Drift-Off |
 
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Drift-Off |
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The base of the riser is fixed in all 6 degrees of freedom. No other boundary conditions are required. The moored vessel centre of gravity (COG) node is also identified.
Coefficient data is used to specify low frequency wind, wave, and current loading on the moored vessel during the drift-off analysis. No “normal” or “standard” vessel data, such as vessel initial position, offset or RAO data, is specified in this run.
Offsets of -160ft, 191ft and 130° respectively are applied as constant boundary conditions at the CoG node in DOFs 2, 3 and 4 (representing the moored vessel surge, sway and yaw directions). A piecewise-linear current is also included.
The specification of boundary conditions for the dynamic analysis is the same as for the initial static run: the CoG node is released to displace further from its offset position. Drift motions are computed from the current, wind, and wave drift loading.