seen that wing lift and propeller efficiency are increased as the propeller diameter is reduced, while pressure drag is practically unchanged. ...
Context 28
... this case, the isolated propeller efficiency remains constant, and the installed propeller efficiency is increased as its diameter is reduced. Note that the previous conclusion is valid specifically for the axial position considered in Figure 17, x P /c = 0.95. Close to the trailing edge, the velocity gradient at the propeller disk is relatively small, and the inflow angle has a positive effect on propeller efficiency. ...
Context 29
... order to simulate an OTW propeller configuration, a propeller was positioned on the suction side of a wing mounted vertically in the wind-tunnel test section, as depicted in Figures 1 and 2. The wing spanned the full height of the test section and was placed on a turntable, which could be rotated to change the angle of attack. ...
Context 30
... The airfoil presents a maximum thickness-to-chord ratio of 0.17 at 35% chord and a fowler flap of 30% chord length. The main dimensions are indicated in Figure 1. The four-bladed propeller model has a diameter of D P = 0.237 m (D P /c = 0.395), a blade chord of 7.8% of the propeller diameter, and a pitch angle of 23 • at 75% of the propeller radius. ...
Context 31
... detailed information regarding the propeller geometry can be found in the work of Sinnige et al. 22 The propeller was driven by a 7.5 hp three-phase induction motor housed in a nacelle of 0.07 m diameter, positioned by means of a support sting which could be traversed along all three axes. The support sting was installed under a small inclination angle as depicted in Figure 1, in order to position the propeller axis at the spanwise location of the pressure ports (see Section II.B) when the traverse mechanism was set at its neutral position along the Y-axis. ...
Context 32
... order to obtain the surface pressure distribution, the wing model featured 54 static pressure ports on the main element and 27 on the flap, distributed over the pressure and suction sides. The ports were located along a zigzag path extending over a spanwise interval of 100 mm, as indicated in Figure 1. For each configuration, the propeller was traversed in spanwise direction to resolve the wing pressure distribution, covering a span of 1.5D P . ...
Context 33
... Configuration 1, on the other hand, local changes in transition location were observed. These observations are shown in Figure 10. In the propeller-off case of Configuration 1 (Figure 10a), the transition location moved aft due to the favorable pressure gradient generated by the nacelle. ...
Context 34
... observations are shown in Figure 10. In the propeller-off case of Configuration 1 (Figure 10a), the transition location moved aft due to the favorable pressure gradient generated by the nacelle. However, with the propeller operating ahead of the transition line (Figure 10), the transition location moved forward. ...
Context 35
... the propeller-off case of Configuration 1 (Figure 10a), the transition location moved aft due to the favorable pressure gradient generated by the nacelle. However, with the propeller operating ahead of the transition line (Figure 10), the transition location moved forward. There are two reasons for this. ...
Context 36
... discussed earlier, the primary interest of this study lies in the effect of the propeller, and not of the installation elements. Accordingly, Figure 11 shows the lift and drag coefficients as a difference between propeller-off and propeller-on conditions. Evidently, wing lift increased with decreasing advance ratio (increased thrust). ...
Context 37
... Configuration 1 the wind tunnel measurements at J = 0.9 present a lower lift coefficient than with the propeller off, due to local windmilling of the blades close to the wing surface. This was reflected in wing pressure distributions, which in these cases presented increased pressure ahead of the propeller disk, contrary to the behavior observed in Figure 9. Regarding the pressure drag of the wing, Figure 11 shows that it decreased with decreasing advance ratio for Configuration 1. This is due to increased suction ahead of the thickest point of the wing. ...
Context 38
... total-pressure distributions in the propeller disk plane and wake plane, obtained from the numerical model and experimental setup respectively, are shown in Figure 12. By comparing Figures 12a and 12c to 12b and 12d, it can be observed how the highly-loaded region in the wake plane has turned in clockwise direction due to the propeller-induced swirl, increasing in magnitude and concentrating over a smaller region due to contraction. ...
Context 39
... total-pressure distributions in the propeller disk plane and wake plane, obtained from the numerical model and experimental setup respectively, are shown in Figure 12. By comparing Figures 12a and 12c to 12b and 12d, it can be observed how the highly-loaded region in the wake plane has turned in clockwise direction due to the propeller-induced swirl, increasing in magnitude and concentrating over a smaller region due to contraction. In the wake plane (Figures 12b and 12d), the decreased total pressure in the wake of the support sting, nacelle and wing can be clearly distinguished. ...
Context 40
... comparing Figures 12a and 12c to 12b and 12d, it can be observed how the highly-loaded region in the wake plane has turned in clockwise direction due to the propeller-induced swirl, increasing in magnitude and concentrating over a smaller region due to contraction. In the wake plane (Figures 12b and 12d), the decreased total pressure in the wake of the support sting, nacelle and wing can be clearly distinguished. Furthermore, the propeller slipstream is deformed and displaced in vertical direction due to the downwash of the wing. ...
Context 41
... the propeller slipstream is deformed and displaced in vertical direction due to the downwash of the wing. Two important effects are observed in Figure 12. Firstly, less thrust was generated than in the isolated- propeller case in both cruise configurations, due to increased velocities above the wing. ...
Context 42
... less thrust was generated than in the isolated- propeller case in both cruise configurations, due to increased velocities above the wing. This was confirmed by comparing the total pressure distributions in Figures 12a and 12c to the isolated propeller values in Figure 8. The thrust reduction was more pronounced in Configuration 1, since on the forward part of the airfoil the velocity increase generated by the wing was higher, and thus the effective advance ratio of the propeller was increased more than in Configuration 2. Secondly, the non-uniform inflow conditions led to azimuthal loading variations in both configurations. ...
