Comparison of Inviscid Flow Methods for Lift and Drag Calculations Over Thin-Sail Geometries

2012 ◽  
Author(s):  
Robert E. Spall ◽  
Warren F. Phillips ◽  
Brian B. Pincock
Keyword(s):  
Vortex Lattice ◽  
Lift Coefficient ◽  
Computational Cost ◽  
Inviscid Flow ◽  
Induced Drag ◽  
Line Theory ◽  
Lift And Drag ◽  
Lifting Line ◽  
Lifting Line Theory ◽  
Better Than

Solutions obtained from lifting-line, vortex-lattice, and the Euler equations are presented for a series of rigid, thin wing and sail geometries. Initial calculations were performed for an untwisted, rectangular wing. For this case, lifting line theory, vortex lattice, and Euler solutions were all in reasonable agreement. However, the lifting-line theory was the only method to predict a constant ratio of induced drag coefficient to lift coefficient squared. Similar results were found for a forward-swept, tapered wing. Additional results are presented in terms of lift and drag coefficients for an isolated mainsail, and mainsail/jib combinations with sails representative of both a standard and tall rig Catalina 27. Although experimental data is lacking, overall conclusions are that the accuracy realized from lifting-line solutions is as good as or better than that obtained from vortex-lattice solutions and inviscid CFD solutions, but at a fraction of the computational cost. The linear lifting-line results compared quite well with the nonlinear lifting-line results, with the exception of the downstream mainsail when considering jib/mainsail combinations.

Revisiting the combinatorics of lifting line and 2D vortex lattice theory

2019 ◽  
Vol 123 (1265) ◽  
pp. 993-1012 ◽  
Author(s):  
M. A. Yukish
Keyword(s):  
Lattice Theory ◽  
Automated Theorem Proving ◽  
Vortex Lattice ◽  
Alternative Proof ◽  
Convergence Properties ◽  
Combinatorial Properties ◽  
Line Theory ◽  
Tools And Techniques ◽  
Lifting Line ◽  
Lifting Line Theory

ABSTRACTThis work revisits analyses of lifting line theory by A.R. Collar from 1958, bringing to bear some modern tools and techniques. The 2D vortex lattice model is also considered. Interesting combinatorial properties and simplified expressions for terms are presented, a simplified proof of model convergence shown, extension of the convergence properties to elliptical and arbitrary wing planforms is demonstrated, and approximations provided. An alternative proof of the optimality of constant downwash is presented. Modern automated theorem proving techniques are employed in confirming the combinatorial results.

Unsteady aerodynamics investigation of deploying tandem-wing with different methods

2018 ◽  
Vol 233 (10) ◽  
pp. 3714-3733 ◽  
Author(s):  
Hao Cheng ◽  
Hua Wang ◽  
Qingli Shi ◽  
Mengying Zhang
Keyword(s):  
Fore Wing ◽  
Vortex Lattice ◽  
Lift Coefficient ◽  
Unsteady Aerodynamics ◽  
Lattice Method ◽  
Vortex Lattice Method ◽  
Induced Drag ◽  
Lifting Line ◽  
Lifting Line Method ◽  
Unsteady Lift

In the rapidly deploying process of the unmanned aerial vehicle with folding wings, the aerodynamic characteristics could be largely different owing to the effects of deformation rate and the aerodynamic interference. The investigation on the unsteady aerodynamics is of great significance for the stability analysis and control design. The lifting-line method and the vortex-lattice method are improved to calculate the unsteady aerodynamics in the morphing stage. It is validated that the vortex-lattice method predicts the unsteady lift coefficient more appropriately than the lifting-line method. Different tandem wing configurations with deployable wings are simulated with different deformation rates during the morphing stage by the vortex-lattice method. As results indicated, the unsteady lift coefficient and the induced drag of the fore wing rise with the deformation rate increasing, but it is reversed for the hind wing. Additionally, the unsteady lift coefficient of the tandem wing configuration performs well with a larger stagger, a larger magnitude of the gap and a larger wingspan of the fore wing; however, the total induced drag has a larger value for the configuration that the two lifting surfaces with the same wingspans are closer to each other.

scholarly journals Analytic and computational analysis of wing twist to minimize induced drag during roll

