Response of B-2 aircraft to nonuniform spanwise turbulence

Abstract

Design load requirements for random gusts prescribe a one-dimensional gust field, i.e., a field that is uniform spanwise for a vertical gust. By definition, such a gust will produce purely symmetric vehicle response with corresponding symmetric stresses. The more general case of a three-dimensional gust will cause an asymmetric response. The difference in response characteristics which may result are exemplified by the fact that at the centerline of a flying wing, symmetric shear and torsion are zero, whereas, the asymmetric values are not. Solution techniques based on cross-spectral methods have been applied to the B-2 aircraft to assess the nonuniform spanwise gust response characteristics. Results are presented comparing key vehicle response parameters for uniform and nonuniform gust loading. It is concluded that the uniform gust model generally produces the higher loads and that no additional design conditions are derived from the nonuniform gust loading. Nomenclature A = normalized root-mean-square response [Hrg] = frequency response matrix [7J = diagonal editor matrix [Kr] = covariance matrix •Kx/y = modified spherical Bessel function of the third kind of order x/y L = gust scale of turbulence N0 = mean frequency of zero crossings