# Add parameter on Advection-diffusion problem

**URL:** <https://festim.discourse.group/t/add-parameter-on-advection-diffusion-problem/41>\
**Category:** User Support\
**Created:** [April 26, 2024, 2:55am UTC](https://festim.discourse.group/t/add-parameter-on-advection-diffusion-problem/41 "2024-04-26T02:55:55Z")\
**Posts on this page:** 6\
**Page:** 1

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**Author:** ![RaphaelCSIR](https://yyz2.discourse-cdn.com/free1/user_avatar/festim.discourse.group/raphaelcsir/32/19_2.png) [@RaphaelCSIR](https://festim.discourse.group/u/RaphaelCSIR)\
**Post date:** [April 26, 2024, 2:55am UTC](https://festim.discourse.group/t/add-parameter-on-advection-diffusion-problem/41/1 "2024-04-26T02:55:55Z")

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Hi,

I’m working on geological problem and I try to solve a gas transport across a soil.  
To solve this problem, I want to modify the advection-diffusion equation and by the Fick law (diffusive transport) with porosity and permeability.  
Also, I want to add the gas viscosity, and the pressure.  
How can I perform?

(Moreover, do you know where I can find this file : h\_transport\_problem.F ?)

Thanks!

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**Author:** ![remidm](https://yyz2.discourse-cdn.com/free1/user_avatar/festim.discourse.group/remidm/32/4_2.png) [@remidm](https://festim.discourse.group/u/remidm)\
**Post date:** [April 26, 2024, 11:50am UTC](https://festim.discourse.group/t/add-parameter-on-advection-diffusion-problem/41/2 "2024-04-26T11:50:48Z")

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Welcome @RaphaelCSIR

I think this could be possible. However it is hard to assist you without the mathematical formulation you are trying to solve

Could you provide the PDE representing your problem?

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**Author:** ![remidm](https://yyz2.discourse-cdn.com/free1/user_avatar/festim.discourse.group/remidm/32/4_2.png) [@remidm](https://festim.discourse.group/u/remidm)\
**Post date:** [April 26, 2024, 11:51am UTC](https://festim.discourse.group/t/add-parameter-on-advection-diffusion-problem/41/3 "2024-04-26T11:51:55Z")

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> [@RaphaelCSIR](#):
>
> (Moreover, do you know where I can find this file : h\_transport\_problem.F ?)

This is not a file but an attribute of the problem class

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<div class="post-metadata">

**Author:** ![RaphaelCSIR](https://yyz2.discourse-cdn.com/free1/user_avatar/festim.discourse.group/raphaelcsir/32/19_2.png) [@RaphaelCSIR](https://festim.discourse.group/u/RaphaelCSIR)\
**Post date:** [April 29, 2024, 2:40am UTC](https://festim.discourse.group/t/add-parameter-on-advection-diffusion-problem/41/4 "2024-04-29T02:40:20Z")

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Yes of course!  
 ![Capture d'écran 2024-04-29 043757](https://global.discourse-cdn.com/free1/uploads/festim/original/1X/11b91d1a6c7e3dc0050ca43bb9ea6341bab979cc.png)  
where P is the atmospheric pressure, k the soil permeability and u the hydrogen viscosity.

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<div class="post-metadata">

**Author:** ![RaphaelCSIR](https://yyz2.discourse-cdn.com/free1/user_avatar/festim.discourse.group/raphaelcsir/32/19_2.png) [@RaphaelCSIR](https://festim.discourse.group/u/RaphaelCSIR)\
**Post date:** [April 29, 2024, 2:41am UTC](https://festim.discourse.group/t/add-parameter-on-advection-diffusion-problem/41/5 "2024-04-29T02:41:13Z")

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So how can I modified the advection-diffusion equation to fit with mine?  
Thanks!

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<div class="post-metadata">

**Author:** ![remidm](https://yyz2.discourse-cdn.com/free1/user_avatar/festim.discourse.group/remidm/32/4_2.png) [@remidm](https://festim.discourse.group/u/remidm)\
**Post date:** [April 29, 2024, 11:15am UTC](https://festim.discourse.group/t/add-parameter-on-advection-diffusion-problem/41/6 "2024-04-29T11:15:40Z")

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What is the \varphi variable here?