2019 ◽  
Vol 234 (3) ◽  
pp. 788-803
Author(s):  
Douglas F Hunsaker ◽  
Zachary S Montgomery ◽  
James J Joo
Keyword(s):  
Lift Coefficient ◽  
Analytic Solutions ◽  
Rolling Moment ◽  
Morphing Aircraft ◽  
Roll Control ◽  
Induced Drag ◽  
Gradient Based ◽  
Line Theory ◽  
Rolling Rate ◽  
Lifting Line

Geometric and/or aerodynamic wing twist can be used to produce a lift distribution that results in a rolling moment. A decomposed Fourier-series solution to Prandtl’s lifting-line theory is used to develop analytic spanwise antisymmetric twist distributions for roll control that minimize induced drag on wings of arbitrary planform in pure rolling motion. Roll initiation, steady rolling rate, and the transition between the two are each considered. It is shown that if these antisymmetric twist distributions are used, the induced drag is proportional to the square of the rolling moment, and the induced drag during a steady rolling rate is equal to that on the wing at the same lift coefficient with no rolling rate or antisymmetric twist distribution. Results also show that if these antisymmetric twist distributions are used on straight, tapered wings without symmetric twist, any rolling maneuver for which the rolling rate and rolling moment have the same sign will always produce a yawing moment in the opposite direction. Computational results are also included, which were obtained using a gradient-based optimization algorithm in combination with a modern numerical lifting-line algorithm to find the optimum twist solutions. The resulting twist, induced drag, and yawing moment solutions compare favorably with the analytic solutions developed in the text. The solutions presented here can be used to inform the design of morphing aircraft.

Induced-drag reduction of wing–wings and wings–ground configurations

2004 ◽  
Vol 108 (1088) ◽  
pp. 523-530
Author(s):  
L. Marino
Keyword(s):  
Drag Reduction ◽  
Ground Effect ◽  
Formation Flight ◽  
Optimum Configuration ◽  
Induced Drag ◽  
Aerodynamic Model ◽  
Line Theory ◽  
Aerodynamic Parameters ◽  
Lifting Line ◽  
Lifting Line Theory

Abstract The problem of induced drag reduction during formation flight is revisited by means of a simple aerodynamic model based on lifting line theory. The optimum configuration for minimum induced drag is analysed both in and out of the ground effect and the influence of the main geometrical and aerodynamic parameters is considered. The results are discussed and compared with existing numerical and experimental data.

scholarly journals LIFT AND DRAG FORCE CALCULATION METHODS USING NON‐LINEAR SECTION DATA. HISTORY AND RECENT RESEARCH

Aviation ◽  
2004 ◽  
Vol 8 (2) ◽  
pp. 9-13 ◽  
Author(s):  
Egidijus Pakalnis
Keyword(s):  
Calculation Methods ◽  
Linear Section ◽  
Section Data ◽  
Non Linear ◽  
Line Theory ◽  
Data History ◽  
Lift And Drag ◽  
Force Calculation ◽  
Lifting Line ◽  
Lifting Line Theory

In this article history and development of calculation methods of wing characteristics are presented. The development process includes the beginning in 1918 by Prandtl's classical lifting line theory and leads to resent research. The most attention is paid to non‐linear section data implementation methods in the calculation of finite span wing. The research of Philips and Snyder, Barnes, and Sivells and Neely is discussed.

Optimal wing twist distribution for roll control of MAVs

2011 ◽  
Vol 115 (1172) ◽  
pp. 641-649 ◽  
Author(s):  
M. R. Ahmed ◽  
M. M. Abdelrahman ◽  
G. M. ElBayoumi ◽  
M. M. ElNomrossy
Keyword(s):  
Roll Control ◽  
Induced Drag ◽  
Load Distributions ◽  
Air Vehicle ◽  
Gradient Based ◽  
Line Theory ◽  
Symmetric Load ◽  
Lifting Line ◽  
Lifting Line Theory

Abstract The aerodynamic design optimisation of a Micro Air Vehicle (MAV) wing is performed to obtain the optimal anti-symmetric wing twist distribution for the roll control of the MAV’s wing instead of using conventional ailerons. This twist distribution should produce minimum induced drag and achieve a better roll response. The implementation of several anti-symmetric load distributions such as the half lemniscates and the Horten distributions is studied leading to an initial solution for the optimal distribution that could achieve better roll requirements. Multhopp’s method based on Prandtl’s classical lifting line theory is used for the determination of the spanwise load distribution required during the optimisation process. The optimisation process is based on the modified feasible directions gradient based optimisation algorithm implemented in the optimisation system, VisualDOC, given by Dr. Garret Vanderplaats. The proposed optimisation process is applied to the ‘BARQ’developed MAV which has successful flight in July 2009.

