A91. Interpolation of spectra
Spectra are interpolated by Swan during the generation of boundary conditions,
and in the output of spectra.
The interpolation procedure is not a linear interpolation bin-by-bin, but
such that the shape of the spectra is preserved as well as possible.
This tested by interpolating two Jonswap spectra with different parameters.
2 cases are considered:
It is noted that the wave height does not vary linearly; the energy varies
linearly, so the wave height varies as the square root of distance or time.
The wave period and direction also do not vary linearly; this is mainly
because Swan computes a weighted average, so the larger energy has the
largest influence on the outcome.
- a stationary with two spectra given by means of parameters at two ends of
one side of the computational grid
- two spectra are given by means of TPAR files at two ends of
a time interval on one side of the computational grid