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Ansys Learning Forum › Forums › Discuss Simulation › LS Dyna › Time varying coupling pressure for SALE FSI › Reply To: Time varying coupling pressure for SALE FSI

May 30, 2024 at 3:35 pm
Ian Do
Ansys Employee

Hello Abhemanyu,

Penalty method is always noisy by definition because we first allow for the penetration in this time step. Then correct or push back in the next time step. The applied force is not based on physical law (like Newton's) but based on ad hoc engineering estimate. There are always oscillations. Hydrostatic P is most often not the first order contribution. Other dynamic events, slamming, waves, etc. likely dominate the FSI. FSI loading is a very rough estimation at best. I do not see how a small adjustment can affect other bigger and more dominant events. A test: (a) compute P_hydro=P0+rho*g*h,  (b) monitor max fluid P, (c) compare. If (a) is on the order of (b), maybe(?). Typical contact sometimes scale the force with the bulk modulus of the mats (this is very large comparing to hydrostatic range). 

IanÂ