OpenFAST
HydroDyn: Added mass up to the instantaneous free surface in still water conditions
Is your feature request related to a problem? Please describe.
HydroDyn is able to account for the added mass up to the instantaneous free surface when using wave stretching.
---------------------- STRIP THEORY OPTIONS --------------------------------------
1 WaveDisp - Method of computing Wave Kinematics {0: use undisplaced position, 1: use displaced position) } (switch)
1 AMMod - Method of computing distributed added-mass force. (0: Only and always on nodes below SWL at the undisplaced position. 1: Up to the instantaneous free surface) [overwrite to 0 when WaveMod = 0 or 6 or when WaveStMod = 0 in SeaState]
However, when considering still water conditions, it computes the added mass on nodes below the still water level at the undisplaced position. It would be good to be able to compute the added mass up to the instantaneous free surface for conditions of still water as well.
For example, if the equilibrium in heave for a floating system is -2 m, HydroDyn should account for the added mass of these 2 additional meters. In practical terms, this could have a significant impact when computing free-decay tests.
Describe the solution you'd like Added mass up to the instantaneous free surface being considered in waves as well as still water conditions.
Describe alternatives you've considered After talking to @luwang00, I'm using a workaround were small dummy waves are used so I can enable wave stretching in SeaState and consider the added mass up to the instantaneous free surface.
Leaving this here for traceability: the proposed workaround (small dummy waves) will allow to account for the added mass till the instantaneous free surface in time domain. However, to linearize the system, still water conditions must be used. Accordingly, a portion of the added mass would be still missing.