Calculation/Simulation of the Negative pressure generated by a 3d model of flexible bellow

Hi guys,

I have a 3d cad model of a medical bellow which I am using to generate negative pressure (NP) to suck body fluids. What I am trying to do is to enhance the 3d model of the bellow so that I can increase the generated negative pressure by the bellow. I need a way to get the generated (NP) value AFTER changing the 3d model AND according to the material that I set for the part in the program. So I need a simulation program that can achieve these tasks.

Can you tell me if there is any open source program that I can use to do these tasks? Can you please refer me to related explainational videos or posts so that I can follow the instructions there step by step to achieve the tasks?