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# Estimating multiple time-dependent rates from the same source?

I'm attempting to estimate two time-dependent rates from a heat source/sink, but it appears only to allow estimates of the first one that's listed in the iT2 input file.  My example is as follows:

>> RATE

>>> SOURCE: RSH_1

>>>> INDEX: 1

>>>> GUESS: -0.5

>>>> VARIATION: 0.25

<<<<

>>> SOURCE: RSH_1

>>>> INDEX: 2

>>>> GUESS: -0.75

>>>> VARIATION: 0.25

<<<<

<<<

<<

When I attempted the commands above, the rate from INDEX: 1 changes, while that of INDEX: 2 remains constant throughout the iT2 calculations.

I also attempted created a new second level >> RATE command entry and including everything under the third level >>>> SOURCE entry, all to no avail.  Is there a way to provide an independent estimate of each rate, or do I need to use the >>>> FACTOR command and keep the ratio of the two rates fixed?

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• Ok, this was my mistake.  The syntax about works fine.  The issue I had was with MOP(12), which I mistakenly had set at 2 (strict piece-wise continuous rates), when I thought I had it set at 0 (triple linear interpolation).  The second of my time-dependent rates (INDEX: 2) was set at the last time of the  simulation, so it had no effect on the model results under MOP(12) = 2.

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• Hi Mikey,

I'm glad you figured it out. In general, it is a good idea to separately assess what iTOUGH2 does with the adjustable input parameters, and what the corresponding TOUGH2 response is. In your case, iTOUGH2 properly updated the time-dependent generation rate, and TOUGH2 properly used these values and did what it was instructed to do according to the chosen value of MOP(12). In fact, seeing a zero sensitivity to a change of the second generation rate can be used as an indication that the interpolation scheme may not be what you want it to be - iTOUGH2 thus helps identify issues in the forward input file.

Best,

Stefan

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