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reactive loading due to body motions and active excitation forces due to diffraction and Froude-Krylov forces.
The incident waves are assumed to be harmonic and of small amplitude when compared to the model length. Harmonic motions allow the solution to be performed in the frequency domain. Potential flow theory is used as the fluid flow is assumed to be ideal. Calculation of hydrostatic forces combined with hydrodynamic forces and body mass characteristics is used to calculate the small amplitude rigid body response about an equilibrium mean position. Hydrostatic forces are calculated by integrating the hydrostatic pressure over the submerged hull upto the water level.Rules for hydrostatic equilibrium en-compass body weight to be equal to the buoyancy force and moments about the body to be zero.
The second order wave drift forces is evaluated using either a far-field solution or a near field solution. Full QTFs are evaluated which are used to express the second order forces.
The hydrostatic stiffness matrix, hydrodynamic loading coefficients and wave forces are transferred to backing files which are made available to other AQWA programs.
The following elements were used for modelling the FPSO in AQWA-LINE