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The aerodynamic characteristics of turboprop aircraft are greatly affected by the running propellers. In this paper, propeller slipstream effects on the static lateral-directional stability characteristics of a typical twin-engine turboprop aircraft with clockwise rotating propellers were investigated through unsteady computational fluid dynamics (...
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... two propellers rotate clockwise (looking from the rear fuselage), which is similar to the ATR72 and Dash8-Q400. As shown in Figure 1, the takeoff configuration of the aircraft that is discussed in this paper consists of the fuselage, empennages, nacelles, propellers, and wings, which include high lift systems and the flap track fairings. ...
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... validation is carried out by comparing the calculated time-averaged pressure coefficient distributions with the measured data on the wing, HTP, and VTP at various sideslip angles. In Figures 10, 11 and 12, C p represents the pressure coefficient, η represents the dimensionless span location. For the selected wing sections, a good agreement between the computational and experimental results is observed. ...
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... power effects on the local angle of attack and stagnation pressure are correctly predicted. Figure 11 shows that the selected HTP sections exhibits some differences between the CFD simulations and wind tunnel measurements. However, the HTP has limited influences on both the lateral and directional static stability. ...
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... the HTP has limited influences on both the lateral and directional static stability. As shown in Figure 12, the suction peaks for the selected VTP sections are generally underestimated, which indicates that the local sideslip angle at the VTP is underestimated. This may be partly caused by the wind tunnel wall wasn't taken into account in the computations, and partly by discrepancies in the predicted propeller wakes due to the strong dissipative terms of the RANS model. ...
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... most of the previous studies, the effects of the propeller slipstream on the lateral static stability were only considered to be the results of rolling moments due to the sideslip-induced lateral displacement of the portion of the wing immersed in the propeller slipstream (Obert, 2009;Wolowicz & Yancey, 1972), which generally results in a decrease in the lateral static stability derivative. As shown in Figure 13(b), the negative rolling moment curve slope of the WBN, which represents the lateral static stability contribution of the WBN, is indeed smaller for the power-on configuration than for the power-off configuration in the tested range of sideslip angels. However, it can be found in Figure 13(a) that the lateral stability of the power-on configuration is not always smaller than that of the power-off configuration when the magnitude of the sideslip angle is greater than 5° in both the positive and negative directions. ...
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... shown in Figure 13(b), the negative rolling moment curve slope of the WBN, which represents the lateral static stability contribution of the WBN, is indeed smaller for the power-on configuration than for the power-off configuration in the tested range of sideslip angels. However, it can be found in Figure 13(a) that the lateral stability of the power-on configuration is not always smaller than that of the power-off configuration when the magnitude of the sideslip angle is greater than 5° in both the positive and negative directions. This is because the lateral static stability is closely related not only to the WBN but also to the VTP. ...
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... is because the lateral static stability is closely related not only to the WBN but also to the VTP. As shown in Figure 13(a and c), due to the significant increase in the lateral static stability contribution of the VTP between β = −5° and −15°, the magnitude of airframe rolling moment curve slope for the power-on configuration is higher than that for the power-off configuration. Conversely, the airframe rolling moment curve slope of the power-on configuration exhibits a sharp decline between β = −15° and −20°, which results from a sudden decrease in the lateral static stability contribution of the VTP. ...
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... causes of the significant variations of the aerodynamic loads acting on the VTP with the sideslip angle will be discussed in the next section. Figure 14 demonstrates the spanwise lift distributions over the wing at sideslip angles of −10 • , 0 • and 10 • for the power-off and power-on configurations, where C L,local represents the local lift coefficient, and C represents the nondimensional local wing chord length. It is seen that the lift-peaks on the port and starboard wings in the power-on configuration are significantly higher than those in the power-off configuration. ...
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... is seen that the lift-peaks on the port and starboard wings in the power-on configuration are significantly higher than those in the power-off configuration. Additionally, lateral displacement of the propeller-induced lift-peaks in line with the leeward direction in a crosswind flow is clearly visible in Figure 14(b). This was also reported by Obert (2009). ...
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... further investigate the power effects on the lateral static stability contribution of the wing, Figure 15 compares the spanwise distributions of the wing rolling moment increment from β = 10° to 0° and β = 0° to −10° between the power-off and power-on configurations. The x coordinates are made dimensionless with the propeller radius. ...
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... shown in Figure 15, not all the wing sections exhibit a drop in the C l,local when the power is activated. For instance, on the inboard side of the starboard nacelle, the values of C l,local in the power-on configuration are higher than those in the power-off configuration. ...
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... to the significant underestimations of the pressure peaks at the VTP sections and therefore the underestimations of the forces and moments acting on the VTP at positive sideslip angles, the directional static stability behavior of the reference aircraft in negative sideslip will be paid more attention in this section. Figure 16 shows the calculated yawing moment curves of the entire airframe and the airframe components versus the sideslip angle in negative sideslip for the power-off and power-on configurations. It can be seen that the airframe yawing moment of the power-on configuration versus the sideslip angle shows intense nonlinear features. ...
