Learning Forum

[pc]

In Ansys Aqwa, an irregular wave has to be defined to calculate Morison force from line elements. Would anyone be able to tell how to define the irregular wave parameters i.e significant wave height and zero crossing period of this irregular wave. I am running hydrodynamic diffraction for wave period 0.5 to 5 sec

[Mike Pettit]

Hello,

Firstly you will need to turn on the 'Linearized Morison Drag' option in the Hydrodynamic Diffraction Analysis Settings. Then you can right-click on the Hydrodynamic Diffraction analysis and Insert > Irregular Wave to define the wave spectrum parameters.

I hope this helps.

Mike

[pc]

Thanks for the reply Mike
I believe the irregular wave is for the calulcation of rms velocity in the process of linearising the morison drag, if I am wrong please correct me
and does the spectrum (significant height and zero crossing period) should be defined in such a way that it covers all the wave frequencies defined in the hydrodynamic diffraction??
Thanks, PC

[Mike Pettit]

Hello,

You are correct that the wave spectrum is used to calculate the rms relative velocity, which is multiplied by a factor sqrt(8/pi) to produce a linear term for the drag calculation. The wave spectrum does not need to cover all of the wave frequencies in the Hydrodynamic Diffraction calculation.

Mike