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Vortex lattice method
About: Vortex lattice method is a research topic. Over the lifetime, 779 publications have been published within this topic receiving 9242 citations.
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TL;DR: In this article, a lifting surface method is presented that uses elements having distributed vorticity to model lifting surfaces and their shed wakes, allowing the representation of a force-free continuous wake-vortex sheet that is free of numerical singularities and is thus robust in its numerical rollup behavior.
Abstract: A lifting-surface method is presented that uses elements having distributed vorticity to model lifting surfaces and their shed wakes. Using such distributed vorticity elements allows the representation of a force-free continuous wake-vortex sheet that is free of numerical singularities and is thus robust in its numerical rollup behavior. Unlike other potential-flow methods that use discrete vortex filaments having solid-core models at their centers to avoid problems with the singularities, the numerical robustness of the new method is achieved without the subsequent solution being dependent on the choice of a cutoff distance or core size. The computed loads compare well with results of classical theory and other potential-flow methods. Its numerical robustness, computational speed, and ability to predict loads accurately make the new method ideal for the investigation of applications in which the loadings on a lifting surface depend strongly on the influence of the wake and its shape, as is the case for the two application examples presented: formation flight and rotating-wing systems.
68 citations
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TL;DR: In this paper, a numerical method for predicting the behavior of an elastic membrane wing under aerodynamic loading is presented, where the pressure distribution generated by flow over a given threedimensional surface is combined with another for finding the shape of a given membrane under a given pressure distribution.
Abstract: This paper presents a numerical method for predicting the behavior of an elastic membrane wing under aerodynamic loading. A method for finding the pressure distribution generated by flow over a given threedimensional surface is combined with another for finding the shape of a given membrane under a given pressure distribution. The pressure is calculated using a vortex lattice simulation of potential flow, and the shape is determined using a finite element representation of the membrane. An iterative scheme is employed to solve the resulting nonlinear equations which relate the shape and loading to the displacements of the surface. A simple example is given, in which the lift and stress distribution are calculated for a membrane wing with the shape and boundary constraints of an idealized hang glider. The method is equally applicable to yacht sails.
67 citations
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TL;DR: In this paper, a geometrically exact composite-beam formulation is used to model the vehicle flexible-body dynamics by means of an intuitive and easily linearizable representation based on the displacement and Cartesian rotation vectors.
Abstract: This work investigates the effect of aerodynamic interference in the coupled nonlinear aeroelasticity and flight mechanics of flexible lightweight aircraft at low speeds. For that purpose, a geometrically exact composite-beam formulation is used to model the vehicle flexible-body dynamics by means of an intuitive and easily linearizable representation based on the displacement and Cartesian rotation vectors. The aerodynamics are modeled using the unsteady vortex-lattice method, which captures the instantaneous shape of the lifting surfaces and the free inviscid wake, including large deformations and interference effects. This results in a framework for simulation of high aspect ratio planes that provides a medium-fidelity representation of flexible-aircraft dynamics with a modest computational cost. Previous independent studies on the structural-dynamics and aerodynamics modules are complemented here with the integrated simulation methodology, including vehicle trim, and linear and nonlinear time-domain solutions. A numerical investigation is next presented on a simple wing-fuselage-tail configuration, assessing the interference effects between wing wake and horizontal tail, and the downwash due to the proximity of the wake is shown to play a significant role in the longitudinal dynamics of the vehicle. Finally, a brief discussion of direct wake-tail encounters is included to show the limitations of the approach.
67 citations
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TL;DR: In this article, a configuration-invariant analytical formulation for the induced drag minimization of single-wing nonplanar systems is presented under the hypotheses of linear potential flow and rigid wake aligned with the freestream.
Abstract: Under the hypotheses of linear potential flow and rigid wake aligned with the freestream, a configuration-invariant analytical formulation for the induced drag minimization of single-wing nonplanar systems is presented. Following a variational approach, the resulting Euler–Lagrange integral equation in the unknown circulation distribution is obtained. The kernel presents a singularity of the first order, and an efficient computational method, ideal for the early conceptual phases of the design, is proposed. Munk’s theorem on the normalwash and its relation with the geometry of the wing under optimal conditions is naturally obtained with the present method. Moreover, Munk’s constant of proportionality, not provided in his original work, is demonstrated to be the ratio between the freestream velocity and the optimal aerodynamic efficiency. The augmented Munk’s minimum induced drag theorem is then formulated. Additional induced drag theorems are demonstrated following the derivations of this invariant proced...
66 citations
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TL;DR: In this paper, the aerodynamic properties of a counter-rotating wind turbine were analyzed using a vortex lattice method and validated with measurements of the NREL phase-VI rotor.
64 citations