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... shown in Figure 16(a), the reference aircraft experiences a significant loss in directional static stability at small sideslip angles when the power is activated. However, with the increase in sideslip angle, the yawing moment curve slope of the power-on configuration reaches or even exceeds the level of the power-off configuration. ...
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... also pointed out that this was caused by a power-induced decrease in the directional static stability contribution of the VTP and the fuselage. In this study, the low directional static stability of the power-on configuration between β = 0° and −5° results from the degradation of stability contribution of the WBN, as shown in Figure 16. ...
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... Ref. [Keller & Rudnik, 2018], the recovery of the directional static stability is attributed to the increased stability contribution of both the fuselage and the VTP. As shown in Figure 16, the increase in the directional static stability of the power-on configuration between β = −5° and −10° is mainly caused by the improvement of the VTP's contribution, while the instability of the WBN is further enhanced. However, the negative contribution of the WBN on the directional static stability between β = −5° and −10° may be serious overestimated. ...
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... the negative contribution of the WBN on the directional static stability between β = −5° and −10° may be serious overestimated. At β = −10°, as the predicted pressure distributions for the VTP sections agrees well with the experimental results (see Figure 12), the significant underestimation of the total yawing moment should mainly come from the overestimation of the yawing moments acting on the WBN. ...
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... shown in Figures 13 and 16, the rolling and yawing moment curve slope of the airframe are closed related to the contribution of the VTP. To clarify the reasons for the significant variations of the moments on the VTP with the sideslip angle caused by the propeller slipstream, the local sideslip angle (β v ) are extracted at 30 points in the plane of symmetry in front of the VTP, as depicted in Figure 17. ...
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... shown in Figures 13 and 16, the rolling and yawing moment curve slope of the airframe are closed related to the contribution of the VTP. To clarify the reasons for the significant variations of the moments on the VTP with the sideslip angle caused by the propeller slipstream, the local sideslip angle (β v ) are extracted at 30 points in the plane of symmetry in front of the VTP, as depicted in Figure 17. The averaged local sideslip angle over these 30 points versus the sideslip angle of the freestream is presented in Figure 18. ...
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... clarify the reasons for the significant variations of the moments on the VTP with the sideslip angle caused by the propeller slipstream, the local sideslip angle (β v ) are extracted at 30 points in the plane of symmetry in front of the VTP, as depicted in Figure 17. The averaged local sideslip angle over these 30 points versus the sideslip angle of the freestream is presented in Figure 18. The spanwise averaged local sideslip angle varies approximately linearly with the sideslip of the freestream for both power-off and power-on configurations. ...
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... should be noted that the averaged local sideslip angles are significantly larger than the sideslip angle of the freestream, and this can be attributed to the perturbation of the VTP on its upstream flow. Figure 19 illustrates the lateral displacement of the slipstream in negative sideslip in terms of total pressure ratio iso-surface. The total pressure ratio is defined as P t / P t,∞ , where P t represents the local dynamic pressure, P t,∞ represents the dynamic pressure of the freestream. ...
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... means that these areas are submerged in the slipstream at these conditions. As shown in Figures 21 and 22, the computed pressure distributions agree very well with the wind tunnel data on the suction peak and stagnation pressure at the VTP sections of η = 31.9% and 68.6%. ...
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... 68.6%. This indicates that the lateral displacement of the slipstream in negative sideslip shown in Figure 19 is reasonable. ...
Citations
... Propellers have been extensively used in vessels sailing in inland rivers and costal environments. Numerous studies focus on the hydrodynamic performance of propellers, and research on the mechanisms of wake instability has attracted the most attention [16][17][18]. This is because vibration, noise and structure are important problems related to propeller wake evolution. ...
The present work presents numerical research on the wake flows behind a propeller operating under three advance coefficients. Large eddy simulations are adopted to obtain the viscous flow information behind the propeller. In particular, the study highlights the comparison of the evolution characteristics and the flow physics within the propeller wakes with three advance coefficients. The predicted global force and moment coefficients and phase-average statistics of streamwise velocity agree well with the available experimental data. Compared to all other flow structures in the wake, the tip vortices are found to play the most significant role according to the results. During the pairing process of adjacent tip vortices, the tip vortices diffuse circumferentially, leading to enhanced mutual-induction effects. When the advance coefficient is low, the wake becomes distorted, and the pairing process takes place in the middle region of the flow field. As a result of their unstable motion, the four tip vortices generated by the propeller cannot be distinguished individually in the far field. Instead, they break down into smaller vortices and tend to distribute themselves uniformly in the azimuthal direction. The increase in the advance coefficient delays the pairing process. This study offers valuable insights for the design and optimization of marine propellers.
