= reference length of half-chord b j = breakpoint of the jth segment c 0 , c 1 , c 2 , c 3 , c 4 = coefficients of interpolation polynomial D = generalized damping matrix fV = cubic spline function of flow velocity f i = frequency corresponding to the flow velocity at the ith step g = added structural damping for k method Im = imaginary part of complex number j = sequence number of segment K = generalized stiffness matrix k = reduced frequency k j = the jth reduced frequency in which the generalized aerodynamic matrix is computed M = Mach number M = generalized mass matrix n = number of reduced frequencies for computing aerodynamic influence matrices n a = number of frequency data in a set p = Laplace variable Q s p = rational function approximation for generalized aerodynamic matrix Q 0 j , Q 1 j , Q 2 j = complex-valued coefficient matrices of the jth segment q = vector of generalized coordinates V = flow velocity V i = flow velocity at the ith step = flow density