Learning Forum

[Thamanna Iqbal]

In LS DYNA, the motion of a plate with an initial velocity in downward direction in an air domain is modelled for FSI using ALE mesh. When checking the results the velocity of plate is getting reduced so quick which is not the expected result. What could be the reason for this? What are the required keywords?

[Ian Do]

ALE is a hydrocode, meaning it is designed for high gradients problems mostly. Sometimes it can be used with lower P problems, but plate to air or aerodynamics effects is not its intended use. If you have not used ALE in LS-DYNA before you should at least attend the Comprehensive ALE seminar first before first use. 

If the plate slows down a lot then your mat data (too light or too heavy mat?) or BC's/IC's may be incorrect. The required KWs are the set that define the ALE mats and their interactions with the LAG structures.  The coupling KW is ALE_STRUCTURED_FSI (for S-ALE solver, recommended) or CONSTRAINED_LAGRANGE_IN_SOLID (for older ALE solver).

Pls watch the seminar on ALH before trying to model ALE FSI. 

[Thamanna Iqbal]

I have used *CONSTRAINED_LAGRANGE_IN_SOLID for coupling. Once the simulation is completed, the plate is moving down but the decrease of velocity is in a very quick time, maybe because of high drag force. Is there any way to correct this issue?

[Ian Do]

Hello Thamana,

As mentioned, pls check:

• check mat data (too light or too heavy mat?)
• check BC's/IC's

BUT - ALE is not the right tool for aerodynamic drag modeling. For subsonic, ICFD is better.

Ian Do