The objective of this work is to reshape a nacelle to achieve a specified nacelle pressure distribution. The nacelle may be either isolated or installed on an airplane. There are no restrictions on the attitude (toe, incidence, and roll) and position of the nacelle. The design algorithm is coupled to two different multi-block 3-D Navier Stokes flow solvers. The coupling between design and analysis is automated to the point where the design proceeds with minimal user input. Nomenclature C -Local nacelle or wing chord. CDISC -Constrained DISC. Cp -Coefficient of pressure. DISC -Direct Iteration Surface Curvature. O(..) -Order of magnitude. R -Local nacelle radius. X -Streamwise coordinate. theta -Angle running from the nacelle crown through the keel (outboard side) and back up to the crown (inboard side).
A numerical method is presented for calculating the unsteady transonic rotor flow with aeroelasticity effects. The blade structural dynamic equations based on beam theory were formulated by the finite element method and were solved in the time domain instead of the frequency domain. A global-local coordinate-transformation matrix was used to reduce the inaccuracy caused by large blade deformations. A new structure code was developed and was validated by comparing the computed natural frequencies with experimental data of a model rotor blade. For different combinations of precone, droop, and pitch, the correlations are very good in the first three flapping modes and the first twisting mode. However, the predicted frequencies are too high for the first lagging mode at high rotational speeds. This new structure code has been coupled into a transonic rotor flow code, TFAR2, to demonstrate the capability of treating elastic blades in transonic rotor flow calculations. The flowfields for a model-scale rotor in both hover and forward flight are calculated. Results show that the blade elasticity significantly affects the flow characteristics in forward flight. Nomenclature A = blade cross-section area a = local speed of sound a^ -far-field speed of sound a o-<*5 = coefficients in Newmark method fl 0 ,«i = constants for Rayleigh damping [C] = element damping matrix [C] = damping matrix for the blade c = blade chord length E = Young's modulus G = shear modulus [G]= rotational matrix for entire blade I y j z = blade cross-section moments of inertia about y and z axes, respectively / = torsional rigidity K = stiffness matrix for the blade K E = nonrotating element stiffness matrix K G = element geometric stiffness matrix K GT = element geometric-stiffness-like matrix / = blade element length [M] = element mass matrix [M] = mass matrix for the blade n = unit vector normal to the blade surface P(t) = aerodynamic load vector q = flow velocity g, = generalized coordinates
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