*RAO Format

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*RAO Format

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Purpose

To define custom RAO conversion settings.

Theory

Refer to Custom RAO Conversion for further information on this feature.

Keyword Format

Each RAO format definition consists of a block of four lines. This block can be repeated as often as necessary to define further RAO formats.

Line specifying the format name:

FORMAT=Format Name

Line defining the heading:

ZERO=Heading Zero, [MIRROR=Heading Mirror] 

Line stating the units used:

HEADING=Heading Units, [WAVE=Wave Units], [PHASE=Phase Units], [ROT=Rotational Degree of Freedom Units]

Line defining the positive directions:

HEADING=Positive Heading Direction [, ELEV=Positive Wave Elevation Direction] [, PHASE=Positive Phase Definition], 

[, HEAVE=Positive Heave Direction], [, SURGE=Positive Surge Direction] [, SWAY=Positive Sway Direction] 

[, YAW=Positive Yaw Direction] [, ROLL=Positive Roll Direction] [, PITCH=Positive Pitch Direction]

Format Name cannot be MCS, AQWA, WAMIT, MOSES or ORCAFLEX – these are predefined formats that use the standard MCS RAO conventions. Each format must have a distinct name. Heading Mirror can be SURGE, SWAY, BOTH or NO. Heading Units, Phase Units and Rotational Degree of Freedom Units are either DEGREES or RADIANS. Wave Units can be HZ, PERIOD or RAD/S. Positive Heading Direction must be either CW (clockwise) or ACW (anticlockwise). Positive Wave Elevation Direction and Positive Heave Direction can be either UP or DOWN. Positive Phase Definition can be LAGGING or LEADING. Positive Surge Direction must be FORWARD or AFT. Positive Sway Direction can be PORT or STARBOARD. Positive Yaw Direction, Positive Roll Direction and Positive Pitch Direction can be either RH (right-handed) or LH (left-handed).

Note: If options are not specified they default to those specified by the MCS RAO convention.

rao conversion - define

Purpose

To define RAO conversion settings.

Table Input

Input:

Description

Conversion Name:

The name of the RAO conversion.

Mirrored RAOs:

This entry allows you to specify whether or not the RAO values specified in the vessel RAO file are to be mirrored around one or more of the vessel axes. The options are No (the default), Surge, Sway or Both.

Heading Zero Value:

The angle between the negative sense of the local vessel surge axis and a wave with zero incident wave heading, measured in degrees anti-clockwise from the bow in a plan view of the vessel. This entry defaults to zero, which means that a wave incident on the bow represents a wave heading of zero degrees.

Wave Units:

This entry allows you to select whether RAOs are specified as a function of wave frequency (Frequency [Hz] or Frequency [rad/sec]) or wave period (Period [s]) in the vessel RAO file. The default is as a function of wave frequency in Hz (Frequency [Hz]).

Phase Units:

This entry allows you to select whether phase angles specified in the vessel RAO file are given in terms of Degrees (the default) or Radians. 

Heading Units:

This entry allows you to select whether the incident wave headings specified in the vessel RAO file are given in units of Degrees (the default) or Radians.

RAO Angular Units:

This entry allows you to select whether the RAO values for the rotational degrees of freedom specified in the vessel RAO file are given in units of Degrees (per unit wave elevation) or Radians (per unit wave elevation). The default is Degrees.

Response Sign:

This entry allows you to select whether phase angles specified in the vessel RAO file define a phase lag (Lagging, the default) or a phase lead (Leading) relative to the wave elevation.

Wave Elevation Sign:

This entry allows you to select the sign convention for wave elevations. You may specify whether a positive wave elevation is Up (the default) or Down. 

Wave Heading Sign:

This entry allows you to select whether positive wave headings (as specified in the vessel RAO data) are measured Clockwise or Anti-clockwise (the default) from the point of zero-degree incident wave heading in a plan view of the vessel.

Positive Heave:

This entry allows you to select the direction convention for vessel heave. You may specify whether a positive heave represents vessel motion upwards (Up, the default) or downwards (Down).

Positive Surge

This entry allows you to select the direction convention for vessel surge. You may specify whether a positive surge represents vessel motion Forward (the default) or Aft.

Positive Sway:

This entry allows you to select the direction convention for vessel sway. You may specify whether a positive sway represents vessel motion to Port (the default) or Starboard. 

Positive Yaw:

This entry allows you to select the direction convention for vessel yaw. You may specify whether positive yaw is relative to positive heave in a Right Handed (the default) or Left Handed sense.

Positive Roll:

This entry allows you to select the direction convention for vessel roll. You may specify whether positive roll is relative to positive surge in a Right Handed (the default) or Left Handed sense.

Positive Pitch:

This entry allows you to select the direction convention for vessel pitch. You may specify whether positive pitch is relative to positive sway in a Right Handed (the default) or Left Handed sense.