Learning Forum

[S.S.S.ShankaVasuki]

Hi,

I am trying to simulate connected bodies in ansys aqwa. But I am getting certain errors associated with the mesh and the connection between the bodies as shown in the figures.

Mass = 62kg

Draft = 0.018m

Thickness = 0.08m

length = 1.88m

So my questions are:

1. How do I set the right mesh settings. I did read the ansys theory manual about mesh quality check, but I am not sure on how to implement it in the workbench. Hence could you provide the steps in detail?
2. How do I solve the warning of closed loop of the connectors? Because, I need the hinge connectors to be the way it is in the simulation currently. Could you please let me know on to resolve this issue?

Thanks!

 

[S.S.S.ShankaVasuki]

Hi can someone help me out with this?

Now, I remeshed the geometry with triangular elements to get a total number of panels as 20363 and out of this 0.04% of the elements seem to fail hence, I also enabled the ignore modelling rules and the diffraction analysis runs without any errors. But I get a lot of errors in the hydrodynamic response analysis

I have currently reduced the number of connected bodies to three bodies to simplify the problem. But I still get a lot of errors as shown in the figure below.

I am not quite sure on why these errors pop up. Is it because aqwa cannot simulate floating structures with a small draft? or am I missing something here?

Do I have scale up the model?

So can you please help me with resolving these errors?

Thanks!

[Shuangxing Du]

(1) If possible, please use quadrilaternal panels. Please check if setting "Ignore Modeling Rule Violation" as "Yes" works. 

(2) Aqwa deals with the rigid body hydrodynamic response analysis, the close-looped redudant contraints will cause the statical indeternimated solution. The hilghlighted each pair of hinge joints could be replaced by one joint, the six longitudinal hing joints could be reduced to a single hinge at the left hand side and a ball&socket joint at the right hand side.  

(3) Please set "Generate Internal Lid" as "Yes". If the draft of the structure is less than the mesh size, Aqwa may not give accurate results.

[S.S.S.ShankaVasuki]

Hi Shuangxing,

I tried the things you mentioned for a same problem but with three connected bodies to simplify the problem and here is what I observed:

1. I tried to give all quadrilateral mesh elements with a mesh size = draft of the strucutre but this results in the total elements being greater than 40,000 which cannot be possible in aqwa. Hence I increased the mesh size to 0.025m and got total elements to be less than 40,000. Also, there are no failing elements. But my question does aqwa give unrealistic results when the draft is smaller than the mesh size or are the results still reliable?
2. I also turned the "ignore modelling rules" to yes and set "generate interal lid" as yes for all the bodies and I am getting this error.

 

Can you please let me know on how solve this error?

Thanks!!

[S.S.S.ShankaVasuki]

Hi,

Any idea on how to solve the above problem?

 

Also would scaling up the model using Froude's similitude be an option? Please let  me know

[S.S.S.ShankaVasuki]

Hi, 

could anyone help with this?