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.

Prediction of propeller blade pressure distribution with a panel method

Abstract: : Panel methods and their underlying theory are reviewed with regard to hydrodynamic analysis of propeller performance. Green's identity is used to convert the differential Laplace's equation into an integral equation. The velocity potential on the surface of the lifting body can be expressed by integrating the potential induced by source/doublet singularities distributed over the surface. The numerical discretizations of the boundary surface, singularity distributions, the integral equation, and the formulation of the panel method are discussed. The advantages of the application of panel methods in viscous/inviscid interactive procedures and propeller blade design are outlined. Results of propeller blade analysis with the panel method are presented, comparing the prediction of the VSAERO panel method and a vortex lattice method with experimental data. The panel method, which includes consideration of propeller hub effects, gives predictions in good agreement with experimental data. Keywords: Marine propellers hydrodynamic characteristics.

A vortex-lattice method for calculating longitudinal dynamic stability derivatives of oscillating delta wings

Abstract: A nonsteady vortex-lattice method is introduced for predicting the dynamic stability derivatives of a delta wing undergoing an oscillatory motion. The analysis is applied to several types of small oscillations in pitch. The angle of attack varied between + or - 1 deg, with the mean held at 0 deg when the flow was assumed to be attached and between + or - 1 deg and the mean held at 15 deg when both leading-edge separation and wake roll-up were included. The computed results for damping in pitch are compared with several other methods and with experiments, and are found to be consistent and in good agreement.

Piezoelectric energy harvesting from an oscillating wing

Abstract: We investigate power levels that can be harvested from aeroelastic vibrations of an elastically-mounted wing that is supported by nonlinear springs. The energy is harvested by attaching a piezoelectric transducer to the plunge degree of freedom. A model that tightly couples the electromechanical model with the three dimensional unsteady vortex lattice method for the prediction of the unsteady aerodynamic loads is developed. The effects of the electrical load resistance, nonlinear torsional spring and eccentricity between the elastic axis and the gravity axis on the level of the harvested power are determined for a range of operating wind speeds. The results show that there is an optimum value of load resistance that maximizes the level of harvested power. The results also show that the nonlinear torsional spring plays an important role in enhancing the level of the harvested power. Furthermore, the harvested power can be increased by properly choosing the eccentricity. This analysis helps in the design of piezoaeroelastic energy harvesters that can operate optimally at prevailing air speeds.

Model Order Reduction of Aerodynamics for Flight Dynamic Simulations

Abstract: In the context of model order reduction and data compression, a parametric implementation of the proper orthogonal decomposition is presented. A linear vortex lattice method is adapted for unmodelled effects, creating large amounts of variables per parametric space and the basis formed via the method of snapshots. Based on the distribution of the sytems "energy" over the decomposition's modes, only a few can be retained resulting in a reduced order model. The behaviour of the general coefficients in the parametric space is examined and a cubic spline curve fitting procedure implemented. Due to the low number of interpolated modes, real time capabilities emerge. The reduced model is then combined with the 6 degree of freedom nonlinear equations of motion to simulate disturbance responses and examine the stability modes. Results were validated against a reference aerodynamic data set and showed a good agreement for both, aircraft totals in the extended flight envelope and state variable time responses. The effect of reducing the retained POD modes further was investigated and the resulting differences highlighted. The decrease in accuaracy variations with increasing modes, underlined the uneven "energy" distribution. The stability modes of the linearized system for both aerodynamic models correlated well with some larger differences for the spiral mode. Computational power and memory storage issues were addressed and a number of solutions and strategies proposed.

Calculation of the hydrodynamic forces acting on a hydrofoil

Abstract: Characteristics of a hydrofoil have been treated using the lifting surface theory or the vortex lattice method and the wavemaking resistance theory, which need very complicated calculations. But these methods can not directly predict the pressure distribution on the hydrofoil with thickness. This paper presents a method to calculate the flow around the hydrofoil and the hydrodynamic forces acting on the hydrofoil using the thick wing theory and the Rankine source method. Thick wing is represented by the source distribution on the hydrofoil and the vortex distribution on the chord. The strength of these singularities are obtained from the boundary condition on the hydrofoil and the Kutta's condition. In order to represent the wave flow, the source distribution is set on the still water surface so as to satisfy the Dawson's double-model linearised free surface condition. Since the flow field is calculated using these singularities, the pressure distribution, the lift and drag on the hydrofoil are obtained easily. As the numerical examples, we show the wave profiles or the wave contours, the pressure distributions and comparison of the lift and drag coefficients of the 2-D hydrofoils (NACA 0009 and NACA 0012) and the 3-D hydrofoils (NACA 64, A 412, Aspect Ratios of 4 and 10) between calculated and experimental results.