Variable flux to simulate wicking of water into soil

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ahmed_almayahi
Posts: 19
Joined: Tue Jun 12, 2018 12:49 pm
Location: Oman

Variable flux to simulate wicking of water into soil

Post by ahmed_almayahi » Tue Dec 11, 2018 7:52 am

Dear HYDRUS experts
I am trying to model water and solute transport in a silt loam soil irrigated via wicking from the bottom using HYDRUS 2D. I assigned var.flux2 bc for the wicking point at the bottom of the soil. I intended to simulate irrigation via wicking every 3 days [1 day irrigation via wicking, 3 days no wicking]. When there is a wicking, the flux is -86.035 cm/day and when is no wicking the flux is zero cm/day. However, when i run the calculation, hydrus did not give me any results. When i tried to changed the flux.var 2 to contast head of 3 cm, i obtained results. I red the manual, looked at the examples posted https://www.pc-progress.com/en/Default. ... cations#k3 and https://www.pc-progress.com/en/Default. ... d-lib-drip and i could not find a way to solve the problem. could you please help me to understand the problem and how to solve it?

I attached the hydrus file and an image to show you the domain and bc of my project

Looking forward to hear from you

Regards
Attachments
2d salinity .rar
(142.01 KiB) Downloaded 10 times
Prob_vari_flux.png
Prob_vari_flux.png (343.1 KiB) Viewed 573 times

Jirka
Posts: 4563
Joined: Sat Mar 16, 2002 3:47 pm
Location: USA
Location: Riverside, CA

Re: Variable flux to simulate wicking of water into soil

Post by Jirka » Tue Dec 11, 2018 5:16 pm

I cannot open your project. It seems to be corrupted. Start with smaller fluxes to see if the set up works. Note that the applied flux should not be higher than Ks of the soil. J.

ahmed_almayahi
Posts: 19
Joined: Tue Jun 12, 2018 12:49 pm
Location: Oman

Re: Variable flux to simulate wicking of water into soil

Post by ahmed_almayahi » Wed Dec 12, 2018 4:21 am

Dear prof
I tried to do 3 different things :
1. set a variable flux <ks for the soil
2. use the same value of the flux through all the simulation time. In this condition the variable flux is constant.
3. i was also suspecting that the problem could be due to the sign (-/+) of the flux although the manual said that "use negative values for inflow flux into the soil", so i tried to use both conditions one time simulation with positive flux and then another simulation with negative flux.
All trails did not work

I created a new project and attached here, maybe this could be more helpful to investigate the problem

Regards
Attachments
Salinity2d.rar
(155.77 KiB) Downloaded 8 times

Jirka
Posts: 4563
Joined: Sat Mar 16, 2002 3:47 pm
Location: USA
Location: Riverside, CA

Re: Variable flux to simulate wicking of water into soil

Post by Jirka » Wed Dec 12, 2018 6:04 pm

Since you have infiltration into a very dry sand (note that the water content of a sand for the pressure head of -1000 cm is practically the residual water content) you need to allow smaller time steps. I have simply lowered the initial and minimum time steps and the program ran just fine. J.
Salinity2d.rar
(559.3 KiB) Downloaded 8 times

ahmed_almayahi
Posts: 19
Joined: Tue Jun 12, 2018 12:49 pm
Location: Oman

Re: Variable flux to simulate wicking of water into soil

Post by ahmed_almayahi » Wed Dec 12, 2018 8:31 pm

That really solve the problem

Thanks

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