Learning Forum

[maev5005]

I want to use AQWA to simulate a fully submerged box. However, I meet some error.

I wonder if AQWA  could simulate a fully submerged structure.

If it could, how could I run this simulation succesfully?

 

[Mike Pettit]

Hello,

Aqwa can simulate fully-submerged structures. However, in your case it looks like you may have set the structure's Generate Internal Lid option to Yes. Please try changing this to No and re-running the calculation.

Cheers, Mike

[maev5005]

Thank you. It works!!!

When I simulate a floating structure, I set the Generate Internal Lid option to YES. I still want to know when I should set the Generate Internal Lid option to YES or NO. Could you simply explain what this option means?

[Mike Pettit]

Hello, sorry for the delay, the new forum is not sending me reply notifications yet...

In some cases, the numerical method applied by Aqwa can cause unrealistic results at irregular frequencies due to motion of the fluid inside the vessel surfaces. This is a bit like the standing waves that you would expect to find between two vessels (a physical effect), except that it happens between the internal faces of one vessel (a non-physical effect). The internal lid is used to force the velocity of the free surface inside the vessel to be zero, which removes these irregular frequencies from the solution.

Generally, an internal lid is not always required, but you will not get worse results by including one. The calculation may take a bit longer, though, when you include an internal lid.

Naturally, the above only applies for vessels which cut the water surface - for submerged vessels there is no need for an internal lid.

I hope this helps!

Mike