numerical solution is not converged

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hyein
Posts: 1
Joined: Sun May 17, 2020 5:11 pm
Location: Korea

numerical solution is not converged

Post by hyein » Mon May 18, 2020 3:58 am

Hi.
I hav some problems in my simulation.
why the numerical solution is not converged in my simulation??
my hydraulic parameter is 0.025 0.947 0.062 1.031 144.7 0.5 for van Genuchten model.
THe file is not attached in this page....
I can't find the reason.....

also, There is something I really want to know about soil hydraulic parameter, but I haven't found the answer.
What exactly is the range of residual water content and saturated water content when using the Van Genuchten model?
I thought its shouldn't go over 1, but using an inverse solution, the optimized saturated water content was over 1.
I'm looking foward to your refly soon.
It is very important to me.
Thank you.

Jirka
Posts: 4922
Joined: Sat Mar 16, 2002 3:47 pm
Location: USA
Location: Riverside, CA

Re: numerical solution is not converged

Post by Jirka » Mon May 18, 2020 4:02 pm

When you have the n parameter less than 1.1, you should use the VGM model with an air-entry value of -2 cm, since the standard VGM model provides erroneous predictions of the conductivity function (for fine-textured soils with low n values).

The inverse algorithm does not check the physical correctness of optimized parameters. It is up to the users to specify reasonable physical constraints. If the optimized value of theta_s goes over 1, then clearly your dataset does not contain enough information to fit this parameter and it should not be optimized, but should be fixed to some measured or estimated value.

J.

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