Showing papers on "Vortex lattice method published in 2001"

Structural Wing Sizing for Multidisciplinary Design Optimization of a Strut-Braced Wing

Abstract: A structural and aeroelastic model for wing sizing and weight calculation of a strut-braced wing is described. The wing weight is calculated using a newly developed analysis accounting for the special nature of strut-braced wings. A specially developed aeroelastic model enables one to consider wing flexibility and spanwise redistribution of the aerodynamic loads during in-flight maneuvers. The structural model uses a hexagonal wing-box featuring skin panels, stringers, and spar caps, whereas the aerodynamics part employs a linearized transonic vortex lattice method. Thus, the wing weight may be calculated from the rigid or flexible wing spanload. The calculations reveal the significant influence of the strut on the bending material weight of the wing. The strut enables one to design a wing featuring thin airfoils without weight penalty. It also influences the spanwise redistribution of the aerodynamic loads and the resulting deformations. Increased weight savings are possible by iterative resizing of the wing structure using the actual design loads. As an advantage over the cantilever wing, the twist moment caused by the strut force results in increased load alleviation, leading to further structural weight savings.

An Improved Vortex Lattice Method for Nonstationary Problems

Abstract: The vortex lattice method is improved for modeling nonlinear highly nonstationary processes appearing in an interaction of bodies that undergo an irregular motion in a proximity of solid boundaries with large-scale vortex structures. We show that keeping the condition of freezing the vortex buildups in the medium leads, in the vortex lattice method, to eliminating the arbitrariness in the calculated time step, singularity radius, and the buffer-zone radius.

Analysis of the cavitating flow around the horn-type rudder in the race of a propeller

Abstract: This paper describes numerical methods by a mixed formulation of the boundary value problem (BVP) for the prediction of the cavitating flow around the horn-type rudder working behind a propeller. The blade BVP is treated by the classical vortex lattice method, whereas the rudder BVP is solved by the surface panel method. The three-dimensional flow around the rudder and the propeller is computed simultaneously, considering the interactions between them. A modified kinematic boundary condition is applied to predict the mean velocity and flow volume through gap flow region of the horn-type rudder. To validate the numerical scheme, an experiment is performed in large cavitation tunnel. The surface pressure distributions and cavity patterns on the horn-type rudder are investigated and compared with computational results, showing good agreement with measured results.

Aerodynamic, dynamic and conceptual design of a fire-fighting aircraft

Abstract: This paper presents an evaluation of available aircraft types and demonstrates the lack of a low cost aircraft optimized for fighting forest fires, spreading viscous liquids for land reclamation and spraying pesticides over forest areas It shows that among critical areas demanding special consideration are (a) the development of mathematical models for the water bomb-aircraft separation and the aircraft transient dynamics following separation, (b) the identification of parameters influencing the coherence of the water column and effectiveness of water delivery for fire fighting, (c) choice of aircraft configuration and (d) hopper configuration Design and numerical analysis have led to the selection of the biplane as the best aircraft The main aerodynamic characteristics for the selected aircraft have been computed by means of panel methods, the so-called modified Hess method for thick wings and bodies and/or the vortex lattice method for thin lifting surfaces Different gaps and staggers and th

Wind-Power Transforming Systems

Abstract: In this article, we give a brief account of theoretical and experimental investigations, as well as engineering designs, of different types of rotors (propeller-type rotors and Darrieus-type rotors). In numerical studies, we used the vortex lattice method. We obtained instant and averaged-in-time values of the coefficients of the centrifugal, drag, side, and head forces, as well as the value of the relative torque, the wind-power use coefficient, the configuration of the vortex trace, and the velocity field and contour lines. The results of numerical studies agree well with experimental data.

System Identification and Pod Method Applied to Unsteady Aerodynamics

Abstract: The representation of unsteady aerodynamic flow fields in terms of global aerodynamic modes has proven to be a useful method for reducing the size of the aerodynamic model over those representations that use local variables at discrete grid points in the flow field. Eigenmodes and Proper Orthogonal Decomposition (POD) modes have been used for this purpose with good effect. This suggests that system identification models may also be used to represent the aerodynamic flow field. Implicit in the use of a systems identification technique is the notion that a relative small state space model can be useful in describing a dynamical system. The POD model is first used to show that indeed a reduced order model can be obtained from a much larger numerical aerodynamical model (the vortex lattice method is used for illustrative purposes) and the results from the POD and the system identification methods are then compared. For the example considered, the two methods are shown to give comparable results in terms of accuracy and reduced model size. The advantages and limitations of each approach are briefly discussed. Both appear promising and complementary in their characteristics.