scholarly journals Unsteady lifting-line theory and the influence of wake vorticity on aerodynamic loads

2021 ◽  
Author(s):  
Hugh J. A. Bird ◽  
Kiran Ramesh
Keyword(s):  
Aspect Ratio ◽  
Oscillation Frequency ◽  
Cost Model ◽  
Computational Cost ◽  
Streamwise Vorticity ◽  
Aspect Ratios ◽  
Line Theory ◽  
Lifting Line ◽  
Lifting Line Theory ◽  
Low Computational Cost

AbstractFrequency-domain unsteady lifting-line theory (ULLT) provides a means by which the aerodynamics of oscillating wings may be studied at low computational cost without neglecting the interacting effects of aspect ratio and oscillation frequency. Renewed interest in the method has drawn attention to several uncertainties however. Firstly, to what extent is ULLT practically useful for rectangular wings, despite theoretical limitations? And secondly, to what extent is a complicated wake model needed in the outer solution for good accuracy? This paper aims to answer these questions by presenting a complete ULLT based on the work of Sclavounos, along with a novel ULLT that considers only the streamwise vorticity and a Prandtl-like pseudosteady ULLT. These are compared to Euler CFD for cases of rectangular wings at multiple aspect ratios and oscillation frequencies. The results of this work establish ULLT as a low computational cost model capable of accounting for interacting finite-wing and oscillation frequency effects and identify the aspect ratio and frequency regimes where the three ULLTs are most accurate. This research paves the way towards the construction of time-domain or numerical ULLTs which may be augmented to account for nonlinearities such as flow separation.

scholarly journals A Study on Aerodynamics and Stability Characteristics of a Bell-Shaped Span-Load Wing

2021 ◽  
Vol 1 (1) ◽  
Author(s):  
Nadhiratul Akmal Ab Razak ◽  
◽  
Mohd Fadhli Zulkafli ◽  
Keyword(s):  
Angle Of Attack ◽  
Aerodynamic Characteristics ◽  
Stability Characteristic ◽  
Design Team ◽  
Optimum Angle ◽  
Induced Drag ◽  
Line Theory ◽  
The Difference ◽  
Lifting Line ◽  
Lifting Line Theory

The existence of the new bell-shaped span-load wing is said to has the best lift distribution especially comparing to the elliptical wing. Bell-shaped span-load wing is designed by configuring the twist of the wing. However, the information on the aerodynamic and stability characteristics of the bell-shaped span-load wing is limited. Thus, the main purpose of the research is to evaluate the aerodynamic and stability characteristic to strengthen the claim of the capability of bell-shaped span-load wing in producing minimum induced drag. As the research is expected to be beneficial to the aviation design team, detailed information regarding the lift distribution as well as the induced drag produced is analysed at the optimum angle of attack and the results is further explained in this research. The numerical method for the analysis is done by using Lifting Line Theory (LLT) in the XFLR5 software which can analyse the wings of aircraft in terms of its aerodynamic and stability characteristic. Then, the comparison of the aerodynamic characteristics for bell-shaped span-load, elliptical span-load and tapered wing done in this research is to strengthen the appeal made stating that the bell-shaped span-load wing is the best type of wing ever existed and may replace the elliptical wing as the best wing shape with aerodynamically most efficient. The research has proven that along the wingspan, the bell-shaped span-load wing produced the lowest and minimum induced drag when being compared. At the optimum angle of attack of bell-shaped span-load wing, though the lift produced is slightly lower than the elliptical and tapered wing, the difference in the induced drag is obvious as bell-shaped span-load wing produces induced drag that is lower than 0. In other words, starting from the semi span of the wing to the wingtip, the bell-shaped span-load wing managed to be the most aerodynamically efficient wing.

Predicting Maximum Lift Coefficient for Compound Wings Using Lifting Line Theory

2021 ◽  
pp. 1-16
Author(s):  
Oliverio E. Velazquez Salazar ◽  
François Morency ◽  
Julien Weiss
Keyword(s):  
Lift Coefficient ◽  
Line Theory ◽  
Lifting Line ◽  
Lifting Line Theory
Sign in / Sign up

Export Citation Format

Share Document