Modelling the aeroelastic response and flight dynamics of a hingeless rotor helicopter including the effects of rotor-fuselage aerodynamic interaction

Abstract

This paper presents a mathematical approach for the simulation of rotor-fuselage aerodynamic interaction in helicopter aeroelasticity and flight dynamics applications. A Lagrangian method is utilised for the numerical analysis of rotating blades with nonuniform structural properties. A matrix/vector-based formulation is developed for the treatment of elastic blade kinematics in the time-domain. The combined method is coupled with a finite-state induced flow model, an unsteady blade element aerodynamics model, and a dynamic wake distortion model. A three-dimensional, steady-state, potential flow, source-panel method is employed for the prediction of induced flow perturbations in the vicinity of the fuselage due to its presence in the free-stream and within the rotor wake. The combined rotor-fuselage model is implemented in a nonlinear flight dynamics simulation code. The integrated approach is deployed to investigate the effects of rotor-fuselage aerodynamic interaction on trim performance, stability and control derivatives, oscillatory structural blade loads, and nonlinear control response for a hingeless rotor helicopter modelled after the Eurocopter Bo105. Good agreement is shown between flow-field predictions and experimental measurements for a scaled-down isolated fuselage model. The proposed numerical approach is shown to be suitable for real-time flight dynamics applications with simultaneous prediction of structural blade loads, including the effects of rotor-fuselage aerodynamic interaction. NOMENCLATURE B jinfluence coefficient of the jth source panel element on the evaluation point with co-ordinates (x, y, z) m C, D wake curvature influence matrix (Krothapalli and Zhao models, respectively) g gravitational constant, m/sec 2 I xx , I yy , I zz , I xz Fuselage roll, pitch, yaw, and roll-yaw moments of inertia, kg . m 2 K Re wake curvature parameter L c , L s Cosine and sine inflow gain matrices M c , M s Cosine and sine apparent mass matrices n unit vector perpendicular to dS of S b positive towards the direction of the potential jump, m N b , N p number of blades and quadrilateral panel elements p, q, r angular velocity components of the fuselage expressed about the fuselage reference axes frame, rad/sec P rotor main rotor power required, kW P _ n m (ν) normalised associated Legendre function of first kind P(x, y, z) induced potential evaluation point with Cartesian co-ordinates (x, y, z) q _ , p _ normalised pitch and roll rates = , r geometric distance of source panel from evaluation point P(x, y, z), m r, R local and total rotor blade radius, m r _ non-dimensional radial co-ordinate on the rotor disk = S state of wake spacing, = 2πV T S b three-dimensional body surface, m 2 t time, sec t _ non-dimensional time = Ωt V, V T flow parameter and total flow at the rotor disk plane, dimensionless V flight helicopter flight speed, m/sec u _ , v _ , w _ normalised fuselage induced velocity perturbations v induced velocity perturbation vector = [u v w] T , ms -1 V c , V s Cosine and sine mass flow parameter mat...

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Numerical Study of Fuselage Impact on Acoustic Characteristics of a Helicopter Rotor

“…A growing number of publications [1][2][3][4][5] focusing on the influence of fuselage on the helicopter rotor aerodynamcis demonstrate the importance of the subject. Recently, due to increasingly stringent International Civil Aviation Organization (ICAO) requirements on the permissible noise levels produced by aircrafts, including helicopters, the focus of research has shifted from rotor aerodynamics to the acoustics generated by the rotor in the presence of fuselage [6][7][8][9]. The simulation of the acoustics of the entire helicopter including the fuselage presents a challenge as it requires substantial computational resources and efficient parallel algorithms.…”