Inquiry on Boundary Condition Settings in GENERAL Mode

[Zhuoran Du]

Dear PFLOTRAN development team and community,

I am currently working on a research project simulating the oxidation of pyrite in a surface waste rock pile caused by precipitation infiltration. To properly couple unsaturated flow with oxygen transport, I am using the GENERAL mode in PFLOTRAN.

As a first step, I aim to construct unsaturated flow model that allows both vertical and horizontal movement. The conceptual boundary condition setup is as follows:

• Top boundary: precipitation recharge via liquid flux (Neumann);

• Right boundary: constant head via LIQUID_PRESSURE (Dirichlet);

• Left and bottom boundaries: no-flow (zero-flux Neumann).

However, after multiple attempts, the model either fails to converge, or lacks obvious lateral flow even when convergence is achieved.

I have attached two input files for your reference:

• 1.txt: based on the above conceptual model but fails to run;（https://drive.google.com/file/d/19WYfS0WQqFNAU72OwkgMeYo50ycqOTIS/view?usp=sharingtxt txt txt ）

• 2.txt: a simplified version that can run, but no lateral discharge occurs on the right boundary.

I would like to kindly ask the following:

• How should the initial and boundary conditions be correctly configured in GENERAL mode to allow unsaturated lateral flow?

• How can my attached input files be modified to achieve this objective?

As I am still learning PFLOTRAN, I would greatly appreciate your suggestions or guidance.

Thank you very much for your time and support!

Sincerely,
Zhuoran Du

[Hammond, Glenn E]

Zhuoran,

 

I will attempt to look at your input files when I have some free time. In the meantime, I highly recommend (1) setting up your flow problem using RICHARDS mode, (2) add reactive transport, and (3) transition to GENERAL mode. RICHARDS mode is much easier to setup and run than GENERAL.

 

Glenn

 

From: pflotra...@googlegroups.com <pflotra...@googlegroups.com> on behalf of Zhuoran Du <duzr...@gmail.com>
Date: Thursday, June 12, 2025 at 9:24 PM
To: pflotran-users <pflotra...@googlegroups.com>
Subject: [pflotran-users: 8431] Inquiry on Boundary Condition Settings in GENERAL Mode

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[Zhuoran Du]

Dear Glenn,

Thank you very much for your helpful suggestions and for taking the time to look into my input files when you have a chance.

I appreciate your recommendation to start with RICHARDS mode, then add reactive transport, and finally move to GENERAL mode. 

Best regards,
Zhuoran