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.

Design of the UAV aerodynamics in multiple stages

Abstract: This paper presents a methodology for aerodynamic optimization of UAV with VTOL capabilities. Aircrafts such as these usually fly at low speeds and due to that low Reynolds numbers are to be expected. The friction drag is highly dependent on the quality of the production process so unless special measures are undertaken, high friction drag coefficients could drastically influence overall performance of the aircraft. Changes of the geometrical parameters influence not only the induced drag of the wing, but also the distribution of the base drag due to sensitivity to changes of the Reynolds numbers. In order to determine the optimal geometrical parameters of the wing, a code for wing performance analysis was written. All necessary factors were calculated by utilizing the Glauert's solution of the Prandtl's equation for multi-segmented wings. By including experimental data of numerous airfoils optimized for low Reynolds numbers, the base drag distribution, along with the induced drag of the wings were calculated for a wide range of angles-of-attack. The obtained results are presented through diagrams and the methodology for the selection of the highest efficiency wing is described. The design of the T - shaped stabilizer was achieved by utilizing analytical methods while the Vortex Lattice Method, DATCOM and CFD were used for verification purposes.

Aerodynamic Analysis of a Rectangular Wing in Flapping and Twisting Motion using Unsteady VLM

Abstract: The unsteady vortex lattice method is used to model twisting and flapping motions of a rectangular flat plate wing The results for plunging and pitching motions were compared with the limited experimental results available and other numerical methods They show that the method is capable of simulating many of the features of complex flapping flight The lift, thrust and propulsive efficiency of a rectangular flat plate wing have been calculated for various twisting angles and reduced frequency with an amplitude of flapping angle(20o) And the effects of the twisting on the aerodynamic characteristics of the flapping wing are discussed by examination of their trends

Aerodynamic parameter studies and sensitivity analysis for rotor blades in axial flight

Abstract: The analytical capability is offered for aerodynamic parametric studies and sensitivity analyses of rotary wings in axial flight by using a 3-D undistorted wake model in curved lifting line theory. The governing equations are solved by both the Multhopp Interpolation technique and the Vortex Lattice method. The singularity from the bound vortices is eliminated through the Hadamard's finite part concept. Good numerical agreement between both analytical methods and finite differences methods are found. Parametric studies were made to assess the effects of several shape variables on aerodynamic loads. It is found, e.g., that a rotor blade with out-of-plane and inplane curvature can theoretically increase lift in the inboard and outboard regions respectively without introducing an additional induced drag.

Camber Effects on the Power Harvesting from Piezoaeroelastic Systems

Abstract: We investigate the effects of the aerodynamic loads on the performance of piezoaeroelastic energy harvesters. The harvester consists of a rigid airfoil having a pitch and plunge degrees of freedom with a piezoelectric coupling attached to the plunge degree of freedom. The Unsteady Vortex Lattice Method is used to model the unsteady flow and predict the loads. An iterative scheme based on Humming’s fourth order predictor-corrector method is employed to solve simultaneously and interactively the governing equations. The effects of varying the airfoil camber coeffcient are determined. We demonstrate that increasing the camber does not necessarily increase the level of the harvested power.

Reduced Order Model for Unsteady Aerodynamics of Flapping Wing Micro Air Vehicle in Hover

Abstract: Aerodynamics of a flapping wing Micro Air Vehicle (MAV) in hover is highly unsteady. Wake shed by the airfoil remains close to the airfoil surface. In this case, using low fidelity quasi-steady aerodynamic models does not give good estimate of lift and drag forces. Also, Momentum Disc Theory (MDT) alone cannot be used to model the inflow for such a complicated wake. High fidelity methods such as Computational Fluid Dynamics (CFD) are too computationally expensive for doing optimization and sensitivity studies for flapping MAVs. So, medium fidelity tools such as Unsteady Vortex Lattice Method (UVLM) have been used for modeling inflow of flapping wing mainly for forward flight conditions. However, presently there are no reduced order threedimensional (3D) aerodynamic models which can be used for doing preliminary design studies for flapping wing MAVs in hover. In the present work, a reduced order scheme is proposed which uses MDT and UVLM for modeling inflow of a flapping 2D airfoil. Results indicate that retaining only a fraction of the shed vortices is sufficient to get reasonable accuracy. For example, retaining vortices shed in the recent two out of ten oscillations reduced the error in lift by 88% as compared to quasi-steady calculation, i.e. it captures 88% of the unsteadiness. Addition of inflow calculated using MDT along with retaining two oscillations, helps capture 92% of the unsteadiness. Furthermore, the proposed scheme also helps capture about 90% of the unsteadiness in drag calculations. Since the proposed scheme simplifies computation significantly, it can be extended to create a 3D aerodynamic model for flapping wing MAV in hover.