A novel Karhunen–Lo eve (KL) least-squares model for the supersonic flow of an inviscid, calorically perfect ideal gas about an axisymmetric blunt body employing shock-fitting is developed; the KL least-squares model is used to accurately select an optimal configuration which minimizes drag. Accuracy and efficiency of the KL method is compared to a pseudospectral method employing global Lagrang...

The ε-pseudospectral abscissa and radius of an n × n matrix are respectively the maximal real part and the maximal modulus of points in its ε-pseudospectrum, defined using the spectral norm. Existing techniques compute these quantities accurately but the cost is multiple singular value decompositions and eigenvalue decompositions of order n, making them impractical when n is large. We present n...

entropy flux F is related to U and to the flux f by F 9 5 U 9f 9. The (weak) solution of (1.1)–(1.4) is then unique. We use the Legendre spectral viscosity method to solve nonlinear conservation laws. This method essentially consists in adding a In this paper, we are interested in computing the entropic spectral viscosity to the equations for the high wavenumbers of solution of Eq. (1.1), i.e.,...

Polynomial approximations of computationally intensive models are central to uncertainty quantification. This paper describes an adaptive method for nonintrusive pseudospectral approximation, based on Smolyak’s algorithm with generalized sparse grids. We rigorously analyze and extend the nonadaptive method proposed in [P. G. Constantine, M. S. Eldred, and E. T. Phipps, Comput. Methods Appl. Mec...

In [BMV03]and [Bre02] the authors proposed to compute the characteristic roots of Delay Differential Equations (DDEs) with multiple discrete and distributed delays by approximating the derivative in the infinitesimal generator of the solution operator semigroup by Runge-Kutta (RK) and Linear Multistep (LMS) methods, respectively. In this work the same approach is proposed in a new version based...

The problem of performance optimization of a maneuvering re-entry vehicle is studied. The objective is to determine an optimal steering law for a high lift-to-drag ratio vehicle. An optimization criteria is derived that attempts to maximize the control margin of the vehicle in order to account for unmodeled perturbations during actual flight. The optimization problem is formulated as an optimal...

Decoupled fractional Laplacian wave equation can describe the seismic wave propagation in attenuating media. Fourier pseudospectral implementations, which solve the equation in spatial frequency domain, are the only existing methods for solving the equation. For the earth media with curved boundaries, the pseudospectral methods could be less attractive to handle the irregular computational doma...

An initial value problem with piecewise constant coe cients is considered. The accuracies for both nite di erence methods and the pseudospectral method are analyzed, and a modi cation of the initial value problem is suggested. The modi ed problem is shown to have the same temporal period as the original problem does, and a second order accuracy is obtained for the pseudospectral method at integ...

In this paper, we investigate the mixed Laguerre-Legendre interpolation approximation and its application. Some approximation results are established. A mixed Laguerre-Legendre pseudospectral scheme is constructed for incompressible fluid flow in an infinite strip. Its stability and convergence are proved. Numerical results show the efficiency of this new approach.