Learning Forum

[Abhemanyu Palaniswamy Chandrasekaran]

As recommended in the S-ALE tutorials, I would like to set up the Fluid-Structure interaction using the *ALE_STRUCTURED_FSI keyword, with a load curve defined for the penalty coupling pressure.

1.Is there any way to roughly estimate the coupling pressure? 

2.As recommended in the guidelines, I have tried to set the curves by defining two points, one at origin and the other with (absicca = 1/10 ALE element size, ordinate = Pmax). Does this coupling pressure refer to the total pressure at the fluid-structure interface or does it only refer to the additional pressure due to the coupling?

When we have a submerged structure with a large draft, the hydrostatic pressure in the ALE domain will contribute significantly to the total pressure. So does this Pmax on the load curve have to include the hydrostatic pressure?

3.Since leakage control is automated in the new S_ALE FSI keyword, how to identify in a simulation if the set coupling pressure (from the load curve) is adequate or if the automated leakage control is getting activated?

[ido]

Hello Abhemanyu,

[1]

HOW TO CONSTRUCT PFAC LOAD CURVE:
---------------------------------
- x-axis = penetration amount, y-axis = maximum estimated coupling pressure
- point 1: [0.0, 0.0] ==> reads "no penetration, apply no P"
- point 2: 
              x2 ~ estimated as 0.1*min_ALE_elm_width
  To estimate y2:  
-    run the model with PFAC=0.1=default ==> 
-    select only the ALE mesh/domain and plot up P contours. 
-    pick the highest P in the ALE domain  (maybe we can try to pick value near the most intense FSI region).

[2]

Total pressure at the fluid-structure interface.

Total P to prevent the fluid from penetrating through the LAG surface ==> yes -  include the hydrostatic pressure

[3]

I think that there is not a booking keeping of the relative contribution to the total FSI P applied.

The result is the P applied to push the fluid back to prevent flow through. So whether the P is coming from PFAC or

from leakage control may not be critical. The procedure outline above tends to allow for the max estimated coupling

P to be used up front.

Regards,

Ian Do

[Abhemanyu Palaniswamy Chandrasekaran]

Dear Ian,

Thank you for the explanation. 

I have one further question regarding including the hydrostatic pressures.

I have a deep draft unit (Draft=120m). Hence the variation in hydrostatic pressure is high along the depth of the lagrangian part (green represents the fluid inside the lagrangian shell). 

By setting the second poing (x2,y2) to match the highest coupling pressure, does this make the coupling at the top more stiffer than required? Is there a possibility to vary the coupling stiffness along the depth?

Thanks & Regards

Abhemanyu