P. Betoney, R. Celi, J.G. Leishman

The paper describes the initial development of a free-vortex rotor wake model in state-space form, which is based on the principles of vorticity transport. The governing wake equations are formulated as partial differential equations and are converted into a system of ordinary differential equations by the method of lines. The states of the model are the time varying positions in space of collocation points on the wake filaments. Linearized models are extracted numerically using finite-difference approximations. The resulting state-space models are large and order reduction is important. Three techniques are described where the state vector is approximated by a series of shape functions. The new state-space wake is validated in five different flight conditions by comparison with an existing finite-difference wake that implements the same fluid dynamics model. Results are also presented for a coupled model including the free-vortex wake, unsteady airfoil aerodynamics, and rotor blade flapping. Open loop poles of the coupled linearized system are also shown. The agreement with the finite-difference wake geometries is uniformly excellent within about half a rotor radius but deteriorates slightly further downstream in some flight conditions, although blade inflow and lift are not affected. Substantial reductions in the number of states are shown to be possible without significant degradation of accuracy.

35th European Rotorcraft Forum 2009,

Conference Paper

englisch

21,0 x 29,7 cm, 18 Seiten

DGLR-Bericht, 2009, 2009-03, 35th European Rotorcraft Forum 2009 - Conference Proceedings; S.1-18; 2009; Deutsche Gesellschaft für Luft- und Raumfahrt - Lilienthal-Oberth e.V., Bonn

NA

in getr. Zählung;

rotors, wakes, rotorcrafts

Bestellbar

2009