Efficient FFT Simulation of Digital Time Sequences

by Robert T. Hudspeth, (M.ASCE), Asst. Prof.; Dept . of Civ. Engrg., Oregon State Univ., Corvallis, Oreg.,
Leon E. Borgman, (M.ASCE), Prof.; Depts. of Geology and Statistics, Univ. of Wyoming, Laramie, Wyo.,

Serial Information: Journal of the Engineering Mechanics Division, 1979, Vol. 105, Issue 2, Pg. 223-235

Document Type: Journal Paper


A stacked inverse finite Fourier transform (FFT) algorithm is presented that will efficiently synthesize a discrete random time sequence of N values from only N/2 complex values having a desired known spectral representation. This stacked inverse FFT algorithm is compatible with the synthesis of discrete random time sequences that are used with the more desirable periodic-random type of dynamic testing systems used to compute complex-valued transfer functions by the frequency-sweep method. An application to the generation of large random surface gravity waves by a hinged wavemaker in a large-scale wave flume demonstrates excellent agreement between the desired theoretical spectral representation and the smoothed, measured spectral representation for two types of two-parameter theoretical spectra as a result of the lengthier realization made possible by the stacked FFT algorithm.

Subject Headings: Algorithms | Surface waves | Gravity waves | Dynamic tests | Wave generation | Wave spectrum | Fourier analysis | Random waves

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