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 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

Far-Field Induced Drag Prediction Using Vorticity Confinement Technique

2014 ◽  
Vol 51 (6) ◽  
pp. 1953-1958 ◽  
Author(s):  
Troy Snyder ◽  
Alex Povitsky
Keyword(s):  
Far Field ◽  
Induced Drag ◽  
Vorticity Confinement ◽  
Drag Prediction

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

Unsteady Hydrofoils: Theoretical and Computational Analysis

2013 ◽  
Author(s):  
Daniel T. Valentine
Keyword(s):  
Flat Plate ◽  
Computational Analysis ◽  
Vortex Sheet ◽  
Vortex Wake ◽  
Two Dimensional ◽  
Fixed Angle ◽  
Induced Drag ◽  
Wake Model ◽  
Theoretical Results ◽  
Computational Predictions

In this paper the computational problem examined is the impulsive start of a two-dimensional flat-plate hydrofoil at a fixed angle of attack. The method applied is an equally-spaced lumped-vortex panel method. The results from a lumped-vortex wake model and a shed-vortex sheet wake model are reported. Comparisons with the linear theory of Wagner (1925), the theoretical results associated with the single lumped-vortex wake model and the full wake model are presented. In addition, it is shown that the computational predictions are consistent with results reported by Katz and Plotkin (2001); they applied a distribution of vortices to model the wake. In the present paper the importance of resolving the chordwise pressure distribution in unsteady hydrofoil problems is elucidated. New predictions of both the evolution of lift and induced drag are reported for the instantaneously started flat plate. The computational predictions are compared with theorecticalpredictions also discussed in this paper.

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 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 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

Data Summary from First AIAA Computational Fluid Dynamics Drag Prediction Workshop

2003 ◽  
Vol 40 (5) ◽  
Author(s):  
David W. Levy ◽  
Tom Zickuhr ◽  
John Vassberg ◽  
Shreekant Agrawal ◽  
Richard A. Wahls ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Drag Prediction
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