Moonpool Data |
 
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Moonpool Data |
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Flexcom provides an option to specify that hydrodynamic loads on sections of riser contained within the vessel moonpool are based on the water particle velocities and accelerations within the moonpool. This facility is described in detail in Hydrodynamic Properties, and you are referred to the relevant section there for further details. In terms of vessel data, the location and extent of the vessel moonpool at solution initiation must be specified, for the purpose of applying hydrodynamic loading on structures contained within the vessel moonpool.
The vessel moonpool entrains a volume of seawater that is assumed to translate and rotate with the vessel in question. The water particle velocities and accelerations within the area enclosed by the moonpool are calculated from the vessel motions, as opposed to from the ambient wave field. The moonpool is assumed to be square in cross-section and extends from the origin of the moonpool (which would typically be at the same level as the vessel keel) to above the mean water level, as shown below in the figure below.
Definition of Moonpool Origin and Initial Yaw Orientation
The initial location of the volume enclosed by the moonpool is defined by specifying the global X, Y & Z coordinates of the moonpool origin, which is located at the centre of the square that forms the bottom face of the volume enclosed by the moonpool. The orientation of the volume enclosed by the moonpool in the global YZ-plane at solution initiation is defined by θ, which is the angle between the local moonpool y-axis and the global-Y axis (measured anticlockwise from the global-Y axis), as shown in the figure above. In most circumstances, this would be the same as the initial vessel yaw orientation. At solution initiation, the volume enclosed by the moonpool is assumed to be orientated vertically (that is, the local moonpool x-axis is aligned with the global X-axis, as shown in the figure above).
The moonpool width 
also defines the overall height of a transition region between the volume enclosed completed by the moonpool and the ambient wave field. This transition zone, and how Flexcom treats riser elements within it, is illustrated and discussed in Hydrodynamic Properties, and you should referred to the relevant section there for further details if necessary.
•*MOONPOOL is used to define the location and extent of the vessel moonpool.
•*HYDRODYNAMIC SETS is used to assign hydrodynamic coefficients to element sets. Specifically, the TYPE=MOONPOOL input is used to assign hydrodynamic coefficients to elements of the structure that may be subjected to hydrodynamic loading within a vessel moonpool.
If you would like to see an example of how these keywords are used in practice, refer to A02 - Spar Production Riser.