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Showing papers on "Vortex lattice method published in 1983"


Journal ArticleDOI
TL;DR: In this article, a numerical method for the calculation of the nonlinear aerodynamic characteristics of wing-body configurations in steady low subsonic flow has been developed, based on a combination of the linear source-panel method for body and the non-linear vortex-lattice method for lifting surfaces and their separated wakes.
Abstract: A numerical method for the calculation of the nonlinear aerodynamic characteristics of wing-body configurations in steady low subsonic flow has been developed. The method is based on a combination of the linear source-panel method for the body and the nonlinear vortex-lattice method for the lifting surfaces and their separated wakes. Special emphasis is given to the understanding of the behavior and the computational accuracy of the numerical method. In order to demonstrate the capabilities of the present method, total and distributed loads are computed and compared with available experimental results. The computed examples cover simple configurations as well as more complicated geometries with greater relevance to modern missiles and aircraft. Details of the calculations clarify the significant nonlinear contribution of the body to the aerodynamic properties of the configuration. Good agreement was found between the computations and the experiments.

31 citations


Journal ArticleDOI
TL;DR: In this paper, a method for calculating the longitudinal aerodynamic coefficients and the pressure distributions on a body at reasonably high angles of attack is presented, where the body is represented by a combination of source elements and vortex-lattice elements.
Abstract: A method for calculating the longitudinal aerodynamic coefficients and the pressure distributions on a body at reasonably high angles of attack is presented. The body is represented by a combination of source elements and vortex-lattice elements, including separation of the vortices at increasing angles of attack. The method is self-consistent in that the body and the separated vortex wake are treated as an integrated interacting system. The location of the separation line can be included as an arbitrary input from experimental data or can be evaluated approximately by a pressure-dependent criterion. Calculated values of the aerodynamic coefficients and pressure distributions on cone-cylinder and ogive-cylinder bodies compare well, qualitatively and quantitatively, with experimental data, including simulation of the dependence on Reynolds number.

25 citations



Journal ArticleDOI
TL;DR: In this paper, it was shown that rolling moments can be induced on the antisymmetric fins by the radial flow generated at the base of the configuration, either over the converging separated wake or over the diverging plume of a rocket motor.
Abstract: A possible reason for the induced rolling moments occurring on wraparound-fi ns (WAF) configurations in subsonic flight at zero angle of attack is suggested. The subsonic potential flow over the configuration at zero incidence is solved numerically. The body is simulated by a distribution of sources along its axis, and the fins are described by a vortex lattice method. It is shown that rolling moments can be induced on the antisymmetric fins by the radial flow generated at the base of the configuration, either over the converging separated wake or over the diverging plume of a rocket motor.

9 citations


01 Dec 1983
TL;DR: In this article, the authors investigated the feasibility of using an analytical approach and the vortex lattice method (VLM) to evaluate aerodynamic interference effects present during aerial refueling.
Abstract: : This report investigated the feasibility of using an analytical approach and the vortex lattice method (VLM) to evaluate aerodynamic interference effects present during aerial refueling. While KC-10 tanker and a B-52 receiver were studied, the method applies to any tanker receiver combination. Major assumptions include: linear potential flow; tanker receiver are represented by wing planforms; fuselage effects are small; and the rolling- up process of the tanker's wing tip vortices are not considered. The analytical approach uses a lifting line followed by a semi-infinite vortex sheet to represent the tanker. Three linear lift distributions for the tanker's wing were used and equations were derived for the induced downwash at any point in space. Points on the receiver's wing were selected to indicate the tanker's effect on the receiver's flowfield. Results of the analytical equations when compared with analytical predictions were found to overpredict the induced downwash by 25-35%. VLM was used to study the effects of: rectangular vs swept wings on induced downwash; tanker tailplane on the receiver; change of angle of attack of one aircraft due to the presence of the other; and the presence of the tanker on th receiver's pitching moment. VLM results varied from the Douglas prediction for induced downwash by only 5% and were even more accurate at lower tanker angles of attack.

