scholarly journals Effects of wake shapes on high-lift system aerodynamic predictions

2021 ◽  
Author(s):  
William Bissonnette ◽  
Götz Bramesfeld
Keyword(s):  
Potential Flow ◽  
Numerical Stability ◽  
Aerodynamic Performance ◽  
Design Stage ◽  
Aerodynamic Load ◽  
High Lift ◽  
Induced Drag ◽  
Predicting Performance ◽  
Wake Model ◽  
Stability Issues

High-lift devices are commonly modelled using potential flow methods at the conceptual design stage. Often, these analyses require the use of prescribed wake shapes in order to avoid numerical stability issues. The wake type used, however, has an impact on the absolute aerodynamic load predictions, which is why, in general, these methods are used to assess performance changes due to configuration variations. Therefore, a study was completed that compared the predicted aerodynamic performance changes of such variations of high-lift configurations using different wake types. Lift and induced drag results are compared with the results that were obtained using relaxed wakes and various prescribed wake shapes. Specific attention is given to predictions of performance changes due to changes in geometry. It was found that models with wakes that are prescribed below the freestream direction yield the best results when investigating performance changes due to flap deflections and flap-span changes. The effect of flap-gap sizes is best evaluated using a fully-relaxed model. The numerically most stable approach of wakes that are prescribed leaving the trailing edge upwards seems to be least reliable in predicting performance changes. Keywords: potential flow; wake model; high-lift

scholarly journals Effects of wake shapes on high-lift system aerodynamic predictions

2021 ◽  
Author(s):  
William Bissonnette ◽  
Götz Bramesfeld
Keyword(s):  
Potential Flow ◽  
Numerical Stability ◽  
Aerodynamic Performance ◽  
Design Stage ◽  
Aerodynamic Load ◽  
High Lift ◽  
Induced Drag ◽  
Predicting Performance ◽  
Wake Model ◽  
Stability Issues

High-lift devices are commonly modelled using potential flow methods at the conceptual design stage. Often, these analyses require the use of prescribed wake shapes in order to avoid numerical stability issues. The wake type used, however, has an impact on the absolute aerodynamic load predictions, which is why, in general, these methods are used to assess performance changes due to configuration variations. Therefore, a study was completed that compared the predicted aerodynamic performance changes of such variations of high-lift configurations using different wake types. Lift and induced drag results are compared with the results that were obtained using relaxed wakes and various prescribed wake shapes. Specific attention is given to predictions of performance changes due to changes in geometry. It was found that models with wakes that are prescribed below the freestream direction yield the best results when investigating performance changes due to flap deflections and flap-span changes. The effect of flap-gap sizes is best evaluated using a fully-relaxed model. The numerically most stable approach of wakes that are prescribed leaving the trailing edge upwards seems to be least reliable in predicting performance changes. Keywords: potential flow; wake model; high-lift

scholarly journals An Analysis Tool for the Conceptual Design of High-Lift Systems

2021 ◽  
Author(s):  
William J.M. Bissonnette
Keyword(s):  
Conceptual Design ◽  
Analysis Tool ◽  
High Lift ◽  
Induced Drag ◽  
Multiple Data ◽  
Robust Model ◽  
Conceptual Design Phase ◽  
Wake Interactions ◽  
Wake Model ◽  
The Impact

An aerodynamic analysis tool for the conceptual design of high-lift devices has been developed. The method employs a higher-order potential ow method that uses elements of distributed vorticity. The subsequent numerically robust model allows for strong wake interactions, even when using a relaxed wake. The method predicts lift and induced drag values that compare well with multiple data experiments, and, when implemented in a panel code, maximum lift predictions of a high-lift system are found with an error of 6% from experimental data. This method is used to assess the impact that various wake models have on lift and induced drag predictions. This study shows that significant errors can be introduced when employing a prescribed wake model set to extreme angles. Compared to an approach using CFD, the computational expense of these models is relatively low. A single analysis requires minutes, making these models suitable for the iterative conceptual design phase

scholarly journals An Analysis Tool for the Conceptual Design of High-Lift Systems

2021 ◽  
Author(s):  
William J.M. Bissonnette
Keyword(s):  
Conceptual Design ◽  
Analysis Tool ◽  
High Lift ◽  
Induced Drag ◽  
Multiple Data ◽  
Robust Model ◽  
Conceptual Design Phase ◽  
Wake Interactions ◽  
Wake Model ◽  
The Impact

An aerodynamic analysis tool for the conceptual design of high-lift devices has been developed. The method employs a higher-order potential ow method that uses elements of distributed vorticity. The subsequent numerically robust model allows for strong wake interactions, even when using a relaxed wake. The method predicts lift and induced drag values that compare well with multiple data experiments, and, when implemented in a panel code, maximum lift predictions of a high-lift system are found with an error of 6% from experimental data. This method is used to assess the impact that various wake models have on lift and induced drag predictions. This study shows that significant errors can be introduced when employing a prescribed wake model set to extreme angles. Compared to an approach using CFD, the computational expense of these models is relatively low. A single analysis requires minutes, making these models suitable for the iterative conceptual design phase

scholarly journals Wake-model effects on induced drag prediction of staggered boxwings