Context 43
... pressure-coefficient distributions on the wing, ∆C p , are presented in Figure 13 for high-lift Configurations 3 to 6 at advance ratio J = 0.7. Again, wing pressures were decreased and increased in front of and behind the propeller respectively, except in Configuration 3. In this configuration, the effective advance ratio was exceptionally high and, accordingly, propeller effects on the wing were weak. ...
Context 44
... pressure variations became even more prominent in Configuration 6, due to an improved alignment between the propeller axis and the local flow direction and reduced distance between the flap surface and the propeller. Strips of increased pressure can be observed in Figure 13 on the suction side at x/c = 0.3 for all configurations. IR images revealed that this location corresponded to the chordwise location of boundary-layer transition. ...
Context 45
... to the previous section, Table 3 contains the isolated wing and propeller-off lift and drag coefficients, for reference. Figure 14 shows the lift and drag coefficients as a difference between propeller-on Figure 14a indicates an increase in lift with decreasing advance ratio, comparable to the effect seen for cruise configurations. From Figure 14 it is evident that at high advance ratios, the propeller was operating in windmilling conditions close to the wing surface, leading to decreased lift and increased pressure drag. ...
Context 46
... to the previous section, Table 3 contains the isolated wing and propeller-off lift and drag coefficients, for reference. Figure 14 shows the lift and drag coefficients as a difference between propeller-on Figure 14a indicates an increase in lift with decreasing advance ratio, comparable to the effect seen for cruise configurations. From Figure 14 it is evident that at high advance ratios, the propeller was operating in windmilling conditions close to the wing surface, leading to decreased lift and increased pressure drag. ...
Context 47
... 14 shows the lift and drag coefficients as a difference between propeller-on Figure 14a indicates an increase in lift with decreasing advance ratio, comparable to the effect seen for cruise configurations. From Figure 14 it is evident that at high advance ratios, the propeller was operating in windmilling conditions close to the wing surface, leading to decreased lift and increased pressure drag. This effect was confirmed with the wake-plane pressure distributions (see Section IV.B.2), and was more pronounced in Configuration 3 due to the large inflow velocities perceived by the propeller towards the leading edge of the wing. ...
Context 48
... of the total pressure measurements in the wake plane for the climb configurations are shown in Figure 15 at J = 0.7. Additional wake-plane results showed that, in for example Configuration 3, J = 0.8, the total pressure coefficients in the slipstream were lower than in the freestream, indicating that the propeller was extracting energy from the flow over the complete disk. ...
Context 49
... implies that in Configuration 3 the propeller was windmilling for advance ratios above 0.8, even though the isolated propeller generated thrust up till J = 1 (see Figure 8). This explains the lift decrease observed in Figure 14. Since flow velocities above the wing decrease as the distance to the wing surface increases, in some cases only the bottom fraction of the propeller was windmilling, while the top part, which had a lower effective advance ratio, was generating thrust, as reflected in Figure 15a. ...
Context 50
... explains the lift decrease observed in Figure 14. Since flow velocities above the wing decrease as the distance to the wing surface increases, in some cases only the bottom fraction of the propeller was windmilling, while the top part, which had a lower effective advance ratio, was generating thrust, as reflected in Figure 15a. For the same reason, when comparing Figures 12c, 15a and 15b, it can be seen that the thrust was reduced more in Configuration 3 than in Configurations 1 and 4, since the flow velocities above the wing were higher with the flap deflected and at 35% instead of 85% chord-length. ...
Context 51
... flow velocities above the wing decrease as the distance to the wing surface increases, in some cases only the bottom fraction of the propeller was windmilling, while the top part, which had a lower effective advance ratio, was generating thrust, as reflected in Figure 15a. For the same reason, when comparing Figures 12c, 15a and 15b, it can be seen that the thrust was reduced more in Configuration 3 than in Configurations 1 and 4, since the flow velocities above the wing were higher with the flap deflected and at 35% instead of 85% chord-length. ...
Context 52
... Figure 15c (Configuration 4), the up-going blade presents higher loading than the down-going blade. This is due to the downward-oriented wing-induced velocities, which follow the local inclination of the airfoil surface. ...
Context 53
... parameter is difficult to vary experimentally, whereas it is easily changed in the numerical model. To this end, Figure 17 presents ∆C L , ∆C Dp , and ∆η/η iso versus the propeller diameter, expressed as a fraction of the wing chord. The diameter of the nacelle was scaled linearly with propeller diameter. ...
Context 54
... diameter of the nacelle was scaled linearly with propeller diameter. Based on the results of Figure 16, an axial position of x p /c = 0.95 was selected. The lower bound of the diameter interval was limited by the tip Mach number, which increases considerably for smaller propellers if they have to produce large T * C values. Figure 17 shows that, within the interval studied, the propeller diameter has less effect on the three parameters than the axial position of the propeller. ...
Context 55
... lower bound of the diameter interval was limited by the tip Mach number, which increases considerably for smaller propellers if they have to produce large T * C values. Figure 17 shows that, within the interval studied, the propeller diameter has less effect on the three parameters than the axial position of the propeller. Nonetheless, it can be seen that wing lift and propeller efficiency are increased as the propeller diameter is reduced, while pressure drag is practically unchanged. ...
Context 56
... this case, the isolated propeller efficiency remains constant, and the installed propeller efficiency is increased as its diameter is reduced. Note that the previous conclusion is valid specifically for the axial position considered in Figure 17, x P /c = 0.95. Close to the trailing edge, the velocity gradient at the propeller disk is relatively small, and the inflow angle has a positive effect on propeller efficiency. ...
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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.
