Showing papers on "Vortex lattice method published in 1991"

An analysis method for a ducted propeller with pre-swirl stator blades

Abstract: A method is developed to analyse the flow around a ducted propeller operating in combination with a set of pre-swirl stator vanes. The method uses a boundary element method to solve for the flow around the duct and the hub and a lifting surface vortex lattice method to solve for the flow around the propeller and stators. The three-dimensional flow around the duct/hub, propeller, and stators is computed separately with the interactions between them being accounted for in an iterative manner. The interactions between the duct and the stators and between the duct and the propeller are treated in a non-axisymmetric manner. However, only the circumferentially averaged interactions between the propeller and the stators are considered. Using this method a duct and set of stators are designed to operate efficiently with an existing propeller. This model was then built and tested in the MIT water tunnel at a variety of stator pitch angles. Comparisons are made between the theoretical and experimental values for the forces on the duct, propeller and stators. A very good agreement is achieved in the region of attached flow.

Analysis of the Interaction Between Lifting Surfaces by Means of a Non-Linear Panel Method

Abstract: A non-linear vortex lattice method is used to study the interaction between lifting surfaces in incompressible potential flow. The model allows the wake of the upstream surface to roll up until convergence of the loads on the downstream surface is achieved. The use of a constraint to avoid spurious intersections between the upstream wake and the aft lifting surface is shown to lead to results in good agreement with available experimental data for canard-wing configurations, even in conditions of strong interference.

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.

Prediction of Propeller Cavitation by the Three-Dimensional Theory based on the Vortex Lattice Method

Abstract: This paper describes the numerical study on the cavitation problem of marine propellers by three-dimensional theory, based on the mathematical model of the trailing vortex geometry including the phenomena of the flow separation from the tips by using the vortex lattice method.The numerical procedure is developed to solve the partial-and super-cavitating propeller problem and to predict the cavity extent and the cavity thickness distribution.The results of the present numerical study are compared with the experimental results both in uniform and non-uniform flows. Although the comparison shows that the present method is advantageous to predict the cavity extent and the cavity thickness distribution, further problems still exist in the numerical studies to predict the propeller cavitation more accurately.