Learning Forum

[Wira Setiawan Syafruddin]

Hello..

Is it possible to obtain the instantaneous displacement of a structure in waves?
We can get the displacement in hydrostatics, as is well known, but I also need the change in displacement in waves over time.

Thank you

[Mike Pettit]

 

Hello,

It is possible to calculate the instantaneous displacement of a structure in waves. To do this in Aqwa Workbench, the time domain Analysis Type should be set to ‘Irregular Wave Response’ or ‘Regular Wave Response’, as this directs the Aqwa solver to calculate the hydrostatic pressure under the instantaneous wave surface. Drift loads will not be included, however.

Right-click on the time domain Hydrodynamic Response Solution, then Insert Result > Structure Forces > Hydrostatic Only. In the result details, change the Component to Global Z. Solve and evaluate this result, then divide the values by rho*g (where rho is water density and g is gravitational acceleration) to get the instantaneous volumetric displacement.

I hope this helps.

Mike

 

[Wira Setiawan Syafruddin]

Dear Mike

Excellent..Thank you very much for the the explanation. It works and helps me a lot.

How about the instantaneous restoring moment (MX)? is it possible as well?

Thank you

[Mike Pettit]

Hello,

Setting the Component of the Hydrostatic Only graph result to Global RX will give you the instantaneous hydrostatic restoring moment. You can also plot Structure Forces > Total Force/Moment, with Component set to Global RX, to see the total instantaneous roll moment for the structure.

Mike

[Wira Setiawan Syafruddin]

Dear Mike

Thank you very much for the answer. 

One more question about the parameter in the time domain: how to get the instantaneous metacentric height (GMX) of a structure?

Thank you