Learning Forum

[Sudhanshu]

Hi,

I am trying to calculate the forces on fender (as rounded in blue pen color ) which is attached to dolphin (smaller rectangular pieces). My dolphin is ball & socket joined through struts with main floating dock (big rectangular piece). My dolphin's dofs are fully deactivated except x & y.

Although post simulation, it seems dolphins are tossing around. Curious when I fixed the dofs of dolphins, how can it be tossing around? Can you please help me

 

[Ashish Khemka]

Hello,

 

It is possible to have such numerical problem if a structure (such as the dock in your model) has much larger mass and moments of inertia than those of the other structures linked by joints.

 

I wonder if you could define the fictitious frequency-independent added masses of heave and rotational degrees of freedom for the dolphins instead of using deactivating dofs? The added mass value of the dolphins could be in the same order of the structure mass of the dock, and the rotational added mass values could be in the same order of the moment of inertia of the dock. 

 

Regards,

Ashish Khemka