DrAmine
Ansys Employee

To summarize you want to model the hull of the balloon becoming bigger as the pressure is reduced>Density is reduced>Mass is constant and that is why the volume of the balloon need to expand? 


 


One possible way is modelling the hull of the balloon and using UDF to move the nodes to depict the volume change (DEFINE_GRID_MOTION). I am also thinking on using Mechanical and Autodyn here.