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.

Numeric computation and simulation on the hydrodynamic performance of the propeller-rudder-rudder bubble combination

Abstract: Computer simulation system of the hydrodynamic performance of the propeller-rudder-rudder bubble combination was built.The hydrodynamic performance computation method of the propeller-rudder-rudder bubble combination was studied,in which the hydrodynamic performance of the propeller was calculated with vortex lattice method,while the influence of the hub to the hydrodynamic performance of the propeller was calculated with Hess-Smith boundary element method.For thinking about the influence of the rudder and rudder bubble,the velocities induced by the rudder and rudder bubble was regarded as correction of the velocity of the incoming flow of the propeller and hub.Computer simulation system was used to design and simulate four kinds of propeller-rudder-rudder bubble combination,then the comparison with the computation result of the original propeller-rudder design was carried out.It is shown that the designed rudder bubbles can increase the efficiency of propeller obviously,in which the dissymmetric rudder bubbleachieves energy-saving effect 5.1% and increases the power reserve of main engine up to 5% in real boat test.

Broadband Noise Analysis of Horizontal Axis Wind Turbines Including Low Frequency Noise

Abstract: This paper demonstrates a computational method in predicting aerodynamic noise generated from wind turbines. Low frequency noise due to displacement of fluid and leading fluctuation, according to the blade passing motion, is modelled on monopole and dipole sources. They are predicted by Farassat 1A equation. Airfoil self noise and turbulence ingestion noise are modelled upon quadrupole sources and are predicted by semi-empirical formulas composed on the groundwork of Brooks et al. and Lowson. Aerodynamic flow in the vicinity of the blade should be obtained first, while noise source modelling need them as numerical inputs. Vortex Lattice Method(VLM) is used to compute aerodynamic conditions near blade. In the use of program X-foil [M.Drela] boundary layer characteristics are calculated to obtain airfoil self noise. Wind turbine blades are divided into spanwise unit panels, and each panel is considered as an independent source. Retarded time is considered, not only in low frequency noise but also In turbulence ingestion noise and airfoil self noise prediction. Numerical modelling is validated with measurement from NREL [AOC15/50 Turbine) and ETSU [Markham's VS45] wind turbine noise measurements.

Optimum lattice arrangement developed from a rigorous analytical basis

Abstract: The spanwise vortex-lattice arrangement is mathematically established by lattice solutions of the slender wing which are shown to be analogous to the chordwise vortex-lattice thin wing solution. Solutions for any number N of panels wing theory lift and induced drag and thin wing theory lift and moment are predicted exactly. As N approaches infinity, the slender wing elliptic spanwise loading and thin wing cotangent chordwise loading are predicted, which proves there is mathematical convergence of the vortex-lattice method to the exact answer. Based on this planform spanwise lattice arrangement, an A-vortex-lattice spanwise system is developed for an arbitrary aspect ratio A. This A-lattice has the optimum characteristic of predicting lift accurately for any value of N.

A refined 1D FE model for the application to aeroelasticity of composite wings

Abstract: The extension of a hierarchical one-dimensional structural model to aeroelasticity is the subject of the present paper. The aerodynamic model is based on the Vortex Lattice Method, VLM, whereas the refined 1D model is based on the Carrera Unified Formulation, CUF. Airfoil in-plane deformation and warping are introduced by enriching the displacement field over the cross-section of the wing. Linear to fourth-order expansions are adopted and classical beam theories (Euler-Bernoulli and Timoshenko) are obtained as particular cases. The VLM aerodynamic theory is coupled with the structural finite element model via an appropriate adaptation of the Infinite Plate Spline method. The aeroelastic tailoring is investigated for several wing configurations (by varying aspect ratio, airfoil geometry and sweep angle) and an excellent agreement with MD NASTRAN solution is provided for structural and aeroelastic cases. The effectiveness of higher-order models for an accurate evaluation of aeroelastic response of isotropic and composite wings is shown.

Pressure measurements on a thick cambered and twisted 58 deg delta wing at high subsonic speeds

Abstract: A pressure experiment at high subsonic speeds was conducted by a cambered and twisted thick delta wing at the design condition (Mach number 0.80), as well as at nearby Mach numbers (0.75 and 0.83) and over an angle-of-attack range. Effects of twin vertical tails on the wing pressure measurements were also assessed. Comparisons of detailed theoretical and experimental surface pressures and sectional characteristics for the wing alone are presented. The theoretical codes employed are FLO-57, FLO-28, PAN AIR, and the Vortex Lattice Method-Suction Analogy.