Custom RAO Conversion |
 
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Custom RAO Conversion |
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If the RAO data requiring conversion is non-standard, then you are required to explicitly define an RAO conversion scheme using a series of drop-down lists. The inputs, which are largely self-explanatory, are divided into four main categories, as follows:
1.The Zero Degree Heading category allows you to define the conventions used with regard to wave heading. Specifically, you specify how the zero degree incident wave heading is oriented relative to the vessel, and whether or not the specified RAO values are to be mirrored around one or more of the vessel axes.
2.The Unit Convention category allows you to associate units with the RAO data. Specifically, you may specify units for the incident wave (frequency, period or circular frequency), incident wave headings (degrees or radians), phase angles (degrees or radians) and rotational RAO amplitudes (degrees or radians).
3.The Sign Convention category allows you to define various sign conventions used in the specification of the RAO data. Specifically, you may specify whether positive phase angles represent a phase lag or a phase lead, whether positive wave headings are measured clockwise or anti-clockwise from the zero degree heading, and whether a positive wave elevation is up or down.
4.The Direction Convention category allows you to define the sign conventions regarding the responses in each degree of freedom. For example, you can specify whether a positive heave represents vessel motion upwards or downwards, and so on.
•*RAO FORMAT is used to define custom RAO conversion settings.
•*VESSEL,INTEGRATED is used to specify all information pertaining to a vessel or vessels. Specifically, the FORMAT= input is used to specify the format of the RAO data.
•*VESSEL is used to specify the initial position and undisplaced orientation of a vessel.
•*RAO is used to specify Response Amplitude Operators for a vessel. Specifically, the FORMAT= input is used to specify the format of the RAO data.
Note also that the old *VESSEL and *RAO keywords have effectively been superseded by the new *VESSEL,INTEGRATED keyword, which accepts RAO data also, thereby eliminating the need for a separate *RAO keyword – hence the ‘integrated’ nature of the new keyword.