Hi Tianran,
thank you for your mail and your interest in Dumux.
> I understand that
> assigning the same saturation for both the porous media and fractures can
> lead to an imbalance between the two and result in flow exchange between them
> in the initial state. To achieve an initial balanced flow state, we need to
> set the same non-wetting and
> wetting pressures for both the porous media and fractures, which will result
> in different saturation levels for the two domains.
>
That is right. In order to have capillary equilibrium between matrix and
fractures - for an initial state with non-wetting phase saturations above the
residual saturation - you would have to choose the initial saturations such
that you have capillary pressure equality. That is, you would have to choose
the initial wetting-phase saturations S_w such that pc_matrix(S_{w, matrix}) =
pc_fracture(S_{w, fracture}).
I am assuming that you are neglecting gravitational forces? Because with
gravity your initial state (again, with initial non-wetting phase saturations
exceeding the residual saturations) will not be in equilibrium, anyway, due to
buoyancy - unless your two fluids have the same density.
> While working with COMSOL, I encountered difficulties in achieving a balanced
> initial state. Thus, I am interested in exploring the settings available in
> Dumux-3 to see how it provides a solution to this issue.
>
I hope this helps, and if not, can you maybe provide more details on your
setup, the initial state and what you would like to achieve?
Best wishes,
Dennis
> On 24. Mar 2023, at 11:37, Tianran Ma <[email protected]> wrote:
>
>
> Dear Dumux developers,
>
>
> I am writing to inquire about the capillary setting of the discrete fractured
> model in Dumux-3.
>
>
> I am currently working on verifying a two-phase flow in a fracture model
> based on the paper titled "A discrete fracture model for two-phase flow in
> fractured porous media”. As part of my research, I am comparing
> simulation results between COMSOL Multiphysics and Dumux-3.
>
>
> In my model, the fracture equations and matrix equations are described
> separately and coupled, where both wetting and non-wetting
> pressures/saturation exist in both the matrix and fracture. I understand that
> assigning the same saturation for both the porous media and fractures can
> lead to an imbalance between the two and result in flow exchange between them
> in the initial state. To achieve an initial balanced flow state, we need to
> set the same non-wetting and
> wetting pressures for both the porous media and fractures, which will result
> in different saturation levels for the two domains. However, injecting or
> producing fluids can immediately disrupt this balance.
>
>
> While working with COMSOL, I encountered difficulties in achieving a balanced
> initial state. Thus, I am interested in exploring the settings available in
> Dumux-3 to see how it provides a solution to this issue.
> I have been confused about the initial setting for two-phase flow in
> fractured porous media for a long time. It would be greatly appreciated if
> you could share how you addressed these settings.
>
>
> Thank you for your time and consideration.
>
>
> Best wishes,
>
>
> Tianran Ma
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