# Modeling a pressurized flexible body (balloon) in simscape multibody/fluids

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Siril TD on 27 Mar 2024
Commented: XINCHI on 25 May 2024 at 11:01
Hello,
I'm trying to model a flexible cavity in simscape that needs to be pressurized later. Basically something very similar to a balloon.
I have already done the reduced order modeling of the flexible body and constrained it in my workspace.
This flexible cavity has a small opening at the bottom which I want to use to pump air inside it to make it pressurized and inflated. To do this, I realised I need to make a simple fluids system consisting of a pressure source.
Now, I am not sure how to actually connect these two domains - the 3D geometry and the fluids domain.
Frame F3 of the flexible body is at the center of the orifice in the 3D geometry, F1 connects to the origin and F2 connects to a different rigid body. Now, how do I make this connection between the two open red open wires?
Any sort of help is really appreciated.
XINCHI on 25 May 2024 at 11:01
Hi Siril,
I'm very interested in your work. However, I am not very familiar with simscape. Have you realized the simulation of inflation process of flexible object?
It would be very grateful if you could tell me how to achieve it.

Yifeng Tang on 27 Mar 2024
Hi Siril,
I feel the problem may be way more complicated than just "the two open red open wires".
To model this pressurized flexible cavity, you'll need a way to apply the force from the air pressure onto the cavity in a distributed manner, and also to apply the constraint force from the cavity on the air volume. The latter may be a bit easier, and I think you can do that with a translational converter or a single acting actuator. To go from the air pressure and air volume to the distribution of force applied on the cavity and the volume of the cavity, I can't think of an easy way to do it.
If you know how to apply a distribution of forces to the flexible body calculated from a pressure signal, I can then help you to bridge the gap between these two domains.

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