8 citations


Journal ArticleDOI
TL;DR: In this article, an augmented system is constructed from Marcov parameters which are derived from an appropriate numerical computation of un-steady aerodynamics, which is expressed by using augmented system which is strictly proper and of finite dimension.
Abstract: expressed by using augmented system which is strictly proper and of finite dimension The augmented system is constructed from Marcov parameters which are derived from an appropriate numerical computation of un- steady aerodynamics A simple example is given to illustrate the approximation properties of the model The characteristics of the model are: 1) no complex parameters are necessary to determine the model, 2) system stability of the model is easily guaranteed, and 3) accuracy of the model is good in both the high- and low- frequency regions Nomenclature = coefficient matrices of the nonmemory component in unsteady aerodynamics = aerodynamic matrix in the frequency domain = reference semichord (length) = pressure difference between upper and lower surfaces of the wing, dimensionless with respect to YipV2 -- impulse response of nondimensiona l pressure difference produced by the third- order derivative of they'th mode input = generalized force, dimensionless with respect

7 citations


Proceedings ArticleDOI
01 Jan 1983
TL;DR: In this paper, a design study has been conducted to optimize trim cruise flight of high performance general aviation canard aircraft which achieve minimum drag by coupling inviscid results from a vortex panel multi-element program to a momentum integral boundary layer analysis.
Abstract: A design study has been conducted to optimize trim cruise flight of high performance general aviation canard aircraft which achieve minimum drag. In order to investigate the advantages and disadvantages of canard configured aircraft, corresponding conventional tail-aft 'baseline' aircraft were designed and used for comparison. Two-dimensional predictions were obtained by coupling inviscid results from a vortex panel multi-element program to a momentum integral boundary layer analysis. Using the results of the two-dimensional vortex panel analysis, a vortex lattice method was employed to predict the finite wing results. The analysis utilized a turbulent airfoil and a natural laminar airfoil which are two NASA state-of-the-art airfoil sections. The canard aircraft designs give quantitative results of wing and canard loadings, wing-to-canard moment arm ratios, and aspect ratio effects for trim cruise flight for a wide range of wing-to-canard area ratios. Both canard and baseline aircraft achieved a 25 to 30 percent improvement in performance over typical current technology aircraft, but high canard loading necessary for trim resulted in slightly poorer performance of the canard aircraft as compared to the baseline designs.

6 citations


01 Apr 1983
TL;DR: In this paper, a numerical study of the response of aircraft wings to atmospheric gusts and nuclear explosions when flying at subsonic speeds is presented, based upon unsteady quasi-vortex lattice method, unsteedy suction analogy and Pade approximant.
Abstract: A numerical study of the response of aircraft wings to atmospheric gusts and to nuclear explosions when flying at subsonic speeds is presented. The method is based upon unsteady quasi-vortex lattice method, unsteady suction analogy and Pade approximant. The calculated results, showing vortex lag effect, yield reasonable agreement with experimental data for incremental lift on wings in gust penetration and due to nuclear blast waves.

5 citations


Proceedings ArticleDOI
01 Jun 1983
TL;DR: In this paper, the convergence characteristics of an iterative, nonlinear vortex-lattice method are investigated, and the initial conditions for the first iteration on the computed aerodynamic coefficients and on the flow-field details are presented.
Abstract: Nonlinear panel methods have no proof for the existence and uniqueness of their solutions. The convergence characteristics of an iterative, nonlinear vortex-lattice method are, therefore, carefully investigated. The effects of several parameters, including (1) the surface-paneling method, (2) an integration method of the trajectories of the wake vortices, (3) vortex-grid refinement, and (4) the initial conditions for the first iteration on the computed aerodynamic coefficients and on the flow-field details are presented. The convergence of the iterative-solution procedure is usually rapid. The solution converges with grid refinement to a constant value, but the final value is not unique and varies with the wing surface-paneling and wake-discretization methods within some range in the vicinity of the experimental result.

5 citations



Journal ArticleDOI
TL;DR: In this paper, a vortex-lattice method for cavitating flows around a two-dimensional flat plate foil is presented. And the position of the collocation points is determined, and it is sufficient to treat unknown functions which are not integral signs as step functions.