2021 ◽  
Author(s):  
Julian Schirra ◽  
William Bissonnette ◽  
Götz Bramesfeld
Keyword(s):  
Potential Flow ◽  
Euler Method ◽  
Higher Order ◽  
Flow Method ◽  
Induced Drag ◽  
Wake Effects ◽  
Drag Prediction ◽  
Wake Model ◽  
Lifting Surfaces ◽  
High Degree

For staggered boxwings the predictions of induced drag that rely on common potential-flow methods can be of limited accuracy. For example, linear, freestream-fixed wake models cannot resolve effects related to wake deflection and roll-up, which can have significant affects on the induced drag projection of these systems. The present work investigates the principle impact of wake modelling on the accuracy of induced drag prediction of boxwings with stagger. The study compares induced drag predictions of a higher-order potential-flow method that uses fixed and relaxed-wake models, and of an Euler-flow method. Positive-staggered systems at positive angles of attack are found to be particularly prone to higher-order wake effects due to vertical contraction of wakes trajectories, which results in smaller effective height-to-span ratios than compared with negative stagger and thus closer interactions between trailing wakes and lifting surfaces. Therefore, when trying to predict induced drag of positive staggered boxwings, only a potential-flow method with a fully relaxed-wake model will provide the high-degree of accuracy that rivals that of an Euler method while being computationally significantly more efficient. Keywords: wake-model; boxwing; induced drag; potential-flow theory

scholarly journals Wake-model effects on induced drag prediction of staggered boxwings

2021 ◽  
Author(s):  
Julian Schirra ◽  
William Bissonnette ◽  
Götz Bramesfeld
Keyword(s):  
Potential Flow ◽  
Euler Method ◽  
Higher Order ◽  
Flow Method ◽  
Induced Drag ◽  
Wake Effects ◽  
Drag Prediction ◽  
Wake Model ◽  
Lifting Surfaces ◽  
High Degree

For staggered boxwings the predictions of induced drag that rely on common potential-flow methods can be of limited accuracy. For example, linear, freestream-fixed wake models cannot resolve effects related to wake deflection and roll-up, which can have significant affects on the induced drag projection of these systems. The present work investigates the principle impact of wake modelling on the accuracy of induced drag prediction of boxwings with stagger. The study compares induced drag predictions of a higher-order potential-flow method that uses fixed and relaxed-wake models, and of an Euler-flow method. Positive-staggered systems at positive angles of attack are found to be particularly prone to higher-order wake effects due to vertical contraction of wakes trajectories, which results in smaller effective height-to-span ratios than compared with negative stagger and thus closer interactions between trailing wakes and lifting surfaces. Therefore, when trying to predict induced drag of positive staggered boxwings, only a potential-flow method with a fully relaxed-wake model will provide the high-degree of accuracy that rivals that of an Euler method while being computationally significantly more efficient. Keywords: wake-model; boxwing; induced drag; potential-flow theory

scholarly journals Variable cant angle winglets for improvement of aircraft flight performance

Meccanica ◽  
2020 ◽  
Vol 55 (10) ◽  
pp. 1917-1947
Author(s):  
J. E. Guerrero ◽  
M. Sanguineti ◽  
K. Wittkowski
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Drag Reduction ◽  
Fuel Efficiency ◽  
Aerodynamic Performance ◽  
Flight Performance ◽  
Sweep Angle ◽  
Aircraft Flight ◽  
Induced Drag ◽  
Aircraft Performance

Abstract Traditional winglets are designed as fixed devices attached at the tips of the wings. The primary purpose of the winglets is to reduce the lift-induced drag, therefore improving aircraft performance and fuel efficiency. However, because winglets are fixed surfaces, they cannot be used to control lift-induced drag reductions or to obtain the largest lift-induced drag reductions at different flight conditions (take-off, climb, cruise, loitering, descent, approach, landing, and so on). In this work, we propose the use of variable cant angle winglets which could potentially allow aircraft to get the best all-around performance (in terms of lift-induced drag reduction), at different flight phases. By using computational fluid dynamics, we study the influence of the winglet cant angle and sweep angle on the performance of a benchmark wing at Mach numbers of 0.3 and 0.8395. The results obtained demonstrate that by adjusting the cant angle, the aerodynamic performance can be improved at different flight conditions.

scholarly journals Unsteady experimental and numerical investigation of aerodynamic performance in ultra-high-lift LPT

2020 ◽  
Vol 33 (5) ◽  
pp. 1421-1432 ◽  
Author(s):  
Xiao QU ◽  
Yanfeng ZHANG ◽  
Xingen LU ◽  
Junqiang ZHU
Keyword(s):  
Numerical Investigation ◽  
Aerodynamic Performance ◽  
High Lift
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