Help – Volume Balance (Lateral Flows)

[Zain]

Hello,

Well, i am facing an odd issue and i would highly appreciate a help on it.

I am doing an unsteady analysis in a canal reach and have about 17 lateral structures.

When i open my model lateral structures, the volume balance i get at the end of simulation using DETAIL OUTPUT FILE is not correct i.e.

US INFLOW DS OUTFLOW Diversions (lateral)
7111 681 8350

The diversions volume are more than the inflows which is illogical.

The overall error i get is -0.0454% after incorporating storage but the first statement i have written above (US INFLOW AND DIVERSIONS), its illogical. When i close the lateral structures, volume balance becomes okay but as soon lateral structures are included, balance goes out.

Any help / suggestions

Regards
Nayyar Asif

[Zain]

I think i kind of sorted it out.

Hello,

The issue was with the water balance

US INFLOW DS OUTFLOW Diversions (lateral)
7111 681 8350

Initial conditions were simulated that provided the channel with an initial volume. This volume is in addition to the Inflow we are supplying as an input hydrograph. This initial volume is written as START REACH VOLUME in the text file.

When the simulation terminates, there is still water inside the channel. This is called the FINAL REACH VOLUME. The difference between the two is the volume utilized by the lateral structures.

So (US INFLOW + ALREADY PERSENT VOL DIFFERENCE) – DS OUTFLOW – Diversions) should be equal to zero.

I hope my understanding is correct .

Regards
Nayyar

[Anuradha Rout]

Hello Nayyar

i have the same issue, can i ask you where i can find the START REACH VOLUME??
thank you very much
Andrea

[Alquier]

You should go to the Unsteady Flow Analysis Window, Options> View Computation Log File.

That’s very handy to check the mass balance of your model.
If you have issues, it also helps you to know where to start looking for bugs.
However i don’t understand how ras calculates the error.

Does somebody know what is the literal formula used for the error?

[Anuradha Rout]

Hi Alquier

Thank you very much! very interesting data from Computation Log File, but still i don’t get what INITIAL 1D VOLUME and FINAL 1D VOLUME is. how can i check my mass balance?
thank you
Andreea

[Author]

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