Convergence Problem (Soil Column Model)

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Convergence Problem (Soil Column Model)

Post by ES_92 » Thu Feb 25, 2021 7:56 am

Dear all,
I have set up a soil column model in Hydrus 2D to simulate the wetting front behavior of a porous pipe in sandy soil. The model has no flow boundary on three sides and free drainage at the bottom section. The pipe (circle) has constant flux boundary. The initial soil water content was assumed equal to residual water content. I want to simulate it for 72 hours and I have chosen the initial time, minimum and maximum time as 1 hour. But when I run the model it says "Numerical solution has been stopped since it has not converged in 10 consecutive time steps !" I tried with other different time but still it did not work out.
It will be a great help if any of you can let me know how should I solve this problem. I have also attached the model. Waiting eagerly for the response. Thank you.
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Re: Convergence Problem (Soil Column Model)

Post by Jirka » Thu Feb 25, 2021 6:28 pm

I have quickly looked at your project. There are some really trivial errors, which I would hope a Hydrus user would avoid:
1. The "Minimum allowed time step" needs to be smaller than or equal to the "Initial time step". The default and recommended values are very different from those that you use.
2. You clearly cannot have the initial condition equal to the residual water content, since then the pressure head is negative infinity.

You should consider doing some HYDRUS tutorials (e.g., on drip irrigation, or take a Hydrus short course to avoid errors like these.

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