Simulation of dual porosity in coal using COMSOL Multiphysic

[Nima7871]

Hi,

I would kindly appreciate it if someone could help me with my simulation problem. I am trying to simulate dual porosity in coal and the interaction of coal matrix and fracture flow. The problem I'm having is I can't assign separate domains with different pressures for matrix and fracture in coal (I don't know how to define boundary conditions for matrix and fractures for different domains). In other words, I do not know how to couple fracture and matrix flow in COMSOL settings.

Regards,
Nima

 

[Hyo X]

and
https://en.wikipedia.org/wiki/Dirichlet_boundary_condition and https://en.wikipedia.org/wiki/Neumann_boundary_condition
what kind of boundary do you have?
we don't know what fracture and matrix flow mean.

 

[Nima7871]

Hi Hyo,

Thanks very much for your reply. I need to couple two phenomena namely diffusion in coal matrix and Darcy flow in fracture. These are technical terms for geotechnical problems. The gas in coal is stored in matrix which is then diffused into coal fracture due to pressure gradient and then is driven through the cleats (Fractures) around coal matrix through Darcy flow. I need to define two separate domains in my model with two different pressures, representing coal matrix and fractures. I do not know how to define my geometry and not too sure if I can use fracture flow module under porous media and subsurface flow module in COMSOL. I might be able to define boundary conditions once I can create appropriate geometry and use the right flow module. I think I first need to come up with the right geometry which I'm not clear about.

Regards,
Nima

 

[Sikandar Khan]

Hi Nema

I think comsol didn't solve for dual porosity directly because the poroelasticity module is only for single porosity modeling. Also if you can check the fracture flow module can not simulate and assign the fractures in a 3 D model. Fracture flow can only be applied at the boundaries. Did you tried it (means did you have coupled the matrix and fracture flow?). I am working on the same topic and facing the same problem.

Sikandar