The Influence of Rainflow Filtering on the Distributions of Characteristic
Wave Parameters
Jesper Rydén
Centre for Mathematical Sciences
Mathematical Statistics
Lund Institute of Technology,
Lund University,
2000
ISSN 14039338

Abstract:

Calculation of the exact distributions for characteristic wave parameters
by means of the regressionapproximation method requires as input a spectral
density. The highfrequency cutoff in the spectrum plays an important role
for such computations. We use the rainflow filter as an alternative to the
bandpass filters traditionally used. The rainflow filter is a nonlinear
filter which can be used to eliminate smallamplitude oscillations in a signal.
For a spectrum of JONSWAP type, the joint distribution of crest height and
crest period is calculated, and the filtering approaches are compared. The
rainflow filter yields results which are closer to the distributions obtained

from a spectrum with highfrequency content.


Key words:

wavelength, wave period, rainflow cycle, filtering, spectrum