Calculation of Vessel Forces |
 
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Calculation of Vessel Forces |
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The following vessel forces are considered in determining the low-frequency vessel response:
(ii)Damping loads
(iii)Wave drift loads
(iv)Wind loads
(vi)Thruster loads
(vii)Mooring line loads
(viii)Riser loads
The final two of these loads (the riser and mooring line loads) are automatically applied to the vessel by virtue of the fact that these are included (coupled) with the vessel in the model. The other loads are calculated individually and are applied to the vessel CoG node.
The loads are calculated in a vessel axis system defined with its origin at the vessel centre of gravity, G, as shown in the figure below. The vessel y axis defines the local surge axis, and the z axis the local sway axis. The instantaneous vessel orientation, θ, is measured positive anticlockwise from the global Y axis. Only motions of the vessel in the horizontal plane (that is, surge, sway and yaw) are considered, so there are only three components to the vessel force vector: Fy and Fz, the forces along the local surge and sway axes respectively, and Mθ/G, the yaw moment about the vessel centre of gravity G.
