Wrong output concentration

A discussion forum for Hydrus-1D users.
Post Reply
yarivts
Posts: 9
Joined: Mon Jul 10, 2017 2:25 pm
Location: Israel

Wrong output concentration

Post by yarivts » Wed Dec 26, 2018 2:41 pm

Hello,
I'm trying to model a recovery treatment for a contaminated layered soil (20 m profile). My goal is to examine whether the existing pollutant will flushed down to the groundwater during the treatment. For simplification, the adsorption, diffusion and Henry coefficients were set to zero. The dispersion was set to 200 cm. Atmospheric b.c was set, applying 12 cm of rain during the first 4 days with zero evaporation and zero c top/bottom. Finally, I have specified the pollutant concentration along the soil profile (1.7e-5 g/cm3 at the depths of 0.5-2 m). However, the initial concentration at the results are very different from what i"ve specified (orders of magnitude larger). In addition, the relative error was close to zero.
Any solution or explanation for that problem will be helpful.
Many thanks,
Yariv

Jirka
Posts: 4726
Joined: Sat Mar 16, 2002 3:47 pm
Location: USA
Location: Riverside, CA

Re: Wrong output concentration

Post by Jirka » Wed Dec 26, 2018 3:50 pm

Not enough information. J.

yarivts
Posts: 9
Joined: Mon Jul 10, 2017 2:25 pm
Location: Israel

Re: Wrong output concentration

Post by yarivts » Thu Dec 27, 2018 6:31 am

Hey, I have solved the problem. The problem was with specifying the initial condition in in total concentrations.
Thanks

yarivts
Posts: 9
Joined: Mon Jul 10, 2017 2:25 pm
Location: Israel

Re: Wrong output concentration

Post by yarivts » Thu Dec 27, 2018 6:44 am

By the way, is there any good example on the website for transport of hydrocarbons/solute with high adsorption values?
Yariv

faith1796
Posts: 8
Joined: Sat Apr 27, 2019 9:03 am
Location: China

Re: Wrong output concentration

Post by faith1796 » Tue May 14, 2019 6:26 am

Hello, friend. I have met the same problem, the mass unit I set was gram, while the length unit was meter. The initial concentration for COD was set as 52 [-]. But the result time series started from 2000 g/m3. Could you share the solution with this problem please? Thanks in advance.

Jirka
Posts: 4726
Joined: Sat Mar 16, 2002 3:47 pm
Location: USA
Location: Riverside, CA

Re: Wrong output concentration

Post by Jirka » Tue May 14, 2019 2:20 pm

It is impossible that HYDRUS-1D would start calculations with different initial concentrations in the liquid phase that those specified, unless you used the option to specify the initial conditions in terms of Total Concentrations, rather than in Liquid Phase Concentrations. In such case, HYDRUS-1D will distribute specified values (total concentration) among different phases (liquid, solid, and gaseous) based on specified coefficients (Kd, Kh, Beta, eta). J.

faith1796
Posts: 8
Joined: Sat Apr 27, 2019 9:03 am
Location: China

Re: Wrong output concentration

Post by faith1796 » Fri May 17, 2019 3:17 am

Jirka wrote:
Tue May 14, 2019 2:20 pm
It is impossible that HYDRUS-1D would start calculations with different initial concentrations in the liquid phase that those specified, unless you used the option to specify the initial conditions in terms of Total Concentrations, rather than in Liquid Phase Concentrations. In such case, HYDRUS-1D will distribute specified values (total concentration) among different phases (liquid, solid, and gaseous) based on specified coefficients (Kd, Kh, Beta, eta). J.
I am using hydrus 2D to simulate. Yes, I specify the initial conditions in terms of total concentration. however, it still can't explain why the starting concentration is so much higher than the initial condition. Any clue or hint on that? Thanks

Jirka
Posts: 4726
Joined: Sat Mar 16, 2002 3:47 pm
Location: USA
Location: Riverside, CA

Re: Wrong output concentration

Post by Jirka » Fri May 17, 2019 2:05 pm

I have no more to add to this topic. J.

Post Reply