Accession Number : ADA290358

Title :   High-and Low-Frequency Dynamics of Isolated Blades and Rotors with Dynamic Stall and Wake.

Descriptive Note : Final rept. 1 Jan 91-30 Sep 94,

Corporate Author : FLORIDA ATLANTIC UNIV BOCA RATON DEPT OF MECHANICAL ENGINEERING

Personal Author(s) : Gaonkar, Gopal H.

PDF Url : ADA290358

Report Date : 23 NOV 1994

Pagination or Media Count : 50

Abstract : This report investigates the effects of dynamic stall and three-dimensional wake on the trim results of control inputs and periodic responses and on the damping levels of isolated hingeless rotors. The investigation overs three items: (1) the convergence characteristics of trim and damping with respect to the number of harmonics of the wake model in the presence of dynamic stall, (2) a parametric study of trim and damping over a broad range of system parameters such as thrust level and advance ratio, and (3) a comprehensive correlation with the measured lag-regressive-mode damping. The correlation includes near-zero thrust conditions in hover and forward flight to high-thrust and highly stalled conditions in forward flight with advance ratio as high as O.55 and shaft angle as high as 200. The convergence characteristics and the parametric study are based on a three-bladed isolated rotor in propulsive trim: the cantilever blades have flap bending, lag bending and torsion degrees of freedom. In the correlation study, the root-flexure-blade assembly of the experimental rotor is modeled by an offset-hinged, rigid flap-lag model and by three elastic blade models, which differ in modeling the root flexure The experimental rotor is soft inplane and operated untrimmed. The ONERA dynamic stall models of lift drag and pitching moment and a finite-state three-dimensional wake model are used. The control inputs and periodic responses as well as the Floquet transition matrix about that response are obtained by periodic shooting with damped Newton iteration. The damping levels are generated from a full Floquet analysis that includes all the structural and aerodynamic states in trim analysis and eigenanalysis.

Descriptors :   *HELICOPTER ROTORS, *ROTOR BLADES(ROTARY WINGS), *STALLING, *WAKE, *FLEXURAL PROPERTIES, ANGLES, RATIOS, PARAMETRIC ANALYSIS, PITCH(MOTION), PREDICTIONS, MODELS, PARAMETERS, DYNAMIC RESPONSE, HARMONICS, ELASTIC PROPERTIES, DAMPING, MOMENTS, BENDING, DEGREES OF FREEDOM, CORRELATION, CONVERGENCE, FLAPS(CONTROL SURFACES), SHAFTS(MACHINE ELEMENTS), LEVEL FLIGHT, THRUST, TORSION, HOVERING, CANTILEVER BEAMS, LIFT TO DRAG RATIO, THREE DIMENSIONAL FLOW, HINGELESS.

Subject Categories : Aerodynamics

Distribution Statement : APPROVED FOR PUBLIC RELEASE