| In this study the effect of rigid body motion on the aerodynamics of a blade in the context of computational fluid dynamics is investigated. Specifically the feathering and flapping motion of a rigid blade is studied. The three dimensional Navier-Stokes equations are solved using an implicit, time-accurate, lower-upper decomposition method. The implicit method provides higher stability time limits with the additional advantage of time accurate analysis for unsteady flow problems. The inviscid part of the equations is cast into diagonal form using the characteristics of Euler equations. Only the convection terms are treated implicitly. The explicit treatment of viscous terms offers simpler finite difference equations suitable for analytic matrix inversion than time consuming numerical matrix inversion. This method benefits from a small computational work load and small computer memory requirements and it is easily adapted for vectorization on vector machines. The computer code is used to investigate the flow over helicopter blades in hover and forward flight up to high angles of attack. The blade dynamics for a blade known as British Experimental Rotor Programme (BERP) is computed in forward flight. Results show that the blade tip acts as an effective stall barrier and improves blade performance over the conventional blades. |
