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.

Model Reduction in Flexible-Aircraft Dynamics with Large Rigid-Body Motion

Abstract: This paper investigates the model reduction, using balanced realizations, of the unsteady aerodynamics of maneuvering flexible aircraft. The aeroelastic response of the vehicle, which may be subject to large wing deformations at trimmed flight, is captured by coupling a displacement-based, flexible-body dynamics formulation with an aerodynamic model based on the unsteady vortex lattice method. Consistent linearization of the aeroelastic problem allows the projection of the structural degrees of freedom on a few vibration modes of the unconstrained vehicle, but preserves all couplings between the rigid and elastic motions and permits the vehicle fiight dynamics to have arbitrarily-large angular velocities. The high-order aerodynamic system, which defines the mapping between the small number of generalized coordinates and unsteady aerodynamic loads, is then reduced using the balanced truncation method. Numerical studies on a representative high-altitude, long-endurance aircraft show a very substantial reduction in model size, by up to three orders of magnitude, that leads to model orders (and computational cost) similar to those in conventional frequency-based methods but with higher modeling fidelity to compute maneuver loads. Closed-loop results for the Goland wing finally demonstrate the application of this approach in the synthesis of a robust flutter suppression controller.

Optimal Manoeuvres with Very Flexible Wings

Abstract: The single shooting method is used identify optimal manoeuvres in the lateral dynamics of partially-supported wings of very low stiffness. The aim is to identify actuation strategies in the design of aircraft manoeuvres in which large wing deflections can substantially modify the vehicle structural and aerodynamic features. Preliminary studies are presented for a representative high-altitude long-endurance aircraft wing in hinged configuration. Nonlinear effects due to large deflections are captured coupling a geometrically exact beam model with an unsteady vortex lattice method for the aerodynamics. The optimal control problem is solved via a gradient-based algorithm. When lowering the wing stiffness, the nonlinearities connected to the system — such as the fore-shortening effect due to large bending deflections — increase the wing lateral stability but at the same time they also reduce aileron authority. The single-shooting optimisation is shown to capture these features and to provide satisfactory results, not only when refining a predetermined actuation law but also when designing it from zero.

Influences on Safety of Flight of WIG craft

Abstract: The paper presents the motion simulation of a Wing-In-Ground (WIG) craft under the influence of wind and wave perturbations in time domain. The motion is considered in the longitudinal plane. A novel approach for generating artificial wind turbulence from prescribed kinetic energy and spectrum is proposed. Surface waves are modeled by a plane performing linear and angular oscillations. Motion simulations are carried out to show the limitations of the classical stability theory for flight safety. The calculations compare the results for the linearized and nonlinear aerodynamic characteristics of WIG crafts derived from a vortex lattice method. Furthermore the influence of the hull on the WIG aerodynamics and stability was studied using RANS simulations.

Convergence characteristics of nonlinear vortex-lattice methods for configuration aerodynamics

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.