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 Aerodynamic analysis of multirotor vehicles using a higher-order potential flow method

2021 ◽  
Author(s):  
Devin F. Barcelos
Keyword(s):  
Performance Prediction ◽  
Potential Flow ◽  
Higher Order ◽  
Theory Approach ◽  
Blade Element Momentum Theory ◽  
Flow Method ◽  
Momentum Theory ◽  
Radial Loading ◽  
Rotational Direction ◽  
Blade Element

A higher-order potential flow method is adapted for the aerodynamic performance prediction of small rotors used in multirotor unmanned aerial vehicles. The method uses elements of distributed vorticity which results in numerical robustness with both a prescribed and relaxed wake representation. The radial loading and wake shapes of a rotor in hover were compared to experiment to show strong agreement for three disk loadings. The advancing flight performance prediction of a single rotor was compared to a single rotor was compared to a blade element momentum theory based approach and to experiment. Comparison showed good thrust and power agreement with experiment across a range of advance ratios and angles of attack. Prediction in descending flights showed improvements in comparison to the blade element momentum theory approach. The model was extended to a quadrotorm configuration showing the differences associated to vehicle orientation and rotor rotational direction.

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

Induced drag prediction for wing-tail and canard configurations through numerical optimisation

1994 ◽  
Vol 98 (976) ◽  
pp. 199-206 ◽  
Author(s):  
G. Lombardi ◽  
A. Vicini
Keyword(s):  
Computational Procedure ◽  
Preliminary Design ◽  
Induced Drag ◽  
Drag Prediction ◽  
Aerodynamic Interference ◽  
Lifting Surfaces ◽  
Numerical Optimisation

Abstract A computational procedure has been developed in order to predict aerodynamic interference between lifting surfaces, and to devise configurations which best meet given aerodynamic requirements. The procedure, which couples an aerodynamic solver with a numerical optimisation routine, is useful in the preliminary design of aircraft. The essential features of the aerodynamic code and of the optimisation routine are described, along with the coupling criteria. Some of the most significant predictions obtained in induced-drag minimisation for wing-tail and canard configurations are described and discussed.

scholarly journals Unsteady Lift Prediction with a Higher-Order Potential Flow Method

Aerospace ◽  
2020 ◽  
Vol 7 (5) ◽  
pp. 60
Author(s):  
Julia A. Cole ◽  
Mark D. Maughmer ◽  
Goetz Bramesfeld ◽  
Michael Melville ◽  
Michael Kinzel
Keyword(s):  
Potential Flow ◽  
Vortex Lattice ◽  
Lift Coefficient ◽  
Three Dimensional ◽  
Higher Order ◽  
Two Dimensional ◽  
Flow Method ◽  
Lattice Methods ◽  
Unsteady Lift

An unsteady formulation of the Kutta–Joukowski theorem has been used with a higher-order potential flow method for the prediction of three-dimensional unsteady lift. This study describes the implementation and verification of the approach in detail sufficient for reproduction by future developers. Verification was conducted using the classical responses to a two-dimensional airfoil entering a sharp-edged gust and a sinusoidal gust with errors of less than 1% for both. The method was then compared with the three-dimensional unsteady lift response of a wing as modeled in two unsteady vortex-lattice methods. Results showed agreement in peak lift coefficient prediction to within 1% and 7%, respectively, and mean agreement within 0.25% for the full response.

scholarly journals Aerodynamic analysis of multirotor vehicles using a higher-order potential flow method

2021 ◽  
Author(s):  
Devin F. Barcelos
Keyword(s):  
Performance Prediction ◽  
Potential Flow ◽  
Higher Order ◽  
Theory Approach ◽  
Blade Element Momentum Theory ◽  
Flow Method ◽  
Momentum Theory ◽  
Radial Loading ◽  
Rotational Direction ◽  
Blade Element

A higher-order potential flow method is adapted for the aerodynamic performance prediction of small rotors used in multirotor unmanned aerial vehicles. The method uses elements of distributed vorticity which results in numerical robustness with both a prescribed and relaxed wake representation. The radial loading and wake shapes of a rotor in hover were compared to experiment to show strong agreement for three disk loadings. The advancing flight performance prediction of a single rotor was compared to a single rotor was compared to a blade element momentum theory based approach and to experiment. Comparison showed good thrust and power agreement with experiment across a range of advance ratios and angles of attack. Prediction in descending flights showed improvements in comparison to the blade element momentum theory approach. The model was extended to a quadrotorm configuration showing the differences associated to vehicle orientation and rotor rotational direction.

scholarly journals Wake-Model Effects on Induced Drag Prediction of Staggered Boxwings

Aerospace ◽  
2018 ◽  
Vol 5 (1) ◽  
pp. 14 ◽  
Author(s):  
Julian Schirra ◽  
William Bissonnette ◽  
Götz Bramesfeld
Keyword(s):  
Induced Drag ◽  
Drag Prediction ◽  
Wake Model

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

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