Simulation of poroelastic material with COMSOL Multiphysics

[Stem89]

Good morning,
I was wondering if you could help me solve a problem with a poroelastic model with COMSOL Multiphysics.
It is a very simple model preliminary to my real study to understand the role of Poisson's ratio on the simulation, keeping all other parameters constant.
The model is a two-dimensional poroelastic model constituted by a circle with a circular cavity inside subjected to a radial pressure .
Being the model poroelastic, I expect that the internal pressure generates a movement of fluid and in particular I expect the material area not increase but actually with coefficients poisson low there is an increase in surface. I can not understand the physical sense of this increase in surface area. What generates the increase in surface area?

 

[_coyote_]

The increase in surface area is due to the compressibility of the material. When a pressure is applied to the material, the material compresses, reducing its volume and increasing its surface area. As Poisson's ratio decreases, the material becomes more compressible, resulting in a larger increase in surface area when a pressure is applied. This can be observed in a wide variety of poroelastic materials, such as rubber, foam, and soil.