Learning Forum

[mdti]

Hi, I would like to use externally calculated dimensional mass matrix, mooring stiffness matrix and a frequency independent damping matrix for diffraction calculation in AQWA. The purpose of using these matrix is to calculate QTF considering the first order motions of the body. I want these matrix to be used during the first order motion computation of the body. Could you please guide me on how to input these matrices properly either in AQWA workbench or command line input file, *.DAT? If you need further information, please let me know. Best regards,    

[Shuangxing Du]

Do you mean the added mass matrix (due to hydrodynamic effect) or the structural mass matrix?

[mdti]

 

Dear Shuanxing Du,

I do mean the (6×6) structural inertia matrix. Please see a typical example https://github.com/IEAWindSystems/IEA-15-240-RWT/blob/master/OpenFAST/IEA-15-240-RWT-UMaineSemi/HydroData/wamit_inputs_2ndOrder/IEA-15-240-RWT_2nd.frc

If you need further detail, please post here.

Regards,

 

[Shuangxing Du]

In AqwaWB, you can use Point Mass to define the mass and 3x3 matrix of moment of inertia,

The mooring stiffness matrix can be defined or imported by Connection Stiffness

The frequency independent damping matrix can be defined by Additional Damping (Frequency Independent)

[mdti]

 

Thank you very much for your guidance, Shuangxing Du.

Regards,

 

 

[Shuangxing Du]

You are welcome.

[mdti]

Hi Shuangxing Du,

I was just wondering how AQWA would incorporate the marked terms in inertia matrix?

regards,

 

[Shuangxing Du]

Aqwa cannot input these terms directly. However you can input them by the frequency independent added mass matrix.