ido
Ansys Employee

Hello Caleb,

[Q1] How to remove the water from where the piles are supposed to be and set it to a void material

[A1] If your piles are solid LAG parts, you can define a segment-set representing the pile’s surface. Make sure all the segment normals point in the same dir. Then you can use that segment-set as a “container” for doing vol-filling to fill in that space. 

Is there any reason you are not using ICFD for this? It is implicit and can deal with longer run time. You need “My simulation runs for 15 seconds so each pile should be subjected to 7-8 waves. “

ALE is an explicit hydrcode. So its

dt_max ~ [min_elm_width/sound_speed] 

It depends on how thick your piles are and how many ALE elms you have spanning that thickness. To do proper penalty coupling you can try to account for the overlapped space under the piles as questioned in [Q1] by doing the vol-filling as discussed. 

If the ALE elms are big and there are not too may ALE elms across the piles’ thickness, then you may try by simple treat the piles as being submerged in the water space (even in the overlapped space). We’ll get some interaction forces, but we cannot be sure how well the piles-water coupling may be. You can try to validate this by simple/small examples of submerged FSI and compare to data.

In any case, 15s is an eternity for hydrocodes! Of course it depends on how many elms you have, which determines the elm width, which determines the dt ==> how long to run 15s! etc.

Given the fact that LAG:ALE relative mesh resolution should be as close to 1:1 as possible as a guideline, 

Regards,

Ian Do