Search NASASearch

Engineering topics

Wittig, L. E.

Publications and source records attributed to Wittig, L. E..

Simulation of multicorrelated random processes using the FFT algorithm

A technique for the digital simulation of multicorrelated Gaussian random processes is described. This technique is based upon generating discrete frequency functions which correspond to the Fourier transform of the desired random processes, and then using the fast Fourier transform (FFT) algorithm to obtain the actual random processes. The main advantage of this method of simulation over other methods is computation time; it appears to be more than an order of magnitude faster than present methods of simulation. One of the main uses of multicorrelated simulated random processes is in solving nonlinear random vibration problems by numerical integration of the governing differential equations. The response of a nonlinear string to a distributed noise input is presented as an example.

Wittig, L. E.

Chladni's patterns for random vibration of a plate.

A typical Chladni pattern for pure tone excitation is shown. The aluminum plate used is clamped in a steel frame. The measured fundamental frequency is 13 Hz. The random vibration of a taut spring is discussed together with the random vibration of a thin plate and approximations for the modal sum. The Chladni pattern for wide band excitation applied at a certain point is shown together with the predicted distribution of mean square velocity as a function of the y coordinate of the plate and the experimentally measured distribution of mean square velocity as a function of y.

Crandall, S. H.