## Constant Pressure Head in Hydrus 2D

A discussion forum for users of the new HYDRUS 2D/3D. HYDRUS is a software package for simulating water, heat and solute movement in two- and three-dimensional variably saturated media. Happy Posting!
ES_92
Posts: 19
Joined: Sun Dec 06, 2020 11:22 am
Location: Italy

### Constant Pressure Head in Hydrus 2D

I am simulating my 2D model for constant head boundary condition. In my initial condition I defined the initial head for sandy soil as -3774 cm and for boundary condition of the porous pipe I defined the working pressure head as -600 cm. But when I simulate it the wetting front is too small which seems a bit strange. Am I doing something wrong? I also have attached the model. Any suggestion will be really helpful. Thanks
Attachments
Sand.zip
CH2.PNG (30.31 KiB) Viewed 452 times
CH1.PNG (27.21 KiB) Viewed 452 times

Jirka
Posts: 5268
Joined: Sat Mar 16, 2002 3:47 pm
Location: USA
Location: Riverside, CA

### Re: Constant Pressure Head in Hydrus 2D

I wonder if you fully understand what you are trying to simulate.
1. While you defined the initial pressure head of -3774 cm, you actually did not assign it to the transport domain. Note that it is still dark blue (i.e., h=-100 cm). You need to click on the second initial condition and then the transport domain, to actually assign it.
2. Even if you do that, why would you expect that you get much infiltration. The conductivity corresponding to the boundary pressure head h=-600 cm is about 1.e-11 cm/h and that’s clearly a minuscule flux. You will start seeing some infiltration only when your boundary pressure head is larger than about – 10 cm.
J.

ES_92
Posts: 19
Joined: Sun Dec 06, 2020 11:22 am
Location: Italy

### Re: Constant Pressure Head in Hydrus 2D

Dear Prof. Jirka,
Thank you very much for your response.
I am trying to simulate the infiltration rate in different types of soil by using constant head boundary. Previously I was using constant flux boundary but then infiltration rate will be independent of the system. But I could see the infiltration happening (it was same for every type of soil). The discharge is 1.3 l/h/m which translates into 4.14 cm flux and the corresponding pressure to the discharge is 60 kPa. That is why I simulated the model using -600 cm. Now, I am wondering which way should I proceed to simulate different infiltration rates in the soil, as I need to plan an experiment based on the simulation result. Your suggestion will be very helpful.

Jirka
Posts: 5268
Joined: Sat Mar 16, 2002 3:47 pm
Location: USA
Location: Riverside, CA

### Re: Constant Pressure Head in Hydrus 2D

Why don’t you try different boundary pressure heads to see their impact on the infiltration rates in different soil materials? J.