A higher-order potential flow method for thick bodies, thin surfaces and wakes

2008 ◽  
Vol 73 (5) ◽  
pp. 706-727
Author(s):  
D. J. Bernasconi ◽  
P. M. Richelsen
Keyword(s):  
Potential Flow ◽  
Higher Order ◽  
Flow Method

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

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 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

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

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