Regular Wave RAO Computation |
 
|
Regular Wave RAO Computation |
|
In the case of time domain regular wave analyses, the procedure for the computation of RAOs is as follows. Firstly a time history of the parameter of interest is generated, and the portion of the time history corresponding to the last five wave periods of the analysis (or the last whole number of wave periods if the analysis duration is less than five wave periods) is then examined and the mean of the parameter is determined.
Next, the maximum and minimum dynamic variation of the parameter from its mean value are determined for each of the five wave periods, and hence the RAO amplitude for each of the five wave periods is computed by comparison with the height of the applied regular wave. The mean and standard deviation of the five RAO amplitude values is then computed and output by the program. This approach has the advantage that the RAO amplitude is computed based on a number of regular wave periods, and the standard deviation of the RAO amplitude permits the user to determine whether the system has achieved steady-state response (and therefore, whether the computed RAO is reliable).
The computation of RAO phase angles for regular wave analyses uses a similar procedure. The mean up-crossing point of the parameter of interest is identified for each of the last five wave periods, and the RAO phase angle is computed by comparison with the mean up-crossing point of the applied regular wave for each of the five wave periods. The mean and standard deviation of the five RAO phase values are then computed and output by the program.
•*RAO is used to request the creation of RAO plots.