Frequency properties of the rainflow filter --
some examples in oceanography.
Abstract
The rainflow filter is a nonlinear filter
which can be used to eliminate small-amplitude oscillations in a
signal. An advantage of the rainflow filter, well known in
applications to fatigue, is that a considerable reduction of
data is made, while the calculated total damage is not
affected. An approximation of the filter in the form of a transfer
function can be obtained from spectral simulations. To validate
the so derived filter, the capability of filtering out small
cycles is examined. Further, we pay attention to calculation of
distributions for characteristic wave parameters. These methods
need as input a spectral density, where high frequencies often
are cut off. Numerical examples indicate that the rainflow
filter is advantageous to use when filtering records of sea-elevation.