A question about the Stiffness Type in Coupling

- March 13, 2024 at 8:29 am
  
  Tomas Black
  Subscriber
  
  Dear all,
  I am using LS-DYNA to simulate a bottle filled with water falling onto the ground. When setting up the Coupling, I chose "Tabular" for the Stiffness Type. Therefore, I need to input Displacement vs. Coupling Pressure. Can anyone tell me what the values (The displacement vs pressure) should be like for my simulation case?
  Best,
  Tomas
- March 15, 2024 at 3:43 pm
  
  Ian Do
  Ansys Employee
  
  Hello Tomas,
  From the manual:
  "PFAC
  LT.0: PFAC must be an integer, and -PFAC is a load curve ID.
  The curve defines the coupling pressure on the y-axis as a
  function of the penetration along the x-axis. See Remark
  6. See “How to correct leakage.”
  6. PFAC < 0 for CTYPE = 4, 5, or 6. PFAC < 0 refers to a load curve. This curve
  may be constructed with the x-axis as the penetration distance (in absolute
  length unit) and the y-axis as the maximum estimated coupling pressure. This
  curve requires only 2 points. The first point is (0.0,0.0) because no FSI pressure
  applies when no penetration occurs. The x-value for the second point is 10% of
  the minimum ALE element width, and the y-value is the to be determined maximum
  observable pressure in the ALE domain. To determine this y-value, run
  the model once with PFAC = 0.1 (the default). Then, select only the ALE domain
  and plot its pressure fringes. Next, step through time to identify the maximum
  pressure in the ALE domain, selecting the pressure peaks at or near the FSI surfaces.
  This maximum pressure becomes the y-value of the second point."
  Ian Do