flow atmospheric boundary cycle

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Naomi
Posts: 4
Joined: Wed Feb 13, 2019 2:48 pm
Location: Israel

flow atmospheric boundary cycle

Post by Naomi » Thu Feb 14, 2019 9:05 am

Hello,

I have an 2D axisymmetrical domain, radius 30 m, height 30 m, homogeneous sand .
The model is solute transport, the solute source is from 5 m line (which means circle radius 5 m) at the center of top boundary (1st-type BC, 1 kg/m^3 for all times variable).
The top flow BC is atmospheric, the data is precipitation rate and potential evaporation rate for one year (365 times variable).
The bottom flow BC is constant pressure head - 0.

In order to get pressure head initial condition, I run the program without solute for 5 years until theta in soil became equilibrium.
At this run the cycle of flux from atmospheric boundary is OK - repeated every 365 days.

The problem begin when I insert the solute transport to model, for no apparent reason, the cycle of flux from atmospheric boundary grow to two years - 730 days. The different between the two years is one order (in odd years the biggest flux is -0.03 m/day, in double years the biggest flux is -0.17 m/day).
I tried to insert another precipitation and evaporation data but it was not change..
Any ideas why its happend and how can I fix it?
(at cumulative atmospheric flux curve I don't see different between consecutive years, maybe the quantity is not significant..)

And one more question - at the curve "atmospheric solute flux", at the times there are actual evaporation, the solute flux is positive (to size ~0.2 kg/day). How can it be? the evaporation take only water and no solute, or that I have misunderstanding here..

Thank!!

Jirka
Posts: 4597
Joined: Sat Mar 16, 2002 3:47 pm
Location: USA
Location: Riverside, CA

Re: flow atmospheric boundary cycle

Post by Jirka » Thu Feb 14, 2019 7:19 pm

If you post your project, I will have a look at it. Otherwise, I have no useful comments. J.

Naomi
Posts: 4
Joined: Wed Feb 13, 2019 2:48 pm
Location: Israel

Re: flow atmospheric boundary cycle

Post by Naomi » Sun Feb 17, 2019 8:49 am

Now I attached the project file.
Because of the size limit, I run the project for four years so the concentration is not in equilibrium (it's take ~11 years).

thank you,
Naomi
Attachments
cycle project.zip
(1.82 MiB) Downloaded 2 times

Jirka
Posts: 4597
Joined: Sat Mar 16, 2002 3:47 pm
Location: USA
Location: Riverside, CA

Re: flow atmospheric boundary cycle

Post by Jirka » Sun Feb 17, 2019 6:44 pm

Hi Naomi,

You state this: " For no apparent reason, the cycle of flux from atmospheric boundary grow to two years - 730 days. The different between the two years is one order (in odd years the biggest flux is -0.03 m/day, in double years the biggest flux is -0.17 m/day)."

Are you looking at the Boundary fluxes graph? Note that you requested output each 10 days, and thus you get outputs at 10, 20, …. 360, 370, 380 …. etc days. I.e., you get output fluxes for different days in odd and even years. If you choose output each day (or each time step), you would see exactly the same pattern each year (as you can see in the cumulative fluxes).

J.

Naomi
Posts: 4
Joined: Wed Feb 13, 2019 2:48 pm
Location: Israel

Re: flow atmospheric boundary cycle

Post by Naomi » Mon Feb 18, 2019 9:54 am

Hi Jirka,

While the software run its show numbers for all days so I thought that the graphs show results for every day.
Thank you!

Do you have any explanation to my second question:
'at the curve "atmospheric solute flux", at the times there are actual evaporation, the solute flux is positive (to size ~0.2 kg/day). How can it be? the evaporation take only water and no solute, or that I have misunderstanding here..'?

Naomi

Jirka
Posts: 4597
Joined: Sat Mar 16, 2002 3:47 pm
Location: USA
Location: Riverside, CA

Re: flow atmospheric boundary cycle

Post by Jirka » Mon Feb 18, 2019 7:12 pm

I’m currently traveling in Europe and do not have time to look at your project again. However, I recall that you used the Dirichlet BC for solute transport. That is almost always a wrong selection since then you cannot control the dispersive flux, which may be directed either in or out of the domain (which may be unphysical). We almost never recommend to use the Dirichlet BC, you should almost always (and certainly at the soil surface exposed to atmospheric BC) use the Cauchy BC for solute transport. J.

Naomi
Posts: 4
Joined: Wed Feb 13, 2019 2:48 pm
Location: Israel

Re: flow atmospheric boundary cycle

Post by Naomi » Wed Feb 20, 2019 10:09 am

OK I'll check the two options. Thank you

Enjoy your travels :)

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