Laser velocimetry methods applied to induced drag determination on hovering rotor blades

Ramos, Juan Carlos; Favier, D.; Berton, Éric; Nsi, M.

doi:10.2514/6.1996-2415

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“…10,11 First consider the blade section an isolated airfoil; each contribution to the total drag C dt is split into two contributions: the pro le drag C dp and the induced drag Cdi , as shown in Fig. 4.…”

Section: B Pme Methods For Induced-drag Determinationmentioning

confidence: 99%

Hover Performance Prediction Using Full-Potential Method and Comparison with Experiments

Berton

Favier

Maresca

2000

Journal of Aircraft

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A computational and experimental effort to investigate the ow around rotor blades in hover is presented. The experimental analysis of the ow eld in the immediate vicinity of the blade is supported by laser velocimetry (LV) performed on the three-dimensional velocity eld around the blade section and in its near wake. A speci c LV data processing method based on the momentum equation applied around a blade section has been developed to identify the contribution of the induced-drag component to the total sectional drag coef cient. From the computational approach, some improvements to a vortex embedding full-potential method are checked by direct comparisons with test data. Comparisons are performed for overall rotor airloads (thrust and torque coef cients), local sectional coef cients (lift and drag contributions), and ow eld characteristics, includingthe tip vortex path and the spanwise circulation distribution. Nomenclature b = number of blades Cd, Cdt = drag coef cient of airfoil section Cdi = induced drag coef cient of airfoil section Cd p = pro le drag coef cient of airfoil section Cl, Clt = lift coef cient of airfoil section C Q = rotor power coef cient C Qi = rotor induced-drag coef cient C T = rotor thrust coef cient c = rotor blade chord, m dDi = elementary induced-drag force, N dF ex = external elementary forces, N dF x = horizontal elementary force, N dF z = vertical elementary force, N n = blade rotational frequency, revolutions per second P = static pressure, Pa q V = vortical velocity, m s ¡ 1 R = rotor blade radius, m Ro = root cut out, m r = radial distance from the rotation axis, m T, Q = rotor thrust and torque, N, Nm U, V , W = radial, tangential, and axial velocities, m/s u, l = upper and lower side of the blade section V = velocity vector V e = rotational tip speed, X R, m s ¡ 1 C = blade circulation along the span, m 2 s ¡ 1 h = collective pitch angle, deg h V = blade twist law, deg q , q 1= density, kg m ¡ 3 r = rotor solidity, bc/ p R w , w b = angular blade rotation, deg X = angular rotational frequency, rad s ¡ 1

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Section: B Pme Methods For Induced-drag Determinationmentioning

confidence: 99%