|
Environment: Data for response calculation |
|
|
Environment: Data for response calculation |
The response calculation wave type is only used for spectral response analysis, and has the following data.
The significant wave height of the truncated white noise spectrum used for the spectral response analysis. A truncated white noise spectrum has energy spread evenly over the a specified range of frequencies.
The total energy of the spectrum is determined by $\Hs$ using the standard formula $m_0 = (\Hs/4)^2$, where $m_0$ is the zeroth spectral moment, i.e. the total spectral energy. OrcaFlex reports the value of $\Tz = (m_0/m_2)^{1/2}$. This value is not editable: it depends entirely on $\Hs$.
A discussion of the issues involved in choosing $\Hs$ is given in load cases data for spectral analysis.
The frequency range of the truncated white noise spectrum used for the spectral response analysis.
The wave components that OrcaFlex uses to represent this spectrum are carefully chosen. They are selected to match the frequencies produced by the fast Fourier transform (FFT) used to calculate the spectral response. This process is described in more detail in the spectral response analysis theory section.
It is possible for the range of FFT frequencies to fail to cover the target frequency range. OrcaFlex reports the fundamental (minimum) and Nyquist (maximum) FFT frequencies on the data form, so you can see if this is the case; you will also be warned at the start of the simulation. If this happens then the simulation will still proceed, using as much of the target range as possible.
The resulting number of wave components is also reported; again, it is possible that this number is insufficient to represent the spectral response accurately, and if this is the case OrcaFlex will report an error at the start of the simulation. The number of components is governed by the length of the response calculation simulation period and the sample interval.