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Radiation forces and Excitation forces

Hello,

I’d like to confirm about radiation and excitation files.

I saw a statement like that we can model the hydrodynamics forces on the floater by using Morison equation in QBlade Forum.
Then, I’d like to confirm if this is the same for radiation forces and excitation forces?
To be specific, does it mean that if we set proper values of added mass coefficient, drag coefficient and pressure coefficient in Morison equation, we do not have to use radiation and excitation files? Could you tell me about it?

Best Regards,
Koma

I’m sorry. Also, I have one more question if we can model radiation forces and excitation forces by using Morison equation.
In QBlade, which coefficients of Morison equation should we change to consider the effects of radiation forces and excitation forces respectively?
I would appreciate it if you could let me know.

Best Regards,
Koma

Dear Koma,

as you suggested it is also possible to use only the Morison equation to model the hydrodynamic forces on a structure. In the Morison equation the ‘added mass term’ (added mass coefficient) can be interpreted as a radiation force, whereas the ‘drag term’ (drag coefficient) can be interpreted as an excitation force.

When using the Morison equation only the coefficients typically have to be ‘calibrated’ so that the hydrodynamic response of the structure aligns with experimental tests, whereas a linear potential flow approach (radiation and excitation files) requires less calibration.

BR,

David

Thanks to your answer, I understood about the setting of radiation force and excitation force thanks to your answer. Thank you.

 

A simulation of the Lillgrund windfram in QBlade, using the Dynamic Wake Meandering Model