Implementation of scaling factors

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matt_patt30
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Joined: Tue May 05, 2015 5:17 pm
Location: USA

Implementation of scaling factors

Post by matt_patt30 » Mon Feb 03, 2020 8:00 pm

Hello,

I'm utilizing a map of scaling factors that I have imported into HYDRUS 3D and I had a question about how they are implemented. I saw in the technical manual, and some literature, that the scaling factors are taking reference hydraulic functions (defined by the retention and conductivity parameters for each material) and multiplying them by the scaling factors at each node, but where they are implemented into the calculation procedure is a little vague. Are the scaling factors applied before or after the calculations for each time step? In other words, are they modifying the hydraulic properties at each point before the result for each time step is calculated, or taking the calculated result for each point and multiplying them by their respective scaling factors? The former makes more sense, but I just want to make sure.

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

Re: Implementation of scaling factors

Post by Jirka » Mon Feb 03, 2020 9:38 pm

The former. Scaling factors modify the soil hydraulic properties, which are used to solve the Richards equation, i.e., they are used before the discretized matrix equation is assembled. J

matt_patt30
Posts: 12
Joined: Tue May 05, 2015 5:17 pm
Location: USA

Re: Implementation of scaling factors

Post by matt_patt30 » Mon Feb 03, 2020 10:56 pm

Great. Thanks for the quick reply! Is there a way to see what the modified hydraulic properties are for each observation node before the calculations? There are outputs of water retention (theta and h) for the observation nodes in OBSNOD.OUT, but those are from after the calculations correct? If so, I have noticed in this example run I did where I used only scaling factors for the pressure potential that the pressure potential values in the HYDRUS GUI output and the OBSNOD.OUT file do not match up (see attached at t=1000). I thought maybe that was due to the scaling factor for that particular node, but it still does not make sense since the scaling factor for that particular node is 1.10. It may seem overboard, but I want to understand what exactly the scaling factors are doing within the model
Attachments
OBSNOD comparison.png
OBSNOD comparison.png (209.46 KiB) Viewed 78 times

Jirka
Posts: 4847
Joined: Sat Mar 16, 2002 3:47 pm
Location: USA
Location: Riverside, CA

Re: Implementation of scaling factors

Post by Jirka » Mon Feb 03, 2020 11:45 pm

When HYDRUS GUI makes the graph for observation nodes, it reads values directly from the ObsNode.out file. The value in the graph and in the output files cannot be different, that's impossible. J.

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